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Agilent 34401a multimeter limited to 0.4a?

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JDubU:
Set the 34401A to "DC I" and measure the resistance between the "3A" and "Lo" inputs using your Fluke DMM.

HighVoltage:
Hook back up your 34401A to measure the DC current.

1. Measure the voltage drop (V DC) across the input to the 34401A with the Fluke 115
How much do you read?

2. Install a shortage wire across the input to the 34401A.
Now the 34401A should read almost 0 A in current.
Does the power supply now increases to almost 1A again?

salvagedcircuitry:
@JDubU resistance between the "3A" and "Lo" inputs is 5.6ohms


--- Quote from: HighVoltage on February 22, 2019, 05:23:23 pm ---Hook back up your 34401A to measure the DC current.

1. Measure the voltage drop (V DC) across the input to the 34401A with the Fluke 115
How much do you read?

2. Install a shortage wire across the input to the 34401A.
Now the 34401A should read almost 0 A in current.
Does the power supply now increases to almost 1A again?

--- End quote ---

1) The voltage drop is about 0.2v DC
2) Yes, that is correct.

So the end result is that burden voltage has a lot more impact on current measurements on my 34401a than my fluke 115. Ok that makes sense now. Thanks guys  :-+

JDubU:
FYI:

Here is an excerpt from the 34401A service manual showing shunt resistor values for each current range setting.
 

HighVoltage:

--- Quote from: salvagedcircuitry on February 22, 2019, 05:48:57 pm ---So the end result is that burden voltage has a lot more impact on current measurements on my 34401a than my fluke 115. Ok that makes sense now. Thanks guys  :-+

--- End quote ---
Yes, this is a easy trap to fall in to and a good lesson to learn about the 34401A current measurements.

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