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[SOLVED]HP/AGILENT/KEYSIGHT 34401A 2W Ohm Problem

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coldframe:
When I measure 2-wire ohms I get an offset in the reading.
 
For example.
I will get readings from 31 Ohms in 2-wire mode when measuring a 10 ohm resistor.
* In 4-wire ohms mode,  an accurate stable reading of 10.0 ohms.
* This is my 10 Ohm resistor Information  http://www.te.com/catalog/pn/en/1624323-4

This resistor measures a stable 10.0 ohms on a known good meter.
Any Idea?

Best regards.

free_electron:
most likely the output protection cascade for the meter has taken a hit from overvoltage.

in 4 wire mode this cascade is bypassed and the current sources feed the 4terminal output directly.
the cascade is a chain of 6 or 7 transistors. most likely one of em is fried.

look in the schematic it is very easy to find the cascade

coldframe:

--- Quote from: free_electron on January 24, 2014, 01:48:43 am ---most likely the output protection cascade for the meter has taken a hit from overvoltage.

in 4 wire mode this cascade is bypassed and the current sources feed the 4terminal output directly.
the cascade is a chain of 6 or 7 transistors. most likely one of em is fried.

look in the schematic it is very easy to find the cascade

--- End quote ---

free_electron..

I have often heard your name., I'm honored to meet you.

I'll get it checked soon.
Thank you for the tip.

*  most likely one of em is fried. , What does the "em" stand for?

Fluxed Matter:
That's slang in the US for them.

SeanB:
"em" means them. Replace all the transistors with new from the same batch and you will only have to test them to see which was faulty. They are cheap.

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