| T O P I C R E V I E W |
| Bobakman |
Posted - 02/10/2023 : 18:56:49
Please view the linked videos.
I Noticed while measuring at a high count rate above 160K with the speaker enabled that the audio eventually drops out. One video I had the tube voltage set to 505V the second set to 530V to see if things differed and they did the audio drops out a bit sooner at the lower voltage and at a slightly lower count rate compared to the slightly higher setting.
My question then, is the audio dropping out (it tapers down to zero audio by the sound) due to loss of power due to the tube consuming more voltage and current from the extreme avalanche causing a lower voltage to be available to the audio power circuit? Or is the loss of audio by design since 160K clicks is basically a constant tone beyond the capability of the audio circuitry?
Bob
[https://youtube.com/shorts/yWoW77uvRGM?feature=share]
[https://youtube.com/shorts/NJLNZcTHZaQ?feature=share] |
| 8 L A T E S T R E P L I E S (Newest First) |
| ullix |
Posted - 02/15/2023 : 23:18:02
It is a bit hilarious when you realize that at CPM=160k, equalt o CPS=2600 you reach the point when a deadtime correction begins to become relevant.
But at this point the anode voltage collapses, and makes the need for any deadtime correction superfluous ;-)
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| Damien68 |
Posted - 02/15/2023 : 09:24:47
on the video after placing the counter on the source, we see the voltage of the HV generator drop from 500v to 385v then gradually rise from 385v to 398v (54 to 70%), this may explain the delay. in fact at the start of strong exposure the tube must be under powered (385v) and does not detect all the particles that he should so the count is still low enough to have the audio. after, the voltage increases and we obtain a pulse rate too high for the R3/C7 filter which cuts the audio.
R3/C7 filter enlarge by (220kohms*1nF= 220uS) the tube's detection pulse which is already 140uS which makes a "pulse width" of 140uS + 220uS = 360uS.
On the video the audio switch off at 150 000 CPM = 2500 CPS
1/(2500 CPS) = 400uS which is consistent with this theory. but this should only affect the audio and the loss of the audio path should not disturb the counts made by the microcontroller.
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| ullix |
Posted - 02/14/2023 : 00:40:52
This is very likely due to a collapsing of the anode voltage, because the High-Voltage generator is not powerful enough to support this high load on the tube.
Such things had been discussed already many years ago. Look at this forum topic:
http://www.gqelectronicsllc.com/forum/topic.asp?TOPIC_ID=5369
Relevant parts start at reply #15
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| Bobakman |
Posted - 02/13/2023 : 14:39:10
Thanks EmfDev for confirming. :>)
Bob |
| EmfDev |
Posted - 02/13/2023 : 13:43:40
It may be due to the high frequency on count that the speaker cannot handle. For the CPM difference, I saw on the first video that there was a delay on when you put the 600+ to the source, that may have cause the effect that it was slower than another. |
| ihab17 |
Posted - 02/11/2023 : 14:17:17
quote:
Originally posted by Bobakman
A 30+ year old CS-137 10 uci check source.
I pretty much figured as you stated but it never hurts to ask.
Bob
Wow! 30+? Go figure 30+ years ago! It was even double the count rate! |
| Bobakman |
Posted - 02/11/2023 : 11:00:41
A 30+ year old CS-137 10 uci check source.
I pretty much figured as you stated but it never hurts to ask.
Bob |
| ihab17 |
Posted - 02/11/2023 : 09:24:37
quote:
Originally posted by Bobakman
Bob
[https://youtube.com/shorts/yWoW77uvRGM?feature=share]
[https://youtube.com/shorts/NJLNZcTHZaQ?feature=share]
Interesting videos. I don't think any of the commercial counters, be it GMC or others, are designed to handle or measure such high radiation count rate. What was the source of your radiation? |
