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Error when using more than one Ch i ADC-20

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Error when using more than one Ch i ADC-20

Postby nille » Wed May 11, 2011 12:28 pm

I have a PICO ADC-20 Data Logger and I have a problem with a strange behavier.
I have a mV source with 1000,0 mV output.
When I have only Channel 1 activated on the 2.5 V range and my mV source connected to Ch1 my readings in PicoLog Recorder are 1000,44 mV but if I also activates Ch2 on the 2.5 V range so I have Ch1 and Ch2 activated my readings are 997,40 mV on Ch1. I does not matter if I have anything connected to Ch2 or not, the reading drops 3 mV anyway.
This only happends on the 2.5 V range, not on the 1.25 V range.
nille
 

Re: Error when using more than one Ch i ADC-20

Postby ziko » Tue May 17, 2011 3:20 pm

How are you physically connecting the inputs to the ADC20, what are you measuring exactly?

Kind regards
Ziko

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Re: Error when using more than one Ch i ADC-20

Postby nille » Wed May 25, 2011 3:09 pm

My input is connected in screw terminal 1 and screw terminal AG on a ADC20/ADC24 Terminal Board.
If I have two inputs I connect them to screw terminals 1+AG and 2+AG.
My mV source is a Eurotron MicroCal Calibrator.
nille
 

Re: Error when using more than one Ch i ADC-20

Postby ziko » Wed Jun 01, 2011 3:06 pm

Hi usually if the voltages are not reading correctly is when the common mode voltage of the device is exceeded. Depending on the voltage ranges this will be +/-1.9V or +/-3.0 V (CHannel to Common mode).

Or +/-30V Common to earth ground.

Can you send an image of the wiring?
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