The first product, which is already available for order, is a plastic case for the popular Raspberry Pi Pico W microcontroller with straight pin headers.

Just like IoT-devices’ own products, the items under the IoT Case Lab brand are supplied by the company under the same terms and policies, with global shipping available.

Customers from over 40 countries can already place orders on the website’s store. There are also plans to list the ICL-branded products in the IoT-devices LLC store on the Etsy marketplace.

A Product That Solves Problems

ICL products address common issues that DIY developers constantly face. The most popular components are typically connected using Dupont cables, which have a significant flaw: they often have a loose fit, leading to unstable connections and potential project failures.

The engineers at IoT Case Lab took this problem into account and designed a case that not only protects the microcontroller from external damage and short circuits but also securely fastens the Dupont connectors. This ensures a stable connection and makes the device easy to use.

Key Features of the case line:

• Specialized Design: The cases are specifically designed for certain microcontroller models, in this case, the Raspberry Pi Pico W with straight pin headers.
• Secure Connection: Dupont cable connectors are firmly secured by a panel, preventing them from accidentally disconnecting.
• Full Functionality: All pin headers, the BOOTSEL button, the Debug port, and the micro-USB port remain fully accessible.
• Protection and Cooling: The case protects the controller board from mechanical damage, while ventilation holes provide passive cooling.
• Universal Mounting: Thanks to special universal connectors, ICL cases can be joined with each other.

Details and Links

This case can be ordered on the IoT-devices website via the following link:
https://iot-devices.com.ua/en/product/raspberry-pi-pico-w-icl-rpipw-st-v1-plastic-case-straight/

For those who want to get to know the product better, all information is available on GitHub:
https://github.com/IoTCaseLab/ICL_RPIPW_ST_V1-case-for-Raspberry-Pi-Pico-W-with-straight-pin-headers

3D model of the case’s outer contours: https://github.com/IoTCaseLab/ICL_RPIPW_ST_V1-case-for-Raspberry-Pi-Pico-W-with-straight-pin-headers/blob/main/res/RPi-Pico-W-2022-model_straight_mcu2-type2_solidDemoBrick.stl

Our Idea

Over the past few years, we’ve encountered situations where a Geiger counter needed to be used simply and quickly, without specialized knowledge or experience, without connecting additional devices, and without complex communication. Of course, you could just count pulses and time them with a stopwatch. But we thought, why not create a convenient app for this? And we did.

Benefits of Using GGreg20_V3 with This App

• Affordable Solution: No need for a controller like Arduino, ESP8266, ESP32, or Raspberry Pi.
• Ease of Use: No programming skills required.
• Wireless: No need to solder or connect cables.
• Quick Start: No need to search for or pair a new device.
• Broadcasting: If needed, one Geiger counter can be used simultaneously by many users.

Who This App Is For

While this app isn’t precise and, paired with GGreg20_V3, isn’t a finished device, users who can’t or don’t want to program can immediately use the GGreg20_V3 module simply by powering it and installing this app.

But remember, this is only an educational, demonstration, and testing app for beginners. Please choose appropriate tools for appropriate tasks.

This app is also convenient for quickly testing the module’s functionality, for example, when picking it up at the post office.

For Accurate Measurements

If you’re looking for accurate and reliable measurements using the GGreg20_V3 module, we recommend checking out our other companion app for GGreg20_V3, which is about to appear on Google Play. That app uses a controller with Bluetooth as the data transfer channel between the module and the smartphone.

Please note: the BLE app requires significantly more work on the DIY project – at least knowledge of ESPHome, BLE Server, and controllers like ESP32 or Raspberry Pi Pico W, etc.

How It Works

GGreg20_V3 users only need the module powered (according to documentation) and this smartphone app. Wireless data transfer from the GGreg20_V3 module to your smartphone occurs via sound signals from its built-in buzzer. The app filters sounds captured by the smartphone’s microphone, recognizing only those that match the signals from the GGreg20_V3 buzzer.

Known Limitations

Using the wireless audio channel can lead to false readings or inaccuracies in noisy environments.

Specifically:

• Although the GGreg20_V3 Geiger counter can register all pulses that tubes like J305, SBM20, or LND712 are capable of in high-radiation conditions, this app has a significant limitation. To differentiate pulses, an artificial 70-millisecond delay between the pulses the app perceives had to be implemented. This means the app can correctly process radiation levels only up to 850 CPM (or 3 uSv/hour). This is entirely sufficient for normal household conditions but will be insufficient in the event of a nuclear disaster.
• While the app effectively filters events only of a specific frequency, there’s a problem of signal clutter, for instance, from a nearby conversation. In such cases, the signals overlap, and the app ignores relevant pulses.
• We’re also aware of an echo problem with relevant signals. This occurs in enclosed spaces. You can see this effect in the video in the app description on Google Play, where the buzzer pulses once, but the app sometimes counts them twice, likely due to echo. (For shooting this video, we use a lightbox where the echo occurs.)

Important Note

This app, like the GGreg20_V3 module, is not a precise measuring device. It’s intended for personal use, hobbies, learning, and creative experiments, not as a finished product. It’s created for DIY electronics enthusiasts.

Keywords

Geiger counter, GGreg20_V3, Ionizing Radiation, Companion Application, Conversion Factor, Geiger Muller Tube, DIY, IoT, Radiation Measurement, Embedded Electronics, Electronics

Since each user can choose one of many possible variations of the GGreg20_V3 configuration on the website and on Etsy when ordering, we conduct this analysis every year, because we are always interested in which configurations we need to have in stock the most to meet the needs of our online store users in a timely manner.

We also thought that potential buyers might also be interested in which GGreg20_V3 packages other radio amateurs order most often. So we decided to publish the statistics for the past year.

Option packages are available to order:

What we found this time

GGreg20_V3 Basic + J305 tube + Connectors (installed) and cables + Casing3d

In more than half of the cases, users ordered the complete configuration, which includes the module, the J305 Geiger tube, and two JST-JST and JST-Dupont cables and a protective 3D-printed case.

SKU of the set: ggreg20_v3_basic305_cabcas

GGreg20_V3 Basic + J305 tube + Connectors (installed) and cables

Almost a quarter of the orders included a J305 Geiger tube and cables in addition to the GGreg20_V3 module. Obviously, the casing was either not needed in these orders or the customer was able to print it out on their own, as the STL model of the casing is distributed by IoT-devices for free.

SKU of the set: ggreg20_v3_basic305_cab

GGreg20_V3 Basic + J305 tube

Twelve percent of our orders included the base module with the J305 Geiger tube. It’s surprising that only 12.2% of customers chose this option. We believe it’s the most optimal configuration in terms of price-to-functionality ratio. If you’re looking to save money while getting a fully functional, ready-to-use module, this variation is an excellent choice.

SKU of the set: ggreg20_v3_basic305

GGreg20_V3 basic

In more than seven percent of orders, customers have ordered the GGreg20_V3 module without additional options. We can add that such orders are usually intended to replace an existing Geiger counter module with the GGreg20_V3. Users tell us that they already have the tube and only need the module. Most often, the basic module without options is ordered by radio amateurs who know what they are doing. We also have long-term customers who have already bought modules from us twice, three times, and even four times, for which we are very grateful. We appreciate it and thank them for their trust and support.

SKU of the set: ggreg20_v3_basic

GGreg20_V3 basic + Connectors (installed) and cables

The rest of the orders, which is almost five percent, were for configurations containing the GGreg20_V3 module and cables. It’s good that we made this variation as well, because it was useful to a significant number of our customers.

SKU of the set: ggreg20_v3_basic_cab

Diagram

Table

Note. Please note that the data on replacements and repairs, which also sometimes occurred in 2024, are not included in the statistics we are discussing in this article.

The book is devoted to theoretical foundations and practical experiments with Geiger counters. In particular, the book deals with DIY counters, which are developed by radio amateurs and are quite popular components for various IoT projects.

Thank you for mentioning our projects and company in the book. We are glad to be a part of the community of DIY enthusiasts who managed to release their own product, which has found its users in more than 20 countries around the world.

You can read the book by following the link on the Springer Nature website.

We have previously written about how to calculate the coefficients for the SBM20 tube and the J305, tube that come with our Geiger counter module GGreg20_V3 for DIY / IoT projects.
However, in those articles, we focused heavily on the calculation formulas and almost overlooked a very important detail: when calculating the conversion factor for the Geiger tube pulse count, we need to be aware of what exactly we want to get as the output.

If we need to obtain the radiation power of a radioactive source registered by the counter, this is one task.
It is a completely different task when we need to obtain the equivalent value of the radiation dose absorbed by the human body over a certain period of time.

We describe in detail how to calculate the coefficients in our previous publications, so we will not waste the reader’s time now.
Instead, we will try to show the differences between the calculated coefficients and how best to use them for a DIY project.

The data is provided for the J305 tube. Any other Geiger tube, such as the SBM20 or LN712, can also be used in its place, since they all have a similar principle of operation except for certain nuances that we can neglect for the purposes of this discussion.

In our previous publications, we went from start to finish: we have pulses -> we want to keep the value in μSv/h.
Today we will try to go the other way: from the goal of the DIY project through the sequential steps to achieve it.

As DIY Geiger counter users, we would most likely want to have access to the following information on our device’s display:

1. CPM: The number of registered pulses per minute received from the counter;
2. μSv/h: The radiation power of the source registered by the counter;
3. μSv: The absorbed dose by the human body over a certain period of time.

Take a close look at these values. The secret to calculating them correctly lies not only in the correct formulas and coefficients, but also in understanding the overall process:

• The source emits radiation;
• The counter registers it;
• The human body absorbs it.

The human body does not absorb everything that the counter registers. The counter readings and the absorbed dose are highly dependent on many factors. Therefore, to simplify the measurements, it is common to use ready-made data from the manufacturer and equivalent models for calculating the corresponding coefficients.

Pulse Count

We obtain the pulse count from the Geiger counter module. For convenience of calculations, as well as based on the pulse density during normal background radiation measurements, this parameter is best calculated in counts per minute (CPM).

For example, the J305 manufacturer specifies in the datasheet that the tube should emit 25 pulses per minute under normal background radiation. In other words, 25 CPM.

Why do we need the CPM value on the display if there are other, more understandable indicators? Indeed, it is possible to do without pulses per minute. However, it is a very convenient indicator when we want to understand if there are any malfunctions in the device. Usually, in our devices, we make a cumulative counter of the number of registered pulses for the entire time the device has been operating since the power was applied.

In this case, even if we do not have a source of accurate synchronized time, such as NTP or RTC, we can still calculate the average number of pulses per minute by dividing the sum of all pulses by the total time elapsed since power was applied. This indicator can indicate the quality of our data, even if hours have passed since the device was turned on.

We hope that since the principle of such checks is already known to you, you will develop your own algorithms for checking the data quality and the operation of the counter if necessary. There can be many implementations.

Radiation Source Power

When we want to estimate the radiation source power, we need to apply the conversion factor from CPM to μSv/h obtained by calculation based on the data specified in the tube’s datasheet from the manufacturer:

For the J305 tube, the manufacturer specifies a sensitivity of 44 cpm per 1 μR/h from a Co-60 source;

Let’s convert the data we need:

1. Converting to counts per minute at 1 mR/h:

CPS / mR/h → CPM / mR/h: 44 * 60 = 2640;

2. Converting to counts per minute at 1 μSv/h:

CPM / mR/h → CPM / μSv/h: 2640 / 10 = 264;

3. Value of one pulse per minute in μSv/h:

1 / ( CPM / μSv/hr ) = 1 / 264 = 0.00378;

Therefore, if we need to convert the pulses registered by the J305 tube during a minute to μSv/hour and obtain the radiation source power value:

1 CPM = 0.00378 [μSv/h];

or

When we read the documentation for a Geiger tube, this is the parameter that is usually discussed.

Equivalent Dose Absorbed by the Human Body

To obtain the value of the equivalent dose of radiation absorbed by the human body, we will apply the model of a human body phantom:

1. Lets convert counts per second to counts per minute at 1 mR/h:

44 * 60 = 2640 pulses/minute / mR/hour

2. Convert CPM at 1 mR/h to CPM at 1 R/h:

2640 * 1000 = 2640000

3. Let’s find the value of the exposure dose R/h at 1 CPM:

1 / 2640000 = 0.0000003787878788

4. Find the air-kerma (Ka, kinetic energy released per unit mass/in matter):

The equation is as follows:

Ka [Gy] = 0.00877 [Gy/R] x exposure [R]

where 0.00877 – radiation dose absorption coefficient by the human body on a phantom model under the influence of photon energies of 100 keV – 3 MeV

0.00877 * 0.0000003787878788 = 0.000000003321969697 Ka[Gy]

5. Let’s convert Ka[Gy] to Ka[μSv] (i.e., from Gray to μSv):

0.000000003321969697 * 1000000 = 0.003321969697 Ka[μSv]

Thus, the formula for the equivalent absorbed dose of radiation by the human body for the Geiger-Muller J305 tube with gamma sensitivity for Co-60 of 44 cps/mR/h is as follows:

Please note: To obtain the cumulative value of the equivalent dose of energy absorbed by the human body, we need to add the hourly values to the previous accumulated sum throughout the entire measurement period (from the moment of power supply or resetting the counter value). See the example below.

Why should we be more interested in the dose of radiation absorbed by the human body than in the radiation source power? There are at least two reasons for this, which follow from each other.

First, from the point of view of radiation safety, it is not the power of the source itself that is important, but the dose that we will absorb over a certain period of time if we are exposed to the radiation source.

Second, since the dose of absorbed radiation is so important, it is the dose for humans that is calculated and provided by government organizations for radiation protection and public health.

Usually, the permissible dose is given for a period of one year. It is such tabular data that allows us to objectively assess what is the normal level of background radiation – the moment when the radiation source power and the equivalent dose absorbed by the human body can be converted to common units and compared.

If the normal background level, in terms of its instantaneous power converted to a year, turns out to be higher than the permissible dose per year, then this may not be background, but a certain radioactive source. And then something needs to be done immediately with the radiation source that creates such a “background” so as not to exceed the permissible absorbed dose of radiation by our body.

Practice and Examples

Now we come to the most important thing: when creating sensor entities for GGreg20_V3 with a J305 tube, for example in ESPHome, we need to use the appropriate coefficients for different physical values.

1. Number of pulses per minute is always just the number of pulses – a dimensionless value. But if necessary, a conversion or averaging coefficient can also be applied (not considered in this article);
2. For radioactive source power: CPM * 0.00378 [μSv/h];
3. For the equivalent dose absorbed by the human body: CPM x 0.00332 [μSv/h], finding the sum of the minute-by-minute values [μSv] for the entire measurement time.

Example for ESP32 + GGreg20_V3 + J305 у ESPHome

# 1. Pulse Count Sensor from a Counter with a 60-Second Measurement Cycle

 sensor:
- platform: pulse_counter
 pin:
 number: 23
 inverted: True
 mode: 
 input: True 
 pullup: False
 pulldown: False
 unit_of_measurement: 'CPM'
 name: 'Ionizing Radiation CPM'
 count_mode: 
 rising_edge: DISABLE
 falling_edge: INCREMENT # GGreg20_V3 uses Active-Low logic
 use_pcnt: False
 internal_filter: 180us # for J305
 update_interval: 60s
 accuracy_decimals: 0
 id: my_cpm_meter

# 2. Radiation Source Power Sensor with a 60-Second Measurement Cycle

- platform: copy
 source_id: my_cpm_meter
 unit_of_measurement: 'uSv/Hour'
 name: 'Ionizing Radiation Power'
 accuracy_decimals: 3
 id: my_power_meter
 filters:
 - multiply: 0.00378 # for J305

# 3. Sensor for Equivalent Dose Absorbed by the Human Body per Hour with a 60-Second Measurement Cycle

- platform: copy
 source_id: my_cpm_meter
 unit_of_measurement: 'uSv/Hour'
 name: 'Ionizing Radiation Equivalent Absorbed Energy'
 accuracy_decimals: 3
 id: my_dose_meter
 filters:
 - multiply: 0.00332 # for J305

# 4. Cumulative Equivalent Dose Absorbed by the Human Body from Radiation Since the Start of Measurement (i.e., from the Moment of Power Supply)

- platform: integration
 name: "Total Ionizing Radiation Equivalent Absorbed Energy Dose"
 unit_of_measurement: "uSv"
 sensor: my_dose_meter # link entity id to the pulse_counter values above
 icon: "mdi:radioactive"
 accuracy_decimals: 5
 time_unit: min # integrate values every next minute
 filters:
 # cumulative absorbed dose. Converting it from uSv/hour into uSv/minute: [uSv/h / 60] OR [uSv/h * 0.0166666667]. 
 - multiply: 0.0166666667
 # but if my_dose_meter in CPM, then [0.00332 / 60 minutes] = 0.000055; so CPM * 0.000055 = dose every next minute, uSv.
 #- multiply: 0.000055 # for J305

Conclusions

In this article, we made an important discovery that the coefficients for different tasks for the same Geiger tube should be different. This approach differs from the examples that are given on the Internet.

Although we have already written in passing about different coefficients (see articles on calculating conversion coefficients), in our numerous examples on GitHub , we previously used only one coefficient, because that’s what everyone does.

Now we believe that it is better to calculate a separate coefficient for each sensor entity depending on its type and purpose. Perhaps we will even update the YAML files in our examples on GitHub.

References to other publications and examples

UA: Geiger tube J305: How to calculate the conversion factor of CPM to μSv/h Technical note
EN: Geiger tube J305: How to calculate the conversion factor of CPM to μSv/h. Technical note

UA: Технічна нотатка: Як розрахувати коефіцієнт перетворення для трубки Гейгера СБМ20
EN: Technical note: How to calculate the conversion factor for Geiger tube SBM20

UA: Трубки Гейгера-Мюллера: порівняння SBM20, J305 та LND712
EN: Geiger-Muller tubes: Comparison of SBM20, J305 and LND712

EN: DIY Geiger counter GGreg20_V3 on GitHub

Easy Links

Unique Vendor ID: https://go.iot-devices.com.ua/ggreg20_v3
User Friendly ID: https://go.iot-devices.com.ua/geiger-counter

Where and how to order

Website Online Shop
Etsy Store
Tindie Marketplace

Dear users, customers and partners!

We are pleased to announce that with the launch of Etsy Payments service in Ukraine, we immediately opened our own official store on this wonderful platform for DIY.

Now you can order the company’s products on Etsy or Tindie, as well as on our website. With the launch of Etsy Payments in Ukraine, our visitors and regular customers can choose any convenient and secure payment method such as bank cards, PayPal, etc. As an added bonus, Etsy protects transactions between consumers and traders within the platform.

On this occasion, we would like to draw the attention of journalists who may also be reading this text: all our trading platforms offer the Souvenir Geiger counter product, which is a charity initiative aimed at supporting two areas at once:

– support for defense projects and the Armed Forces of Ukraine;

– clearing the DIY market of defective Soviet-era Geiger tubes.

The Etsy store is now fully operational. We invite you to visit following the link go.iot-devices.com.ua/etsy

About IoT-devices, LLC

The Ukrainian company IoT-devices, LLC has been operating in the DIY electronics market since 2020. The company’s flagship product is the Geiger counter module GGreg20_V3 with pulse output.

The company also has a number of other interesting products. For example, I2CUI4, a module for building user interfaces. I2CHUB, a splitter module for the I2C bus. ESP12.OLED, a universal controller module based on ESP8266. And other equally interesting electronic modules.

We try to design and develop modules so that they are compatible with as many popular IoT platforms as possible, such as ESPHome, Home Assistant, Arduino, NodeMCU, ESP-IDF, Tasmota, NodeRed, Raspberry Pi, etc.

The company’s products have already found their users in more than 20 countries, and we continue to develop the international business despite the aggressive war waged against our country.

Since 2021, the company’s products have been sold not only on the company’s website, but also through the Tindie platform, which is well-known among radio amateurs.

In 2023, we launched an Etsy store to expand our offer to users of this platform.

Easy Links

go.iot-devices.com.ua/shop

go.iot-devices.com.ua/etsy

go.iot-devices.com.ua/tindie

go.iot-devices.com.ua/github

go.iot-devices.com.ua/hackaday

go.iot-devices.com.ua/twitter

go.iot-devices.com.ua/facebook

go.iot-devices.com.ua/linkedin

go.iot-devices.com.ua/bluesky

Good luck!

IoT-devices, LLC Team

https://journals.kntu.kherson.ua/index.php/visnyk_kntu/article

Our modules were used in the project GGreg20_V3 and ESP12.OLED_V1

The article analyzes open data on radiation air pollution in the city Kyiv and visualized the data using analytical tools of the Python programming language.

When we developed GGreg20 in 2020, we did not know anything about these things at all. Now we can share our company’s experience with anyone who needs help or is just looking for more information

Please note that we are mostly comparing the SBM20 і J305 Geiger-Muller tubes, that the GGreg20_V3 comes with, and the LND712 tube is mentioned here as another alternative to both tubes. This allows us to extend the comparison to the capabilities of the more complex and expensive LND712 tube. Without such comparisons, this publication would have no depth and would be reduced to the thesis that SBM20 and J305 are interchangeable and therefore there is nothing to compare them.

Here are the key points to consider when choosing a Geiger-Muller tube for a DIY project:

• The purpose of the DIY project;
• Types of radiation that the tube can detect;
• Sensitivity of the tube;
• Internal noise and insensitivity;
• Operating voltage level;
• Dimensions and method of mounting the tube;
• Country of origin and year of manufacture.

Let’s consider and compare the tubes from these angles in more detail.

The purpose of the DIY project

The way you set the project goal may determine what success criteria you will use to measure the results you have or have not achieved.
With the Geiger counter, the project goal can also be very different.
For example:

• a cheap stationary device that should measure background radiation and alert you to danger most of the time;
• a miniature pocket device as a personal safety sensor for hiking;
• a sensitive and high-speed meter for detecting radiation in food and other materials;
• a meter/signalizer for radioactive gases in the air, such as household radon.

The task for which the end device is being developed may require the selection of a tube in terms of size and not require high sensitivity at all, etc. Therefore, only the user can determine for himself which tube in the Geiger counter is suitable. We can only point out that the selection of a tube according to the project task is a complex multifactorial analytical process, which we have tried to describe in depth in this publication.

Types of radiation

It is quite simple: you need to choose a tube depending on what radiation you need to measure in your project.
Most common tubes are sensitive to gamma and beta radiation. Some tubes are also capable of measuring the alpha channel.
Please note that the alpha channel in tubes is usually realized by having a mica window in the end of the housing.
To convert an a,b,g-tube to a b,g- tube, it is enough to close the mica window tightly with a piece of paper or the plastic cover of the housing.
To turn a b,g- or a,b,g- tube into a g- tube only, you need to shield the tube from beta particles. This can be accomplished by an aluminum casing with a thickness of several millimeters. Such an aluminum casing shields the tube from both beta and alpha particles at the same time.

As far as this article is concerned, the SBM20 and J305 tubes are capable of measuring beta and gamma radiation. The LND712 tube has all three channels: alpha, beta, and gamma.

How can this affect a DIY project from a practical point of view?

If you plan to measure only gamma rays with the SBM20 / J305 tube, then you need to shield such a tube from beta particles.
If you need to measure only beta particles with the SBM20/J305 tube, then you can try to use two such tubes at the same time: one with a shield that protects against beta particles, and the other without such a shield. In this case, by finding the difference between the measurement results for each tube, we can calculate the quantitative characteristic for beta particles.
The same applies to alpha particles: by filtering the alpha channel and subtracting the results between the tubes, we find the quantity for alpha particles.
With the LND712 tube, which is sensitive to a,b,g-, it is possible to implement a project to measure household radon, in particular Radon-222, since this isotope is the source of alpha particles.
It should be emphasized that for measurements with several tubes, you need to have several GGreg20_V3 modules. Each module is connected to a separate GPIO of the main controller, which in turn will be able to count pulses independently for each tube.

Tube sensitivity

When we first started to figure out which tubes to use for our GGreg20 Geiger counter project a few years ago, we experimented and sometimes mistakenly chose tubes that were capable of producing only a few pulses per hour at background radiation levels.

Of course, they would be impossible to use in a DIY Geiger counter project, which should be sensitive enough to measure background radiation most of the time.

So, when you are choosing which of the GGreg20_V3 options to order, don’t worry and know that we have already tested different tube models for you and have included in the options only those that really work with the GGreg20_V3.

J305 and SBM20 tubes, although they have some differences, work equally well with our product.

The LND712 tube, although not currently available as an option for the GGreg20_V3, also works very well with our Geiger counter module..

In general, the LND712 has a lot of interesting functions and features that can make a project with the GGreg20_V3 module even more interesting. Perhaps in the future we will offer this tube as an additional option as part of the Geiger counter module of our production.

In terms of sensitivity (pulses/mR), the LND712 tube is not much different from the SBM20, but given that it is more modern, we would prefer it

Own noise and insensitivity

Geiger tubes have two important characteristics that should be taken into account when comparing them.

Internal noise is the false-positive pulses generated by the tube in the absence of external radiation. When designing or calibrating a tube, the manufacturer places the test sample in a radiation-shielded laboratory environment and measures the number of false-positive pulses per unit time. Typically, the intrinsic noise of the tube is specified in the datasheet in pulses per second.

The SBM20 tube, compared to the J305 and LND712, has a significantly higher intrinsic noise value according to the datasheet. This means that the SBM20 tube will measure natural background radiation much worse than the J305 or LND712 tubes.

Insensitivity is the time during which the tube recovers from the previous avalanche-like disturbance and is unable to detect the next such event. This time is commonly referred to as the dead time of the tube and is measured in microseconds. In practice, as a consequence, the tube is not able to generate an output pulse during this period of time.

It is also worth noting that the dead time directly depends on the size of the tube. The longer the tube is, the longer this time is. Of course, the length is not the cause, but only a consequence of the general design of most tubes and their principle of operation.

If your project is aimed at measuring high levels of radiation, this property of the tube must be carefully considered, because the higher the radiation we measure, the more dense the events that the tube records will be. At a certain point, the limit will be reached beyond which insensitivity will begin, i.e., the density of events in time when the tube simply does not have time to recover to register them.

Due to its size, the LND712 tube (90 microseconds) is the leader in this indicator, which is half that of the SBM20 and J305 tubes (190 and 180 microseconds).

Note. Here we present the Dead Time for J305 based on the data from the Internet, since the datasheets from suppliers do not contain this data.

Sensitivity to UV. It is worth mentioning the sensitivity of glass-bodied tubes (such as J305) to the rays of ordinary sunlight, especially to the UV spectrum. Indeed, you can find videos of experiments with a UV flashlight and ordinary sunlight on the Internet. The tubes in those videos are just going crazy from these stimuli, which can be seen with the naked eye.

We also conducted a quick test. We were unable to reproduce the behavior of J305 shown in the video. It is possible that the tube that generates false-positive events in the video from the Internet has some physical or technological defects that cannot be identified without special equipment.

We sympathize with the owner of such a tube. And because of this, we decided to test random samples from a batch of our J305 tubes, which are supplied as an option to the GGreg20_V3 module. Although our J305 tubes did not show such an effect, we fully agree that sunlight can create additional noise in measurements. We recommend placing the J305 tubes in a light-tight enclosure if possible.

With the Geiger counter module GGreg20_V3, we offer (as an option) a protective cover printed on a 3D printer. Although this cover is not able to act as a full-fledged shield for the high-energy photon flux of sunlight, it will at least partially filter one of the sources of possible noise.

The level of operating voltage

When comparing the available tube options, keep in mind that different types of tubes may have individual supply voltage levels. This information is usually included in the datasheet for the tube.

In practice, it is also important to keep in mind that the Geiger counter module (and its settings!) on which the tube you choose will be installed is crucial.

The GGreg20_V3 module was designed to be able to provide the widest possible range of operating voltages. On the one hand, the GGreg20 supports 200 – 1200 V in the high-voltage part. On the other hand, the module can be powered in the range of 2.4 – 5.5 V. As far as we know, this is the widest range of supply voltage among similar modules.

Therefore, in terms of high-voltage supply voltage, the GGreg20_V3 module supports all the tubes we are reviewing and comparing: J305 (380V for the model with a glass tube), SBM20 (400V), LND712 (500V).

In practice, beyond the scope of this material, we advise you to always pay attention to whether the module that will work with the tube allows you to adjust the voltage required for the tube to work. Exceeding the supply voltage of the tube is guaranteed to damage it. If the voltage is too low, the tube will simply not work.

Dimensions and method of mounting the tube

The J305 and SBM20 tubes have similar dimensions and a convenient mounting method that does not require soldering. From the point of view of manufacturing microelectronics for IoT devices, they are medium in size compared to other Geiger tubes.

SBM20 and J305 can be called interchangeable, because they have a similar operating voltage level, the same terminals, and almost the same dimensions, which allows you to replace the tubes with each other if necessary, if you can set the appropriate conversion factors for CPM.

It is particularly convenient that on the board of a Geiger counter module such as the GGreg20_V3, the mounting supports both tubes. It is also useful that the Geiger tube can be quickly removed from the module or replaced. In the case of the SBM20/J305, this is as easy as changing the batteries in a flashlight.

The LND712 has about half the length, which makes it ideal for the size of the a,b,g-radiation sensor. But its output pins are made in such a way that it only needs to be soldered. Therefore, LND712, paired with a much higher price, is no longer as “convenient” as SBM20 or J0305.

Sometimes, in order to adjust the settings of the Geiger counter module, you need to be able to remove the tube – in the case of LND712, this will be impossible without soldering.

It’s also worth noting that in the case of building pocket devices, the length of the tube can be crucial. Let’s see: the thickness of the device will also be affected by the battery, buttons, and connectors, so the diameter of the Geiger tube is leveled by these other limitations and does not affect the dimensions of the device body. However, the length of the tube requires an increase in the size of the device body. For these reasons, the LND712 tube is significantly better than the SBM20/J305.

Country of origin and year of manufacture

In our opinion, the country of origin is no less important than the other characteristics of the tube. Even from a purely practical point of view (cost and time spent on logistics, supporting local businesses, paying taxes, etc.), it is better to buy a tube that is made in the United States.

Unfortunately, we are not aware of any opportunities to purchase tubes made in Ukraine. Our quick searches for Ukrainian tubes did not turn up anything..

If you know of any Ukrainian-made Geiger-Muller tubes, please contact us

The stocks of Soviet SBM20 tubes at private sellers are significantly depleted. The shelf life of the Soviet models has long since expired. That is why we are constantly looking for alternatives. One such alternative is the Chinese-made J305 tube. The J305 tubes sold on Alibaba and Aliexpress are of 2020-2022 production year and fully meet our requirements in terms of technical characteristics and quality.

LND712 tubes also have excellent specifications, quality, and functions. The only drawback is that they need to be purchased in the United States, with long logistics to Europe. Given the higher relative cost of these tubes and the lack of an organized official retail distribution network for LND712, it is clear why this tube has not been in the lead in the statistics of DIY Geiger counter projects.

Conclusions

We’ve been monitoring our own statistics for several years now, as well as those of projects like radmon.org, ThingSpeak, uRADMonitor, and others.

The Soviet-made SBM20 tube is probably the most popular among those used in DIY projects.

However, it is almost impossible to buy SBM20 anymore, as Soviet-era stocks are depleting, the shelf life and expiration date have expired, and the manufacturers of modern SBM20 tubes are only in a country that is under sanctions and is an internationally recognized aggressor, a sponsor of terrorism and is currently committing war crimes and crimes against humanity at least in Ukraine.

At the same time, the Chinese J305 is much easier to find and buy online, but only when it comes to the glass-body version. Unfortunately, J305 with a metal body is currently very difficult to buy for reasons unknown to us.

Unlike the SBM20 and J305, the American LND712 tube, in addition to beta and gamma, also has an alpha radiation measurement channel, which significantly expands its range of application in DIY projects. The LND712 tube has a metal body, like the SBM20, and a mica window for detecting alpha particles.

On Internet forums, users have suggested that the glass body of the J305 is not protected from photons of normal sunlight, which can interfere with the measurement process if the tube is not additionally protected by a sunproof cover.

We are not sure of this statement, although there is also some understanding on our part that glass tubes require a sunproof cover as glass can transmit light, including noise, which can increase the noise level of observations.

Conversely, the metal housing of the SBM20 and LND712 tubes can act as a shield to a small extent for electromagnetic interference and sunlight. This makes the measurement performance of metal tubes more stable. On the other hand, a tube with a glass body may be more sensitive to radiation, which is also a useful property under certain conditions.

But it should be noted that all of these are just assumptions that should be tested. However, we are not able to test all of this, because such tests require a specially equipped laboratory.

Besides, we always have a much better tool – the manufacturer’s datasheet. The tube must meet the characteristics and operate in the manner specified in the datasheet.

If we were choosing a tube for ourselves, we would not hesitate to choose the LND712. However, since GGreg20_V3 does not currently support this tube size, we would choose between SBM20 and J305 as follows:

• Shelf life – J305 is better;
• Internal noise – J305 is better;
• Sensitivity – J305 is better;
• Country of origin – J305 is better;
• Background radiation – J305 is better;
• Calibration source – J305 is better (most tubes are calibrated by Co-60);
• Dead time – no difference;
• Metal case – SBM20 is better;
• Dimensions and mounting – no difference;
• Supply voltage – no difference;
• Retail distribution network – J305 is better;
• Price and quality – J305 is better.

Guided by the data from the documentation, statistics from the Internet and our own experience, we would definitely choose the J305. We would choose SBM20 only in exceptional circumstances, when for some significant reason J305 would be impossible to use.

Thank you for your attention!
Team IoT-devices, LLC

Additional resources on the topic:

https://iot-devices.com.ua/en/ggreg20v3-geiger-tube-j305/
https://iot-devices.com.ua/en/technical_note_supply_voltage_range_geiger_counter_ggreg20_v3/
https://iot-devices.com.ua/en/uv-test-of-the-j305-geiger-tubes/
https://iot-devices.com.ua/en/technical_note_performance_of_diy_geiger_counter_ggreg20_v3_at_low_-temperatures/
https://iot-devices.com.ua/en/geiger-counter-emulator-ggreg20_v3-module-by-means-of-esp8266-part1/
https://iot-devices.com.ua/en/maximum-radiation-that-can-be-measured-by-geiger-counter-ggreg20_v3-en/
https://iot-devices.com.ua/en/ggreg20v3-case-3d-model-for-personal-use/

Easy Links:

go.iot-devices.com.ua

/geiger-counter
/high-voltage-converter
/geiger-counter-emulator
/tindie

There are a lot of publications on the Internet on how to convert CPM (Counts per Minute) obtained from a Geiger tube to radiation levels. However, despite the wide coverage of this topic on various forums and a wide range of examples with code for various programming languages, we had to understand the topic deeper than we wanted to in order to be able to properly calculate the conversion factor for Geiger tube SBM20 from CPM to absorbed dose of radiation μSv/h and configure the conversion in our own products and make an example calculation for everyone

IoT-devices, LLC is producing its Geiger counter module GGreg20_V3 with a pulse output and two types of tube to choose from. Currently, customers can choose either SBM20 or J305 when ordering a device from our production.

We plan to create separate documents for each of the popular tubes, and we are starting with a technical note on SBM20.

Therefore, in this document, we will look at the procedure for calculating the CPM to microsieverts per hour conversion factors for SBM20. For other common tubes, at least J305 and LND712, it will be covered later.

While collecting materials for this article, we came to the conclusion that this is not an easy task at all, because information is spreading on the Internet, which needs to be verified, and sometimes we even had to investigate where certain coefficients came from.

Let’s start with the useful information that manufacturers provide in their datasheets for their tubes.

Solution

Let’s make calculations for SBM20 based on the manufacturer’s data:

Count rate at 4 μR/s from a Cs-137 source of pulses per second: 240 – 280;

1. Let’s take the average of these two values:

This is the average count rate at 4 μR/s from a Cs-137 source of pulses per second.

(240 + 280)/2 = 260 CPS / μR/s

2. Convert to pulses per second at 1 μR/s: μР/с:

260 / 4 = 65 CPS / μR/s

3. Convert to pulses per second at 1 mR/s:

65 * 1000 = 65000 CPS / mR/s

4. Convert to pulses per second at 1 mR/h:

round( 65000 / 3600) = 18 CPS / mR/h

5. Convert to pulses per minute at 1 mR/h:

18 * 60 = 1080 CPM / mR/h

6. Convert to pulses per minute at 1 μSv/h:

1080 / 10 = 108 CPM / μSv/h

or

108 CPM = 1 μSv/h

or

1 CPM = 1/108μSv/h

7. Calculate the value of one pulse per minute:

1 / 108 = 0.00926

Thus, if we need to convert the pulses recorded by the SBM20 tube during a minute into μSv/hour:

This is the value of the equivalent radiation dose recorded by the sensor – the SBM20 tube.

Please note that we took the average value of CPS / μR/s = 260 and obtained the value of CPS / mR/h = 18 by simple mathematical transformations.

We can also perform the above calculations not only for the average, but also for the minimum and maximum values specified in the data sheet for the tube: 240 CPS and 280 CPS at 4 μR/s.

In this case, we will get two additional values that we can also work with if necessary.

For convenience, let’s write them in CPS at 1 mR/h:

min value: 17 CPS / mR/h
max value: 19 CPS / mR/h

Let us summarize the results of our work at this stage of the calculation:

Everything would have been fine, and we could have stopped calculations there. But the coefficient we calculated, 0.00926

0.00926

only allows us to obtain the exposure value recorded by the Geiger counter. We are primarily interested in the equivalent dose of radiation absorbed by the human body.

Therefore, let’s move on to the next part of the calculations.

Although we are not a research institute, to solve our simple task we will have to dive into complex matters for a while.

In order to estimate the equivalent dose of energy absorbed by the human body, science uses the so-called human body phantom model, which calculates certain conversion factors for converting one value to another.

If you are interested in reading the theory on this subject, we can advise you to read this publication:

https://web.archive.org/web/20230402162906/https://www.automess.de/en/service/radiation-quantities-and-units

And we proceed to derive the conversion factor of the tube CPM into the equivalent dose of absorbed radiation in microsieverts per hour, taking into account the phantom model of the human body.

Let’s start the calculation with the already found coefficient of 18 CPS per 1 mR/h. Why is this so? Next, you will see that most tube manufacturers (J305 and LND712 included) provide parameters in this format in the datasheet for their products.

For example,

• for the J305 is specified in the datasheet: sensitivity of γ (60Co) cps/ mR/h 44
• for LND712: GAMMA SENSITIVITY CO60 (CPS/mR/HR): 18

where CPS – Counts per Second; mR – milli roentgen; h = hr – hours.

In the case of the SBM20 tube, the manufacturer specifies data for the Cs-137 source.

And we have already made the necessary conversions in the previous step:

Sensitivity of SBM20 to gamma rays: 18 CPS / mR/h 1.

1. Convert CPS to CPM at 1 mR/h (we already have this value, but we are going to calculate it again for the reader’s convenience):

18 * 60 = 1080 CPM / mR/h

2. Convert CPM at 1 mR/h to CPM at 1 R/h:

1080 * 1000 = 1080000

3. Find the value of the exposure dose R/h per 1 CPM:

1 / 1080000 = 0.0000009259259259

4. Find the air kerma (Ka, kinetic energy released per unit mass / in matter):

The equation is as follows:

Ka [Gy] = 0.00877 [Gy/R] x exposure [R]

where 0.00877 is the coefficient of radiation dose absorption by the human body on the phantom model under the influence of photon energies of 100 keV – 3 MeV

Note. For more details, see the link: https://web.archive.org/web/20230402162906/https://www.automess.de/en/service/radiation-quantities-and-units

0.00877 * 0.0000009259259259 = 0.00000000812037037 Ka[Gy]

5. Convert Ka[Gy] to Ka[uSv] (i.e., switch from Gray to µSv):

0.00000000812037037 * 1000000 = 0.00812037037 Ka[uSv]

6. Perform the check and find the inverse value:

0.00812037037 ^(-1) = 123.1470924

Thus, the formula for the equivalent absorbed dose of radiation by the human body for the Geiger-Muller tube SBM20 with gamma sensitivity for Cs-137 of 18 CPS / mR/h is as follows:

where

0.00812 μSv/h is the value of one count, CPM;

CPM – number of counts per minute.

We can also calculate the coefficients for the minimum and maximum CPS / mR/h values provided by the datasheet:

At the same time, the Internet uses a coefficient of 175.43 (0.0057), which, as can be seen, does not fit into the calculations above. However, this coefficient is similar in value to the data for SBM20 for Ra-226 taken from the Internet:

In order for the CPM to uSv/h conversion factor to be 0.00570, the initial value of CPS/mR/h in the tube datasheet should be 25.643. We determined this by the simple value adjustment (25.643 * 60 / 8.77 = 175.4367; 1 / 175.4367 = 0.00570).

Another popular coefficient for the SBM20 tube is also published on the Internet: 150.5131 (0.00664), allegedly calibrated to Co-60. We do not know where this information came from.

Additional calculations

What else can we do to try to find the 0.0057 coefficient that is used everywhere for SBM20?

Switching from coefficients for Cs-137 to Co-60

We can try to move from the values at Cs-137 (which is indicated in the tube documentation) to Co60, which is now the most commonly used standard for calibrating Geiger-Muller tubes in the world.

To do this, it is necessary to calculate the conversion factor for Cs-137 to Co-60 values.

Let’s take the average value for the two Co-60 energy lines:

Co-60: 1.1732 MeV; 1.3325 MeV; Average value: 1.25285 MeV

And the energy value of Cs-137:

0.6617 MeV

Let’s find the energy ratio of Co-60 to Cs-137:

1.25285 / 0.6617 = 1.893380686

Next, we calculate the corresponding value of CPS at 1 mR/h:

18 * 1.893380686 = 34.08085235

Assuming that this value is indicated in the data sheet for the tube, we will calculate the new coefficient of the absorbed equivalent dose of μSv/h per 1 CPM for Co-60:

34 CPS / mR/h

1. Convert CPS to CPM at 1 mR/h:

34 * 60 = 2040 CPM / mR/h

2. Convert CPM at 1 mR/h to CPM at 1 R/h:

2040 * 1000 = 2040000

3. Find the value of the exposure dose R/h per 1 CPM:

1 / 2040000 = 0.0000004901960784

4. Find the air kerma (Ka, kinetic energy released per unit mass / in matter):

The equation is as follows (as in the previous calculation):

Ka [Gy] = 0.00877 [Gy/R] x exposure [R]

So:

0.00877 * 0.0000004901960784 = 0.000000004299019608 Ka[Gy]

5. Convert Ka[Gy] to Ka[uSv] (i.e., switch from Gray to µSv):

0.000000004299019608 * 1000000 = 0.004299019608 Ka[uSv]

uSv/h = CPM x 0.00429 for Cs-137->Co-60

Switching from coefficients for Cs-137 to Ra-226

We calculate the conversion factor from Cs-137 to Ra-226 in a similar way:

Because Ra-226 has several energy lines of gamma radiation:

186.2 keV;
240.3 keV;
295.2 keV;
352.0 keV;
609.3 keV;
657.0 keV;
768.4 keV;
934.8 keV.

we will select all of them that can be detected by the SBM20 tube. According to the documentation, the SBM20 is sensitive to gamma quanta from 0.05 MeV to 3 MeV.

Therefore, all of these lines fall within the detection range. In order to move from Cs-137, we need to either work with the average of these lines or select the line most characteristic of Ra-226.

If we need to rely on a specific line to identify a radionuclide, we need to take into account the intensity and energy of this line. Usually, the so-called “characteristic peak” is used to identify a radionuclide, which is the most intense and is located at the most characteristic energy for this radionuclide.

In the case of the gamma spectrum of Ra-226, which consists of several lines, the characteristic peak can be determined by the highest intensity and energy of the line. According to the table of line intensities of the Ra-226 gamma spectrum, the line with an energy of 609.3 keV is the most intense line, so this line can be used to identify Ra-226.

The average value of the energies of all lines of the gamma spectrum of Ra-226 can also be determined, but it is not useful for identifying the radionuclide. However, the average value is useful for determining the average gamma energy of a given radionuclide.

The table of line intensities and energies can be used to calculate the average gamma energy of Ra-226.

Let’s calculate the sum of the energies of all lines of the Ra-226 gamma spectrum:

0.186 MeV + 0.244 MeV + 0.295 MeV + 0.351 MeV + 0.609 MeV + 1.061 MeV + 1.158 MeV + 1.332 MeV = 5.196 MeV

Divide the sum of energies by the number of lines to get the average energy:

5.196 MeV / 8 = 0.6495 MeV

Thus, the average gamma energy of the Ra-226 radionuclide is approximately 0.65 MeV. Note that this value is only an average energy and may differ from the individual values of the gamma spectrum lines.

Now we have three alternative values that we can use to find the conversion ratio from Cs-137 to Ra-226 calibration. The third option is the weighted energy value provided on the hps.org website.

1. Characteristic peak: 609.3 keV [peak];

2. Average energy of gamma radiation: 0.6495 MeV [avg];

3. Weighted value of gamma radiation energy: 0.74 MeV [wght].

See. https://web.archive.org/web/20230404222401/https://hps.org/publicinformation/ate/q4817.html

Let’s calculate the corresponding energy ratios:

Cs-137 energy value: 0.6617 MeV.

Find the energy ratio of Ra-226 and Cs-137:

peak: 0.6617 / 0.6093 = 1.086000328245528
avg: 0.6617 / 0.6495 = 1.018783679753657
wght: 0.74 / 0.6617 = 1.118331570197975

Next, we will calculate the corresponding value of CPS at 1 mR/h, i.e., we will move from the Cs-137 calibration, as indicated in the datasheet, to the calculated calibration value relative to Ra-226:

peak: 18 * 1.086000328245528 = 19.5480059084195
avg: 18 * 1.018783679753657 = 18.33810623556582
wght: 18 * 1.118331570197975 = 20.12996826356355

As we can see, the attempt to switch from Cs-137 to Ra-226 did not give us anything either, because we could not get the target CPS value of 25.643/mR/h, at which it is possible to obtain a coefficient of 0.00570.

The coefficient of 0.00429, which we obtained earlier for the case of Cs-137->Co-60, is also not similar to the common one for SBM20 175.43 (0.0057). Therefore, we can only guess where the Internet contributors got it from and use the one we obtained above by calculations based on the information in the datasheet for the tube.

Note . If you thought that we did not check the datasheets of the modern production SBM20 and only rely on outdated Soviet data, this is not the case. We have checked all possible sources available on the Internet. SBM20 tubes produced in 2021 and later have different calibration options in their documentation:
– 78 imp/μR without specifying a source (1/150.5131129, or 0.006643);
– 105 imp / µR at Ra-226 (1 / 198.4036488, or 0.005040);
– 67.5 imp/μR at Cs-137 (1 / 129.9885975, or 0.007692);
None of the documents we studied contains source data that could lead us to the coefficient of 0.0057 μSv/h at 1 imp/min.

As a reminder, our recommended formula for the equivalent radiation dose absorbed by the human body for the Soviet Geiger-Muller SBM20 tube with a gamma sensitivity of 18 cps/mR/h for Cs-137 is as follows:

where

0.00812 μSv/h is the value of one count, CPM;
CPM – number of counts per minute.

Conclusions

In this article, we have provided a detailed step-by-step calculation of the conversion factor for the data transmitted by the Geiger counter with the SBM20 tube and figured out what factor we need to apply in order to not only get the level of exposure dose recorded by the sensor, but also the dose absorbed by the human body.

Unfortunately, we could not figure out where the magic coefficient of 0.0057 μSv/h per 1 CPM, which everyone uses, came from. Neither mathematical transformations, nor the transition from Cs-137 to Co-60, nor the transition from Cs-137 to Ra-226, nor the adjustment of the coefficient (in particular, 8.77, 0.94 to 0.98) of the absorption dose for the phantom model of the human body gave the desired results. It seems that this is a special case that someone, at some point, simply accepted their calculations and did not leave instructions for us.

Please write to us if you have your own version of where 0.0057 came from or a good calculation on this topic. We will be grateful and will make appropriate additions to this post.

At the same time, we were able to find a mathematically sound calculation of another magic coefficient

8.77,

which is used to obtain the value of the radiation dose absorbed by the human body. Now you also know where it comes from.

Currently, for soviet tubes, we recommend that instead of the coefficient of 0.0057, use the coefficient that we calculated for the equivalent dose of radiation absorbed by the human body:

where

0.00812 μSv/h is the value of one count (CPM) for the SBM20 tube calibrated against the Cs-137 source;
CPM – number of counts per minute.

If your SBM20 tube has a different sensitivity factor in the documentation, or if your tube is calibrated by the manufacturer against a different radioactive source, we recommend that you use the data for your tube.

In the next publications for J305 and LND712 tubes, there will be a little less text, because almost all coefficients published on the Internet correspond to our calculations.

And we have not yet covered the topic of internal background (false-positive) pulses for Geiger tubes. The work is not over yet!

Stay tuned!

Thank you for your attention!

Team IoT-devices, LLC

We wondered what would happen if we took our DIY Geiger counter module GGreg20_V3 and put it in a freezer with a target temperature of -23 Celsius together with the ESP32 controller.

Will our sensor work at such a low temperature? Will we see any failures or deviations in the radiation sensor measurements?

My colleagues and I were betting that sooner or later we would get False-Positive pulses at the ESP32 input during strong cooling.

The fact is that when it comes to such a modular system, it may contain several points of failure that can show up during operation at low temperatures. Before starting the test, we considered the following as possible points of failure:

• the Geiger counter module board,
• the ESP32 controller board,
• the connections between them,
• and the Geiger-Muller tube SBM20.

Each of these components could stop working or become unstable due to deformation of materials, changes in the conductivity of wires and contacts, or the formation of dew or ice on the surface of the electronics.

Although the Geiger-Muller tube has an appropriate temperature rating (-60°C to +70°C) from the manufacturer, it can also change its behavior when exposed to low temperatures. For example, loss of pulse generation capability due to slowing down of molecular/electronic processes due to a decrease in the energy of particles in the gases filling the tube, or, conversely, avalanche-like ionization inside the flask due to the thermodynamic characteristics of these gases (Ne+Br2+Ar).

For this reason, it was interesting and important to conduct such a test of the GGreg20_V3 module and the circuit with the ESP32 controller that they create in DIY projects to answer potential questions from our users and customers who plan to use the GGreg20_V3 Geiger counter in harsh weather conditions.

We kept the sensor at such low temperatures for several hours. At the same time, we recorded measurements from the sensor by the Home Assistant server wirelessly and observed the measurement graphs.

And…. And we are satisfied with this test, but let’s not get ahead of ourselves and tell you how everything happened step by step.

So, in this experiment, we aimed to investigate the performance of a DIY Geiger counter module at low temperatures. We placed the Geiger counter module and ESP32 controller in a freezer with a temperature of -23 Celsius and kept it there for 5 hours. We recorded measurements from the sensor and observed the measurement graphs to evaluate any failures or deviations in the radiation sensor measurements.

We were also able to measure the temperature of the sensor during the test because we had a temperature probe on hand (1-wire DS18b20 12-bit). However, we also monitored the external temperature of the module box several times during the test using a non-contact infrared thermometer

Results

We did not notice any failure or deviation in the radiation sensor measurements during the entire test period. The measurements from the sensor remained within the normal background radiation during the entire test period.

We also used these practical tests to check how the system would behave during the transition from warmth to deep cold, as well as from the cold of the freezer to normal room conditions, and found that there were no problems that could be detected by simple monitoring tools. The absolute value of the temperature drop (sharp decrease and increase) during the test was more than forty degrees.

Discussion

Our results suggest that the GGreg20_V3 radiation sensor is capable of performing reliably at low temperatures. This is an important finding as it implies that the sensor can be used in low-temperature environments without any significant loss of accuracy or reliability.

However, it is worth noting that our experiment was limited in scope, and further tests may be required to confirm the findings.

In particular, we did not do any statistical verification of the obtained data, but only conducted several long-term (up to six hours long) experiments and practically checked whether the sensor and the microcontroller would work normally.

Conclusions

In conclusion, our experiment showed that the GGreg20_V3 radiation sensor can perform reliably at low temperatures. We did not observe any failures or deviations in the radiation sensor measurements during the entire test period, indicating that the sensor can be used in low-temperature environments without any significant loss of accuracy or reliability. However, further tests may be required to confirm these findings and evaluate the performance of the sensor over an extended period.

Now you also know what happens if the Geiger counter GGreg20_V3 is placed in a low temperature environment.

We hope that you found this post as interesting and useful as the experiment we conducted.