34901A logger card current measurement burden resistor change during logging

[KlausKragelund]

Hi

I am using a 34901A logger card for current measurement (channel 21)

Page 21 of this link:

https://www.avionteq.com/Document/34901A-specification-sheet.pdf

I have the unit logging voltages also, and have set CH21 to manual range 1A

But when the logger scans the channel, the burden resistors is not fixed on CH21. Seems like it normally shorts out the burden resistor when other channels are captured and opens when it scans the current

That means the burden resistor changes in the measurement, and affects other measurements.

Is it possible to have the burden resistor present always, so the resistance does not change?

Thanks

Klaus

[TizianoHV]

I had your same problem with my 34901A. I almost never use the current channels. I use one of the voltage channels with an external shunt and the math function to display the value scaled in amps.

The 34970A uses a 0.1Ohm resistor for the 1A range, and 10Ohm for the 10-100mA ranges. The 0.1Ohm resistor is nothing special.


What level of accuracy do you need? I use a 0.2Ohm 5W 20ppm/°C up to 4A or a 1Ohm film resistor for lower currents (consisting of multiple resistors in parallel).