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

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coldframe:

--- Quote from: Dr. Frank on February 18, 2014, 05:42:26 pm ---I asked you to make a test in 2W Ohm, shorting High and Low with a simple laboratory cable with good plugs.

What you are showing, looks not so good.

If you simply do the test, you can see, if the 2W mode is working correctly and if the zero is properly calobrated, after your repair.

Frank

--- End quote ---

I am sorry for the delay in my response.
Crash my Laptop, I have sent my Laptop be mended.

Would you Read The Personal Message?

Thanx

Dr. Frank:
Hello Coldframe,

sorry, it took me a while to shoot "speaking" photos (I hope so).

Just repeat your measurements, like I show you in the pictures.
Use 6 digit, slow mode.

Pic 1: in 2W mode, short input with a decent (good) cable. Check, if reading is a few milli - Ohm.

(See my 34401A, it still has 22mOhm, although it has been calibrated after the repair.
The switch is clean now, but worn-out. That still leads to changing readings, when using front/rear switch,  but now several mOhm only, and that does not disturb the readings)

Pic 2: Use Null function to remove the offset.

Pic 3: The 10 Ohm resistor is now measured correctly in 2W mode

Pic 4: 4W mode does not need Null math. The reading is even smaller compared to 2W Ohm mode with Null.

Pic 5: The resistor is soldered, that is better than clamping. Small resistor values always need 4 pole connection.

Please tell me, what you have measured.
Good luck.

Frank

coldframe:

--- Quote from: Dr. Frank on February 23, 2014, 06:47:44 pm ---Hello Coldframe,

Pic 1: in 2W mode, short input with a decent (good) cable. Check, if reading is a few milli - Ohm.

(See my 34401A, it still has 22mOhm, although it has been calibrated after the repair.
The switch is clean now, but worn-out. That still leads to changing readings, when using front/rear switch,  but now several mOhm only, and that does not disturb the readings)

Pic 2: Use Null function to remove the offset.

Pic 3: The 10 Ohm resistor is now measured correctly in 2W mode

Pic 4: 4W mode does not need Null math. The reading is even smaller compared to 2W Ohm mode with Null.

Pic 5: The resistor is soldered, that is better than clamping. Small resistor values always need 4 pole connection.

Please tell me, what you have measured.
Good luck.

Frank

--- End quote ---

Hi Dr Frank,

This is My Test Result, the Order are the same.

First of all,  press the button for the 2W Ohm and slow 6 Digit Mode Setting (A: MEAS MENU)

Pic 1: 0.09Ohm, Sometime 0.2Ohm... variable

Pic 6: When I Measure 2W Ohm Reading Value Increse  as time passes, This is My Problem
* This is Not Agilent, old HP :)
 
Thank you for your consideration.
Danke schön!

Dr. Frank:
Ok, then your instrument still has a BIG problem with the front/rear switch.

You can test that, if you short the input in 2W mode, and engage (press) the front / rear switch.
After returning to "front", the reading will increase strongly, perhaps several ohm already, I assume.

Then try pressing this button a little bit, not completely, you will see the zero-reading change a lot.

I have the same problem with my cleaned switch, but not so strong.

If nothing helps, order a spare switch from agilent.

PS: The "old" HP 34401A are still good, but switches are always a problem.

The HP3458A has a similar switch, same supplier, same construction, it's about 13 years old, and  it shows also increased and unstable resistance on the 2W Ohm mode, but not yet so strong, also.

Frank

coldframe:

--- Quote from: Dr. Frank on February 24, 2014, 08:08:47 am ---Ok, then your instrument still has a BIG problem with the front/rear switch.

You can test that, if you short the input in 2W mode, and engage (press) the front rear switch.
After returning to "front", the reading will increase strongly, perhaps several oohm already, I assume.

Then try pressing this button a little be, not completely, you will see the zero-reading change a lot.

I have the same problem with my cleaned switch, but not so strong.

If nothing helps, order a spare switch from agilent.

PS: The "old" HP 34401A are still good, but switches are always a problem.

The HP3458A has a similar switch, same supplier, same construction, it's about 13 years old, and  it shows also increased and unstable resistance on the 2W Ohm mode, but not yet so strong, also.

Frank

--- End quote ---

Yeah, I guess so.
After change a part, I'll let you know the result

Thank you Sir.

P.S
I have not one but seven 34401A
This is My Fisrt, Oldest, Favorite, Still Good Condition Except 2W Ohm :)

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