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2182a overflow mV in autorange mode

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claudeahyi
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2182a overflow mV in autorange mode

Post by claudeahyi » March 1st, 2012, 10:37 am

Using the 2182a in autorange mode, it some times displays "overflow mV". Which I understand as "overflow in mV range". Since the 2182 is in autoranging mode why isn't it changing the range?
Note that I only saw that happening when the 7065 hall card was in High impedance mode. However that may not be of significance since voltages may be higher thanks to the high impedance.
Claude

Dale C
Keithley Applications
Keithley Applications
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Re: 2182a overflow mV in autorange mode

Post by Dale C » March 1st, 2012, 12:31 pm

I agree that it might be a high impedance effect.
The Model 2182A has a 10G input impedance.
The Model 7065 high impedance mode could be much higher >100T ohm (1e14).
So the 2182A could be looking at on open circuit. This charging the input.
it means nothing until the load is applied with a lower input resistance.And a good measurement can be made.
You are correct.
Overflow means the input signals has exceeded the range.

claudeahyi
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Joined: January 25th, 2012, 2:56 pm
Country: United States

Re: 2182a overflow mV in autorange mode

Post by claudeahyi » March 1st, 2012, 3:13 pm

Ok, but why is the 2182 not going from mV range to V range since it is in auto range mode ?

Dale C
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Re: 2182a overflow mV in autorange mode

Post by Dale C » March 2nd, 2012, 5:59 am

If the Model 2182A is in the Autorange mode and it is not autoranging then it requires service.
Can you apply a know voltage directly to the input of the Model 2182A and see if it autoranges?
If it does then something else is going on with the 7065 card or the general configuration.
If not, then it requires service.

claudeahyi
Posts: 5
Joined: January 25th, 2012, 2:56 pm
Country: United States

Re: 2182a overflow mV in autorange mode

Post by claudeahyi » March 2nd, 2012, 2:36 pm

The 2182 will autorange normally in part of the measurement. But then in the final part of the hall measurement the hall voltage alternates between -15mV and +5 mV (as measured in low impedance mode). Every time it should measure the higher voltage it shows "overflow mV". Note that in high impedance mode the voltage might be higher than 15mV. I am wondering if it could be that the nanovoltmeter doesn't have the time to switch ranges before the computer ask for data.
Claude

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