Keithley 2400 driver: source and sense range mixing

[panasee]

Hello, I found a confusing range setting in Keithley 2400 driver:

        self.add_parameter(
            "rangev",
            get_cmd="SENS:VOLT:RANG?",
            get_parser=float,
            set_cmd="SOUR:VOLT:RANG {:f}",
            label="Voltage range",
        )

Above is the range parameter for Keithley 2400. Here the get_cmd retrieves the sense range while the set_cmd tries to set the source range. From the manual of Keithley 2400, there can be two different ranges for sense and source. Are there special considerations for that?

[jenshnielsen]

I don't have much context for this but the same is done for the current limit so I would guess it's probably intentional and an attempt to enable it to be used in both modes. That being said I don't think this is correct and I suggest that we add a parameter for both the sense and the set limit independently. @panasee would you be willing to open a pr to do that?

[panasee]

I've further tested this with a 2401 meter. It seems the sense range is bound to the source range for the sourcing property. When I tried to set the sense range for the sourcing property, an error appeared at the meter's front panel (no error message from communication): "Invalid with source read-back on" (+823 error in the manual). This may be the reason for the original code writing.

I didn't find more details about the "source read-back" in the manual so I can't guarantee that it's a common feature for all 2400-series meters.

I think the range parameters can be left as is for now although it can be confusing.

The code I used is attached here:

meter.mode("CURR")
meter.curr(1E-6)
meter.output(True)
meter.write("SENS:CURR:RANG 0.01")
meter.write("SOUR:CURR:RANG 0.001")
print(f"final source curr range: {meter.ask("SENS:CURR:RANG?")}")
print(f"final sense curr range: {meter.ask("SOUR:CURR:RANG?")}")
meter.output(False)

print("="*20)

meter.mode("VOLT")
meter.volt(1.5)
meter.output(True)
meter.write("SOUR:VOLT:RANG 10")
meter.write("SENS:VOLT:RANG 1")
print(f"final source volt range: {meter.ask("SENS:VOLT:RANG?")}")
print(f"final sense volt range: {meter.ask("SOUR:VOLT:RANG?")}")
meter.output(False)

The output is:

final source curr range: 1.050000E-03
final sense curr range: 1.050000E-03
====================
final source volt range: 21.00
final sense volt range: 21.00

Apparently, the "SENS:CURR(VOLT):RANG" caused no effect here.

[panasee]

Sometimes, the meter will give some error messages that only show up on its front panel. Is there a way to capture them in python? This could be very useful for debugging.