Electronics > Repair
Agilent 34401A Bubble on PCB ... can it be saved ? (SOLVED)
<< < (24/24)
coromonadalix:
it is normal or not  upon  what use you intend to do with it

precision means calibration / certifications at 1 or 2 years intervals

basic use means, you do basic or non precise checks   but not undergo the cals certs

but at some point  you will need to be sure of this meter and it's capacities, at 6.5 digit,  it is not a toy ... do you accept to use it  not calibrated an live with uncertainties ....

i personally would not,  it is a 0.035% precision meter if i recall ...  or more in the 0,01% in resistances  ....
The_Spectrum.A_idiot:

--- Quote from: coromonadalix on September 25, 2024, 04:23:29 pm ---it is normal or not  upon  what use you intend to do with it

precision means calibration / certifications at 1 or 2 years intervals

basic use means, you do precise checks   but not undergo the cals certs

but at some point  you will need to be sure of this meter and it's capacities, at 6.5 digit,  it is not a toy ... do you accept to use it  not calibrated an live with uncertainties ....

i personally would not

--- End quote ---

As soon as I do it once and I know that is ok, then I can start to trust it.

I can repeat the cal every 5 years or so just for my sake , I am not a professional but I want to have confidence in my readings.

Thanks we have a similar mind set :D

Thank you in advance

The Spectrum
Kleinstein:
If not needed for some professional use the question is if one really needs a formal calibration. Form most hobby use one may not really care that much, though a good test to get confidence is still wellcome.
The usualy calibration is just the testing - often without giving the actual readings, but just a pass / fail. The change of the cal constants in the meter is called adjustment and this may cost extra and is rarely done, as long as the meter is still in specs. In my oppinion one should consider readjustment, or a marking on the meter if it comes close (e.g. 75%)  to the accuracy limits, as there is also a drift component and the calibration should give confidence that the meter will meet the specs for the next 1 or 2 years.
The 34401 are usually quite stable and an re-adjustment is rarely needed.

The repair in the ohms section should not have effected the amps and voltage part. The resistor part can be effected a little, from the offset of the OP-amp that was changed. Up to 100 µV offset relative to 5 V would be 20 ppm contribution from the offset and 2 OP-amps in the circuit. For the 10 M range this would be 10 x higher with only 0.5 V ref. voltage for the 2nd OP-amp. In addition the bias / leakage current could be relevant there too. So there is a chance that the 10 M range can be out of spec.

The self test is not very strict and does not cover all aspects. From the service manual the last 2 tests that caused an error have a test limit of +-20% for the current - so not at all strict. So it may not trigger on a lesser problem that can still make the meter to fail. Testing to better than 10% is not that hard.

One may not need super accurate parts to do some testing considerably stricter than the self tests. Some of the tests also cover things not covered by the self tests and often not checked during calibration. A few tests that can be done relatively easy are:
1) input bias with a low loss, low leakage capacitor (e.g. 1-10 nF PP or PS type)
2) sum of 2 resistors to check the linearity in the resistance mode  (can be effected by leakage).  With some care in the environment, relatively common 100 ppm/K parts can be sufficient. For 4.7 M+4.7 M even lower grades can be OK.
3) drift during the warm up, especially for zero voltage and resistors
4) a turn over test with a 9 V battery or similar. This may need some care to keep the battery undisturbed and repeats to check.
5) A check of the noise with a short.
6) Check some resistors (e.g. 10K, 100K, 1 M) in 2 ranges each.
7) zero resistor reading
8) AC reading in a square wave with accurate amplitude (e.g. CMOS gate with 50/50 ratio)
Doing the tests is a way to get familiar with the meter too.
The_Spectrum.A_idiot:

--- Quote from: Kleinstein on September 25, 2024, 06:23:16 pm ---If not needed for some professional use the question is if one really needs a formal calibration. Form most hobby use one may not really care that much, though a good test to get confidence is still wellcome.
The usualy calibration is just the testing - often without giving the actual readings, but just a pass / fail. The change of the cal constants in the meter is called adjustment and this may cost extra and is rarely done, as long as the meter is still in specs. In my oppinion one should consider readjustment, or a marking on the meter if it comes close (e.g. 75%)  to the accuracy limits, as there is also a drift component and the calibration should give confidence that the meter will meet the specs for the next 1 or 2 years.
The 34401 are usually quite stable and an re-adjustment is rarely needed.

The repair in the ohms section should not have effected the amps and voltage part. The resistor part can be effected a little, from the offset of the OP-amp that was changed. Up to 100 µV offset relative to 5 V would be 20 ppm contribution from the offset and 2 OP-amps in the circuit. For the 10 M range this would be 10 x higher with only 0.5 V ref. voltage for the 2nd OP-amp. In addition the bias / leakage current could be relevant there too. So there is a chance that the 10 M range can be out of spec.

The self test is not very strict and does not cover all aspects. From the service manual the last 2 tests that caused an error have a test limit of +-20% for the current - so not at all strict. So it may not trigger on a lesser problem that can still make the meter to fail. Testing to better than 10% is not that hard.

One may not need super accurate parts to do some testing considerably stricter than the self tests. Some of the tests also cover things not covered by the self tests and often not checked during calibration. A few tests that can be done relatively easy are:
1) input bias with a low loss, low leakage capacitor (e.g. 1-10 nF PP or PS type)
2) sum of 2 resistors to check the linearity in the resistance mode  (can be effected by leakage).  With some care in the environment, relatively common 100 ppm/K parts can be sufficient. For 4.7 M+4.7 M even lower grades can be OK.
3) drift during the warm up, especially for zero voltage and resistors
4) a turn over test with a 9 V battery or similar. This may need some care to keep the battery undisturbed and repeats to check.
5) A check of the noise with a short.
6) Check some resistors (e.g. 10K, 100K, 1 M) in 2 ranges each.
7) zero resistor reading
8) AC reading in a square wave with accurate amplitude (e.g. CMOS gate with 50/50 ratio)
Doing the tests is a way to get familiar with the meter too.

--- End quote ---

Thank you very much for the pointers.

The reason I am leaning heavily towards calibration and adjustment is the sole reason that the instrument comes from an UNKNOWN environment with unknown calibration verification. No cert has accompanied the meter.

So this lack of traceability is the issue.

Plus as I said its all about trust.

Thank you in advance
Navigation
Message Index
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod