keithley 487 autorange problem

[ömer]

Hi

I'm using keithley 487 pico ammeter voltage source in laboratory. 

When I measure current in autorange, I can't get a good measurement.

When the data goes to smaller range (nano ampere), when the scale change nanoscale

Measurement jump down and a sharp drop was seen in the Graf. 

[crossrulz]

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@ömer wrote:

Hi

I'm using keithley 487 pico ammeter voltage source in laboratory. 

When I measure current in autorange, I can't get a good measurement.

When the data goes to smaller range (nano ampere), when the scale change nanoscale

Measurement jump down and a sharp drop was seen in the Graf. 

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Different ranges use different setups to measure.  In the case of current, it would be a different sense resistor.  That could easily account for a rapid change in current.

In general, it is a good idea to just keep with a single range when doing sweeps like this.