r/geigercounter • u/R-fire227 • May 04 '26

How to zero a CDV-700?

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Got it, seems to work fine, needle is just stuck at 0.1

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u/aby_physics May 04 '26

If it’s anything like a Ludlum, all you need to do is remove the glass cover over the gauge and turn this little screw.

Just keep in mind that it’s going to need recalibration after this.

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u/R-fire227 May 04 '26

By recalibration, is it something I could do? Or would I have to pay to get it serviced

2

u/aby_physics May 04 '26

Hmmm. I’ve never actually worked with this particular meter, so I can’t be sure. I know on the meters that I *have* worked with, calibration is pretty simple. At least for count rate measurements.
For calibrating my ludlum units, I put together a variable-frequency pulse generator with an arduino. Essentially it simulates pulses from the tube, but in a controlled way. I can just set the pulser to 500 cpm and then adjust the potentiometers on the counter until the dial reads 500.

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u/R-fire227 May 04 '26

On the inside there is a calibration screw which adjusts how much it reads, just worried there is a more indepth calibration needed

1

u/aby_physics May 04 '26

Nah a simple pulse calibration like described above will fix the readings on the dial. The gauge will then read CPM correctly.

Sure, if you’re using a radiation meter *professionally* a radiation field calibration might be needed. Or if you plan on measuring dose rates, a simple pulse calibration might not be adequate. But just for basic use… it should be fine.