I'm wondering if this is my meter or there is a general ADC problem.

Here's what's happening:

If I measure the current through a 1k resistor from a .5V DC source I get ~.418 mA's on the 1mA scale. (Actually I've measured the resistance at 985.50 ohms and the DC source at .497V but this is close enough I think if anyone wishes to duplicate my error).

If I measure the current on the 10mA scale I get a correct reading of .504 amps.

So you would think there's a problem with my 1mA scale but if I measure low current on the scale, say a 10k resistor with a .5VDC source I get the correct reading on the 1mA scale. As I move up the scale the error increases.

Thanks for your time and help,

Robert

Here's what's happening:

If I measure the current through a 1k resistor from a .5V DC source I get ~.418 mA's on the 1mA scale. (Actually I've measured the resistance at 985.50 ohms and the DC source at .497V but this is close enough I think if anyone wishes to duplicate my error).

If I measure the current on the 10mA scale I get a correct reading of .504 amps.

So you would think there's a problem with my 1mA scale but if I measure low current on the scale, say a 10k resistor with a .5VDC source I get the correct reading on the 1mA scale. As I move up the scale the error increases.

Thanks for your time and help,

Robert

this is no anomaly, but simply caused by the burden voltage over the internal shunt resistor of the 34410A, which has to be taken into account, like on any other DMM also.

See specification, page 131 of the 'User's Guide':

DC Current, Shunt Resistor:

0.1 Ohm for 1A,3A

2 Ohm for 10mA, 100mA

200 Ohm for 100uA, 1mA

In your circuitry, the total resistance on the 1mA range is 985 + 200 Ohm = 1185 Ohm.

That calculates the current to: I = 0.497V / 1185 Ohm = 0.419mA

On the 10mA range, the total resistance is 987 Ohm, so the current is calculated to 0.497 V / 987 Ohm = 0.504 mA.

Therefore, everything is fine with your instrument.

Frank