GQ Electronics Technical Support Forum

GQ Electronics Technical Support Forum
Home | Profile | Register | Active Topics | Members | Search | FAQ
Save Password
Forgot your Password?

 All Forums
 GQ Electronics Forums
 2.GQ Geiger Muller Counter
 Measuring Tube Voltage
 New Topic  Reply to Topic
 Printer Friendly
Author Previous Topic Topic Next Topic  


1189 Posts

Posted - 05/13/2013 :  20:36:23  Show Profile  Reply with Quote
There are two ways to measure the voltage on GMC-080, GMC-200, GMC-280, GMC-300, GMC-320 tube:

1. Use a 10M ohm mutimeter 1000V range to check the voltage on tube two ends. For 380-450V, the meter should read about 180V.

2. To get better accuracy voltage reading, use following way. This is a generic method and it should work on most high voltage citcuit:

You need a regular 10M ohm internal resistance multimeter. Serial a 1G ohm resistor on your multimeter prob. Read the voltage frm the multimeter with 20V range.

And then calculate the actual voltage by following formular:

V(actual) = V(DMM read) x ((R(meter ohm) + R(probe ohm)) / R(meter ohm))

Voltage = V(reading from multimeter) * 91.9

if your multimeter reading is 4.2V, then the actual voltage is 4.2*91.1 = 382.62V
Reply #1


39 Posts

Posted - 10/10/2013 :  15:21:18  Show Profile  Reply with Quote
When it says check the voltage on the tube ends, is that installed, powered up and for a required tube voltage of 380-450, you should measure around 180V? I have a 4011 tube from here, voltage range for this tube ? so I should be setting it too ?
Go to Top of Page
Reply #2


1189 Posts

Posted - 10/20/2013 :  21:02:57  Show Profile  Reply with Quote
To get accurate voltage, use above formular to calculate.

The 140V-150V is measured directly by a regular 11M digital multimeter on a 1000V range position.
Go to Top of Page
Reply #3


20 Posts

Posted - 10/28/2013 :  21:40:44  Show Profile  Reply with Quote
* I don't know about the M4011, but some G-M tubes are very touchy about added external capacitance. Legend has it that the capacitance between your meter's test leads (as much as 20pf) can take out some G-M tubes. _That_ is the reason for the "minimum anode resistor" specification (frequently: 4.7 meg-ohms), since any capacitance on the other side of that won't hurt the tube.

Consequently, the suggestion here to measure anode voltage through a stand-off resistor at the end of your meter's probe is excellent advice.

If you have a 100 meg-ohm resistor (or make one out of 10 10M resistors), keep it clean and calculate what's on the anode side of that resistor per the ratio: meter resistance + 100M divided by the meter resistance. Example{ 10M + 100M / 10M = multiply display by 11x.

For better accuracy, add another 4% to the example --due to the 110M load against the 4.7M circuit board anode resistor (if that's what it is, and assuming you're touching down on the G-M anode).
Go to Top of Page
Reply #4


15 Posts

Posted - 05/16/2014 :  07:54:34  Show Profile  Reply with Quote
Do I have to remove the tube for the exact method?
Regards, Benedikt
Go to Top of Page
Reply #5


1189 Posts

Posted - 05/20/2014 :  15:39:08  Show Profile  Reply with Quote
No. The tube has much higher resistance. You do not have to remove it.
Go to Top of Page
Reply #6


4 Posts

Posted - 11/10/2015 :  09:53:45  Show Profile  Reply with Quote
Craig; is it that the tubes are "touchy" about capacitance or is it the loading on the DC-DC converter that drops the voltage ?

In either case ZLM's method should work fine (1G series)as long as the
resistor doesn't have too much parasitic capacitance. Some HV resistors with the single serpentine type element can be 5-10pF.

You can decrease the effective cap by several R's in series but hard to find higher than 20M in the smaller resistors.
Go to Top of Page
Reply #7


40 Posts

Posted - 03/08/2016 :  00:03:22  Show Profile  Reply with Quote
Can I use a oscilloscope with a 10:1 probe? E.g. DSO nano?
Go to Top of Page
Reply #8


10 Posts

Posted - 05/01/2016 :  21:56:44  Show Profile  Reply with Quote
Nudnik Posted - 03/08/2016 : 00:03:22 Can I use a oscilloscope with a 10:1 probe? E.g. DSO nano?

a 100x probe would probably be safest to check voltages at the tube.
Go to Top of Page
Reply #9


1 Posts

Posted - 05/23/2018 :  12:24:56  Show Profile  Reply with Quote
Hi, your method ZLM to measure high voltage with very low currents is very interesting, my question is, what multimeter has an impedance of 11 megaohm, mine have 10 megaohm.
thanks and regards
Go to Top of Page
Reply #10


1189 Posts

Posted - 08/12/2018 :  10:07:46  Show Profile  Reply with Quote
It should be 10 Megaohm.
Go to Top of Page
Reply #11


1 Posts

Posted - 08/25/2018 :  05:29:38  Show Profile  Reply with Quote
hey there
thank you now i khnow how to meausre voltage

Edited by - Ezra on 10/01/2018 06:38:16
Go to Top of Page
  Previous Topic Topic Next Topic  
 New Topic  Reply to Topic
 Printer Friendly
Jump To:
GQ Electronics Technical Support Forum © Copyright since 2011 Go To Top Of Page
Generated in 0.09 sec. Snitz Forums 2000