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Agilent U1733C 100kHz mode: unstable high readings normal?
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Per Hansson:
Got this Agilent U1733C on eBay around 3 years ago, I have not used it extensively but for my simple needs it has been fine.
But yesterday I was testing some ultra low ESR capacitors and everything looked fine first but then I realized all readings at 100kHz where an order of magnitude too low.
That is to say the datasheet says 8mΩ but the meter read 0.0008Ω, not 0.0080Ω as it should be, it might always have been like this.

So I used a Pomona MDP-S-2 shorting bar to take the below readings.
Note how in 100kHz mode it is arbitrarily high.
Doing a user calibration with the shorting bar I get better readings.
But they are still unstable at 100kHz.

I opened the unit up and it is evident someone had a go at it:
One of the plastic PCB supports was broken off.
And the PCB had soldering paste, dirt and solderballs around U18 & U6 (NXP 74HC4053D).
I cleaned it off with IPA but that did not affect the readings at all.
The SMD electrolytic caps C19 and C83 do infact look like they are bulging.
And C44 near the above mentioned area looks like it went through a war, they all read ok-ish in circuit ESR except maybe C4 that was twice of the others.

The unit has firmware version: Pro 00.25
Maybe someone else has a similar meter and could remake the tests to give me an idea what is normal?
Also maybe someone can explain how to switch from OS-Factory to OS-User without changing the startup default setup value to either one?


--- Code: ---OS-Factory.
Pomona MDP-S-2 shorting bar:
DCR: 0.0012 Ω

R 100Hz: 0.0086 Ω
R 120Hz: 0.0086 Ω
R 1kHz:  0.0086 Ω
R 10kHz: 0.0078 Ω
R 100kHz:0.0365 Ω


Z 100Hz: 0.0086 Ω
Z 120Hz: 0.0086 Ω
Z 1kHz:  0.0086 Ω
Z 10kHz: 0.0085 Ω
Z 100kHz:0.0425 Ω

L 100Hz: 000.1 µH
L 120Hz: 000.1 µH
L 1kHz:  00.00 µH
L 10kHz: 0.055 µH
L 100kHz:0.035 µH

--- End code ---

--- Code: ---OS-User.
Pomona MDP-S-2 shorting bar:
DCR: 0.0002 Ω

R 100Hz: 0.0000 Ω
R 120Hz: 0.0000 Ω
R 1kHz:  0.0000 Ω
R 10kHz: 0.0001 Ω
R 100kHz:0.0012 Ω


Z 100Hz: 0.0002 Ω
Z 120Hz: 0.0000 Ω
Z 1kHz:  0.0000 Ω
Z 10kHz: 0.0002 Ω
Z 100kHz:0.0016 Ω

L 100Hz: 000.0 µH
L 120Hz: 000.0 µH
L 1kHz:  00.00 µH
L 10kHz: 0.000 µH
L 100kHz:0.000 µH

--- End code ---
Per Hansson:
Rewatching Daves teardown video #234 of the U1733C I noticed the same area has flux residue on his board too.
Maybe it is from hand soldering the through hole power connector in that area? If so it's a bit how'ya doing to not clean the flux residues!  :wtf:
Yesterdays numbers where with an ambient temperature of around 30°C I redid them this morning at around 20°C
The numbers are then around 15% lower, except for the 100kHz ones that are ca 50% lower and DCR that goes in the opposite direction.
Reducing the temp to ca 10°C by putting the meter in the fridge for a couple hours brought another 15%.
And now that the temp is up to 30°C again the same numbers are back, so is this normal behavior? was the meter calibrated in a fridge at Agilent?  :-/O
Also can someone ID the brand and model of those SMD electrolytic caps?


--- Code: ---OS-Factory.
Pomona MDP-S-2 shorting bar:
30°C:   20°C:    10°C:
DCR: 0.0012 Ω 0,0037 Ω 0,0098 Ω
R 100Hz: 0.0086 Ω 0,0071 Ω 0,0062 Ω
R 120Hz: 0.0086 Ω 0,0071 Ω 0,0062 Ω
R 1kHz:  0.0086 Ω 0,0071 Ω 0,0062 Ω
R 10kHz: 0.0078 Ω 0,0066 Ω 0,0058 Ω
R 100kHz:0.0365 Ω 0,0180 Ω 0,0060 Ω

--- End code ---
TheSteve:
Specified performance is at 23 degree +- 5 degrees.
RoV:
I think the ESR accuracy of the U1733C @100 kHz, even in the lowest full-scale range, is much worse than 0.8 mohm.
Check annexed page of the User's Guide: if I am reading correctly, in the 2 ohm range, even ignoring Q (note 4), we get 1% of 2 ohm + 50 digits, or 0.02 ohm + 50 digits.
Per Hansson:
Thanks for pointing that out TheSteve and RoV!
I still would really appreciate it if someone with a U1733C could reproduce my tests with a shorting bar: it would easy my mind :)
Just to give an example if I measure the actual ESR of a low ESR Chemi-Con PSG polymer capacitor in the OS-factory mode with no test leads it is all over the place:


--- Code: ---OS-Factory.
Chemi-Con PSG 1000µF solid polymer capacitor rated 8mΩ (0.0080Ω) at 100kHz:
ESR 100Hz:  0.0207 Ω
ESR 120Hz:  0.0203 Ω
ESR 1kHz:   0.0064 Ω
ESR 10kHz:  0.0044 Ω
ESR 100kHz: 0.0244 Ω

--- End code ---

Of course with a tolerance of 1% + 50 counts at 100kHz a reading of 0.0250Ω + the expected ESR of the capacitor is within tolerance.
But then with specifications like that I don't know that this meter is any better than the venerable $20 component tester! :D
But just to be clear it is that the values form a "bathtub curve" by significantly going up at 100kHz that concern me...
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