Keithley 2010 AC Accuracy and Calibration Question

[J-R]

Was a bit surprised at the perhaps low AC performance.  It's only 6.5 digits in AC modes, there is no mA AC range and the accuracy isn't that great IMHO, although it meets the 90 day spec.  My HP34401A and Keithley 197A seem to be better choices for this task.

Since there can be a large difference between spec and real-world, what have other 2010 owners seen from it with regard to AC accuracy?  Is it worth trying to get it tightened up a bit?  Calibration/adjustment+data will cost as much as I paid for the unit so I'm on the fence.

[Kleinstein]

The 2010 is a nice meter for DC, but not that great for AC. The accuracy with the analog RMS chips is just limited.  So I am afraid that even with extra test the accuracy would not be great. So I don't think it would be worth spending much in a more detailed AC calibration.  If really better AC performce is needed I would consider a separate meter like the KS34461.

Not having mA AC ranges is a little odd. 10 mA are not yet the low and schould be possible from the HW side. 

[J-R]

Some quick, 1 year accuracy calculations, 5VAC 60Hz:
34401A: +/- 0.006V
197A: +/- 0.0275V
2010: +/- 0.006V

The 34401A and 2010 are actually very close on paper, but in my case the 34401A has had the fortune of a recent calibration.
According to the calibration data, my 34401A exceeds ACV specs by about a factor of 10, and in some case 100+.
So the 2010, even calibrated, is unlikely to outclass the 34401A, so not worth the cost.
Going in to this, I was just expecting the 2010 to be x-amount better.  Honestly, I didn't even notice until running these tests that AC was only 6.5 digits, the sneaky bastards!

The 5.5 digit 197A definitely bests the pitiful published specs.

The 10mA current range is technically a hidden feature on the 34401A, which I unlocked as soon as I got it.  No specs are listed, but it's very good, 3-4 digits, no problem.

I'm sure the varying frequency response is also coming in to play here, as mentioned by HKJ: https://lygte-info.dk/info/DMMFrequencyResponse%20UK.html

[Kleinstein]

The 34401, Keithley 197 and likely also the 2010 use the AD637 true RMS chip and are this limited by it's performance. There can be only additional limitations from the input stage to get more frequency dependence, that can effect the K197. There is just a limit to how good the analog RMS chips are. So even the 8 drigt Keithley2000 is not that much better with AC. 

Not having a mA AC range with the 2010 is a little odd, though the same limitation with the 34401. A point could be the extra effort for the calibration - still a bit strange to skip on this in this price range. I don't see a technical reason to skip mA AC. Getting to the low  µA AC range can be tricky or at least limited BW.

[J-R]

Since my 34401A calibration data doesn't include the "secret" AC 10 mA range, the only standard I can reference is 1mA from the DMMCheckPlus, which is +/- 0.002mA.  In that case the 34401A and 197A were both good for 1.00mA at least.  The 2010 of course had a rough time via the 1A range, at approximately 1.5mA.

The lack of mA and even uA was probably a specific choice as even the cheapest handhelds can do this.