keithley 2000 (2015) ac current problem

[linux-works]

I bought a 2015 locally and am testing it out now.

all the ranges seem ok except I have a question about ac current.  I bought the DMMcheck device (voltagestandard.com) and I'm using the ac current (1ma) test on the keithley but I'm not seeing a reliable 1ma.  sometimes I see nothing (same as leads left unconnected) and only when I cycle thru the range (to 1A range) do I see something that looks close to 1ma.

on the dc-i range, things are fine; I see 1.000something mA on dc-i.  but on ac-i, it looks like there is only the 1A and 3A ranges and so I won't see a 1.something reading, but a 0.001something reading.  is that correct?

the fuse on the amp terminal is fine (esp since dc-i works just great).

I have some time to eval this meter before returning it or keeping it.  overall, it seems nice but I'm concerned that ac-i is not right.

fwiw, when I check the ac-i on my fluke 45, it checks out very very close to 1mA so I'm pretty sure my brand new dmmcheck device is working ok.

[linux-works]

btw, here's a photo of the dmm check device on the keithley, showing pretty close to 5v

[iloveelectronics]

I have the exact same question with a used 2000 I have! Everything seems fine except ACI. I am having a hard time finding a calibration lab locally that could calibrate this thing...

[ckm]

I have a 2015 and a DMMcheck as well.  Everything is within 0.02% other than AC current, which is 10% out. 

This would seem to be out of spec:

Code: [Select]

ACCURACY1: ±(% of reading + % of range), 23°C ±5 °C
CURRENT CALIBRATION
                  3 Hz-10 Hz   |  10 Hz–3 kHz  |  3 kHz-5 kHz
-------------------------------+---------------+----------------
1.000000 A-1 ?A    0.30 + 0.04 |  0.10 + 0.04  |  0.14 + 0.04
3.00000 A-10 ?A    0.35 + 0.06 |  0.15 + 0.06  |  0.18 + 0.06

That said, it may be something to do with DMMcheck or it could also be a function of the probes/leads.   I've had issues with AC current & DMMcheck with other meters.

Although it's unrelated and not in the same class,  I noticed on my Uni-T U71D that in the specs, the mA range only goes to 400mA, then the 1A range takes over.  Which means there is a hole between 400mA and 1A where nothing is measured.  Perhaps the same thing is true with Keithley or there is a lack of accuracy in that range (e.g. it can't do sub .5A accurately), I haven't looked at the manual closely enough.   What's clear is that if you want to measure things in the mA AC range, a 2015 is not the meter to get....

I'm not personally inclined to test any further since I have a Fluke 189 which is within 0.5% on AC current, but it is interesting that 3 different meters have the same issue.  Amazingly, the Fluke is with 0.09% overall, which is really very, very good for a 10+ year old handheld....   No wonder they retain their value.

P.S. Attached is my test report.  I do this for all my gear so I know what is most accurate....

[quarks]

The 2015 does not offer low ACI ranges, therefore 1mA in the 1A range is only 0.1% of the range and that is just to low to measure accuratly. 

[KJDS]

Here's a video showing the effect.