Understanding current measurement on an irregular waveform

[tempneff]

I hoped to use a Keithley 2400 source meter to generate a ~120Hz AC signal by outputting a 2-point sweep from 1A to -1A on an infinite trigger. The waveform image is attached below.

The end goal is a resistance measurement for bulk semiconductor materials, we prefer AC measurement to avoid thermoelectric drifts. To validate my input current I am measuring AC amperage through a verified 1.01 ohm resistor with a Keithley 2000-20 multimeter.

The meter measures .94A AC during the sweep. If I send 1A without sweeping and read DC current, it measures 1.01A; as expected.

I'd like to better understand the difference in magnitude. How is the measurement impacted by an "AC" current. Is there something problematic math-wise by not sending a sine wave.

 

[berkeman]

Why are there dwells at 0A when switching polarity? Is that maybe where the 7% error is coming from?

 

[tempneff]

Could be. I think it is inherent to the timing of the source meter. I have the delay set to zero, but we know that isn't possible.

 

[berkeman]

Is there a way to set the source to be 2App square wave with a -1A offset, instead of it being the two point sweep? I'm not familiar with that generator...