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 2.GQ Geiger Muller Counter
 Too high values with 320+V5

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malezet Posted - 02/28/2022 : 15:00:24
I have problem with device 320+V5 Revision 5.20
Measured values are too high, about 4-5uSv/h, should be 0.2uSv/h max

I performed factory reset, cleaned inside and tube from little dust.

Regards
Zygmunt
29   L A T E S T    R E P L I E S    (Newest First)
Damien68 Posted - 03/11/2022 : 01:25:46
if you have time what you can try is to make a closed loop with a coper conductive wire to encircle L1 which should lower the quality factor of the inductor and therefore the output voltage.
I have not tested the solution, it is only theoretical.

ullix Posted - 03/11/2022 : 00:58:45
quote:
Originally posted by EmfDev

Maybe replacing the high voltage parts will fix the issue.

@EmfDev: With all due respect, but are you really suggesting that the user should resolder a SMD based circuit board to fix a construction deficit, which GQ has created?

quote:
In history of my counter there was a time (~3 years ago), when radiation level was very high for over 3 days - nuclear medicine (from 500uS/h to the 5 or 8 after 3 days). For last 3 years, counter was online almost 2.5 years. Normal radiaton in my place is about 0.2uS/h.
Is that "Normal radiation" from any official institution which measured on a place near you, or from what your own counter was reading? What is/was your counter's "normal" reading in CPM?

The period with high radiation levels will not have had any effect on the HV of the counter.

I thought you had a new device, but it is already >3 years old. I wonder whether this very high voltage thing happened suddenly, or perhaps was present from the very beginning. It may not have been noticed initially, but now that the tube is burned out, it surfaces?

Do you, by any chance, have history downloads from the beginning up to now? I would like to review them, in particular apply the Poisson test. I kind of suspect they will fail.

If you have, please zip them and attach them to a discussion post on my GeigerLog site https://sourceforge.net/projects/geigerlog/
EmfDev Posted - 03/10/2022 : 17:01:03
Looks like your version actually does not have the potentiometer adjuster in the pcb and is based on PWM. Maybe replacing the high voltage parts will fix the issue.
malezet Posted - 03/10/2022 : 13:05:27
quote:
Originally posted by Damien68

quote:
Originally posted by malezet
"malezet, there must be people at your place in poland,"
What do you mean?


it is in reference to the bad news in ukraine and the number of refugees.


about 1.3mln now
Damien68 Posted - 03/10/2022 : 07:56:29
quote:
Originally posted by malezet
"malezet, there must be people at your place in poland,"
What do you mean?


it is in reference to the bad news in ukraine and the number of refugees.
malezet Posted - 03/10/2022 : 07:42:36
quote:
Originally posted by Damien68

malezet, there must be people at your place in poland,
let's hope best days for future.



"malezet, there must be people at your place in poland,"

What do you mean?
What should I do now? I see 4011 tubes on aliexpress. The price is 1/4 of original price of counter - acceptable.

In history of my counter there was a time (~3 years ago), when radiation level was very high for over 3 days - nuclear medicine (from 500uS/h to the 5 or 8 after 3 days). For last 3 years, counter was online almost 2.5 years. Normal radiaton in my place is about 0.2uS/h.

Regards
Damien68 Posted - 03/10/2022 : 07:08:05
malezet, there must be people at your place in poland,
let's hope best days for future.
Damien68 Posted - 03/10/2022 : 06:25:14
ullix, in this case the voltage adjustment is certainly in the software but not accessible to the user. or else maybe it can't be adjusted if this is no a PWM output but the electrical design of the 400v generator is the same as on my GMC-500+ except that there is no return with a 1Gohm resistor. which still makes a difference (it make a minimum load).
ullix Posted - 03/10/2022 : 06:15:39
quote:
Only multimeter with 10Mohm internal resistance: 302V
470Mohm and multimeter: 13.8V
2 * 470Mohm and multimeter: 6.7V
(470 + 10) / 10 * 13.8 V = 662 V
(470 + 470 +10) / 10 * 6.7 V = 637 V

Oh yes, way too much HV!

While the true characteristic of the M4011 tube is unknown, it is more than likely that you are well into the "continuous discharge" range of the tube, to which I referred in Reply#18. Which means the tube fires constantly like a fluorescent lamp (https://en.wikipedia.org/wiki/Fluorescent_lamp) without the need for a trigger from gamma or beta quanta.

Chances are the tube is already burnt-out, aka permanently damaged. The tube could be replaced, but as long as there is no provision to adjust the HV, the only option is to replace the whole counter.

This made me look again at my own GMC-300E+. There is definitely no menu entry which allows setting the voltage. And I again inspected the circuit board using a magnifier: there is no potentiometer or anything else which would allow turning.

At least not on the tube side. Don't tell me it exists on the bottom side, where you can't get to until you take everything apart?
Damien68 Posted - 03/10/2022 : 05:54:47
Hi malezet,
yes this is high 662v/636v.
in the calculation below R1 is the added external resistor (470 or 2x470 Mohms)
R2 is the internal resistance of your multimeter (10 Mohms)

we should expect that the voltage calculated with 2x470M is higher than that calculated with 1x470M, is not the case, there may be an additional instability but the orders of magnitude (minimized) are there.
malezet Posted - 03/10/2022 : 04:51:57
quote:
Originally posted by malezet

quote:
Originally posted by ullix

quote:
OK, but I don't see any voltage regulator.

Bummer. Neither do I. Not on your picture, not on my 300E+. There is one on the 500.

Looks like "feature" :-(

It would still be interesting to see a readout of your voltages by DVM!



I'm trying to get 1Gohm resistor.



Hi Friends!




Only multimeter with 10Mohm internal resistance: 302V
470Mohm and multimeter: 13.8V
2 * 470Mohm and multimeter: 6.7V

Voltage of tube should be 400V
In this case, current with 470Mohm and DVM in series should be 0.833uA and voltage on multimeter 8.33V but is 13.8V
With 2 * 470Mohm and DVM in series current should be 0.42uA and voltage on multimeter 4.21V but is 6.7V

Voltage on tube is higher than expected, so that means counter have broken HV part.
Please help.
ullix Posted - 03/04/2022 : 07:55:36
omigosh, I had not noticed he had already measured 300V with a 10Mohm DVM! Yes, this keeps the counts coming; CPM=881 - come on, you can do more!

That counter is probably beyond the plateau phase into the "Continuous discharge" phase as seen in this Wiki graph: https://en.wikipedia.org/wiki/Geiger%E2%80%93M%C3%BCller_tube


Let's see the positive side: he can use the counter as a fluorescent lamp flashlight.

Seattle, we have a problem!
Damien68 Posted - 03/04/2022 : 07:22:14
maybe you have a potentiometer on your revision, otherwise it should be set to a default value.
if malezet measure 300v with a multimeter/10Mohms there must be a problem.
the output voltage of this type of generator is directly a function of the effective Q factor of the inductance (including the parasitic capacitances of the diode and the transistor),
if one of the components has been changed by an equivalent, it cannot work without revise the PWM setting. several users including this dear Breizh seem to have problem with recurring spikes.
If that's the problem, it will require a firmware update.
ullix Posted - 03/04/2022 : 06:51:49
just checked all menu entries of my GMC-300E+ and have nothing found on voltage change?
Damien68 Posted - 03/04/2022 : 06:36:36
I have already seen photos of older versions of GMC counter with a potentiometer to adjust the 400v voltage.
on new revisions it has been replaced by a PWM output managed by the CPU and the 400v voltage must therefore be adjustable by the software.
malezet Posted - 03/04/2022 : 06:06:27
quote:
Originally posted by ullix

quote:
OK, but I don't see any voltage regulator.

Bummer. Neither do I. Not on your picture, not on my 300E+. There is one on the 500.

Looks like "feature" :-(

It would still be interesting to see a readout of your voltages by DVM!



I'm trying to get 1Gohm resistor.
ullix Posted - 03/04/2022 : 04:41:17
quote:
OK, but I don't see any voltage regulator.

Bummer. Neither do I. Not on your picture, not on my 300E+. There is one on the 500.

Looks like "feature" :-(

It would still be interesting to see a readout of your voltages by DVM!
malezet Posted - 03/04/2022 : 04:16:22
quote:
Originally posted by ullix

quote:
Now is CPM:881
:-) Strange.

I measured the anode voltage on my GMC-300E+ with two different 10 MOhm DVM, both of good quality. One gave 168 Volt, the other 160 Volt.

I see this as of little help to adjust the anode voltage. If you don't already understand the issue of internal resistance see my article "GeigerLog-Radiation-v1.1(CAJOE)-Support" from here: https://sourceforge.net/projects/geigerlog/files/Articles/ where this is discussed in chapter "Anode Voltage".

You need a resistor of at least 1 Giga-Ohm in series with the DVM. Doing that with my 2 DVMs, I now get 404 Volt and 403 Volt. The counter works well.

This also is more of a relative value, because, while the 1GOhm resistor is 1%, I have no idea how precise the "10 MOhm" of the DVMs is. The difference in the first values near 160 V suggest, they are also different.

But anyway, put together the highest resistance you have - and if you have none, use the DVM by itself - and give it a try. If the voltage is wayyyy off, you will know.


By the way: don't bother with the uSv. There is just a constant factor between the two: 881/5.73 = 153.75. This is the "Sensitivity" of the tube as laid down in the firmware = 154 CPM / (uSv/h), or as "Calibration" = 1/Sensitivity = 0.0065 uSv/h/CPM.



OK, but I don't see any voltage regulator.
ullix Posted - 03/04/2022 : 00:33:36
quote:
Now is CPM:881
:-) Strange.

I measured the anode voltage on my GMC-300E+ with two different 10 MOhm DVM, both of good quality. One gave 168 Volt, the other 160 Volt.

I see this as of little help to adjust the anode voltage. If you don't already understand the issue of internal resistance see my article "GeigerLog-Radiation-v1.1(CAJOE)-Support" from here: https://sourceforge.net/projects/geigerlog/files/Articles/ where this is discussed in chapter "Anode Voltage".

You need a resistor of at least 1 Giga-Ohm in series with the DVM. Doing that with my 2 DVMs, I now get 404 Volt and 403 Volt. The counter works well.

This also is more of a relative value, because, while the 1GOhm resistor is 1%, I have no idea how precise the "10 MOhm" of the DVMs is. The difference in the first values near 160 V suggest, they are also different.

But anyway, put together the highest resistance you have - and if you have none, use the DVM by itself - and give it a try. If the voltage is wayyyy off, you will know.


By the way: don't bother with the uSv. There is just a constant factor between the two: 881/5.73 = 153.75. This is the "Sensitivity" of the tube as laid down in the firmware = 154 CPM / (uSv/h), or as "Calibration" = 1/Sensitivity = 0.0065 uSv/h/CPM.
malezet Posted - 03/03/2022 : 13:54:57
quote:
Originally posted by malezet

quote:
Originally posted by malezet

quote:
Originally posted by malezet

quote:
Originally posted by malezet

quote:
Originally posted by EmfDev

Hi Zygmunt, can you please check what is the CPM? If you already did a factory reset then it maybe tube issue or the voltage is too high.



From writing a post, my meter was turned off to this day. Today, it indicates normal values.



Now (~5h later) values are higher. Counter is in one place, not moving.
CPM:142, 0.92uSv/h




Now is CPM:375, 2.44uSv/h and growing.




Now is CPM:484, 3.15uSv/h



Now is CPM:881, 5.73uSv/h
malezet Posted - 03/03/2022 : 13:35:18
quote:
Originally posted by EmfDev

The voltage between the terminals of the tube. The normal voltage should be around ~380-400V. But for 10Mohm multimeter, the reading should be around ~170V.



300V

I don't see any voltage regulator.
EmfDev Posted - 03/03/2022 : 11:26:34
The voltage between the terminals of the tube. The normal voltage should be around ~380-400V. But for 10Mohm multimeter, the reading should be around ~170V.
malezet Posted - 03/03/2022 : 04:34:43
quote:
Originally posted by malezet

quote:
Originally posted by malezet

quote:
Originally posted by malezet

quote:
Originally posted by EmfDev

Hi Zygmunt, can you please check what is the CPM? If you already did a factory reset then it maybe tube issue or the voltage is too high.



From writing a post, my meter was turned off to this day. Today, it indicates normal values.



Now (~5h later) values are higher. Counter is in one place, not moving.
CPM:142, 0.92uSv/h




Now is CPM:375, 2.44uSv/h and growing.




Now is CPM:484, 3.15uSv/h
malezet Posted - 03/03/2022 : 01:07:43
quote:
Originally posted by EmfDev

Hi malezet, how old is your device? It seems there might be a tube issue. Are you able to check the voltage between the tube terminals? Your version can adjust the voltage by twisting a screw in the middle of the board.



Date of purchase 2018-12-04.
Which voltage should be? I have multimeter with 10Mohm internal resistance.
malezet Posted - 03/03/2022 : 00:58:54
quote:
Originally posted by malezet

quote:
Originally posted by malezet

quote:
Originally posted by EmfDev

Hi Zygmunt, can you please check what is the CPM? If you already did a factory reset then it maybe tube issue or the voltage is too high.



From writing a post, my meter was turned off to this day. Today, it indicates normal values.



Now (~5h later) values are higher. Counter is in one place, not moving.
CPM:142, 0.92uSv/h




Now is CPM:375, 2.44uSv/h and growing.
EmfDev Posted - 03/02/2022 : 10:38:37
Hi malezet, how old is your device? It seems there might be a tube issue. Are you able to check the voltage between the tube terminals? Your version can adjust the voltage by twisting a screw in the middle of the board.
malezet Posted - 03/02/2022 : 10:26:32
quote:
Originally posted by malezet

quote:
Originally posted by EmfDev

Hi Zygmunt, can you please check what is the CPM? If you already did a factory reset then it maybe tube issue or the voltage is too high.



From writing a post, my meter was turned off to this day. Today, it indicates normal values.



Now (~5h later) values are higher. Counter is in one place, not moving.
CPM:142, 0.92uSv/h
malezet Posted - 03/02/2022 : 05:43:47
quote:
Originally posted by EmfDev

Hi Zygmunt, can you please check what is the CPM? If you already did a factory reset then it maybe tube issue or the voltage is too high.



From writing a post, my meter was turned off to this day. Today, it indicates normal values (0.15uSv/h).
EmfDev Posted - 03/01/2022 : 18:12:50
Hi Zygmunt, can you please check what is the CPM? If you already did a factory reset then it maybe tube issue or the voltage is too high.

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