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Keysight DMM - Yay or nay?

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Kleinstein:
Analog true RMS is naturally slow. To get good accuracy at 20 Hz it needs a rather slow settling filter and this gives a naturally somewhat sluggish reaction. Some chips are worse than others in this respect (worst case things get even slower at low votlage), but even the good ones are slow. One should still see a first reaction reasonably fast, but the final accuracy may well need 5 seconds of waiting.
If implemented poorly AC autoranging could suffer quite a bit, though there are ways around this.

The DMM6500 and KS346x meters use digital RMS and can react quite fast in AC mode (stable final reading after some 200 ms - don't know the details on these meters). One can already see the difference with handheld meters - some of the newer, more low cost true RMS meters use digital RMS and offer surprisingly fast AC settling.
The SDM3065 uses a classical analog RMS chip.

At a  slightly higher price point there is also the Fluke 8845 DMM as a possible candidate - not my favorite, but just to add to the list.

Occasional failing AC is a potential risk. It could be from a relay problem - this is indeed bad and a good reason not to trust any such meter to check if there is no mains. At least German regulations wants you to use a dedicated tool for this and not a normal DMM, let alone a bench DMM.

ch_scr:
My father has the HMC8012 as his bench DMM basically since it came out. It is not a bad little unit, but it came out around the time of the Hameg merger and it feels like they forgot to continue FW development. The last firmware is from 2017. And not because the FW on the unit is perfect, it's not Rigol-level-buggy, don't get me wrong, but the control concept feels off and is not totally consistent, some buttons seem almost unused on the UI. And a modern DMM with color LCD but without plotting? Seriously? There are basic statistics but no histogram or tracking view - soo much lost potential there alone! The interleaved voltage / current measurement without relay switching is a very nice feature for a general bench DMM, much appreciated, as is the fast boot time. It is not a bad instrument, works well in general, but it is really let down by what feels like abandoned development.

Traceless:

--- Quote from: Kleinstein on March 02, 2022, 09:41:47 am ---But the final accuracy may well need 5 seconds of waiting.
...
Occasional failing AC is a potential risk. It could be from a relay problem - this is indeed bad and a good reason not to trust any such meter to check if there is no mains.

--- End quote ---

I don't think there is a defect with my DMM. I think what is going on is this:

When I take an AC measurement the DMM takes time - 5s sounds about right. The catch is: My DMM seems to display nothing until it has a stable reading (-> 5s delay plus the autoranging delay that varies depending on how many ranges it has to cycle through). Now when there is bad contact, due to oxidized or dirty joints or just because the probes are sliding a bit when applying pressure and contact is lost for a fraction of a second the measurement resets and the DMM starts over trying to get a stable value. So basically AC measurements are not constant time but vary depending on the current circumstance. So you can never be sure if you waited long enough. I ordered some new super sharp probes to see if that helps with the issue.


--- Quote from: Kleinstein on March 02, 2022, 09:41:47 am ---At least German regulations wants you to use a dedicated tool for this and not a normal DMM, let alone a bench DMM.

--- End quote ---

I had replaced the fuse in a 24V SMPs adapter and just wanted to check if I had mains at the input filter after replacing the fuse. I didn't get a reading in time on my bench DMM. All plugs were connected and my isolation variac was turned on, also I checked the fuse. Knowing about the delays I got suspicious grabed my Aneng 8009 and voila mains present. The Aneng is just a lot faster than the bench DMM. Workarounds are the following:

- Patience (and probably better probes)
- Select range manually
- Increase the trigger speed

The problem here is that the meter does not save the trigger setting when turned off, also the least significant digits become very jittery when increasing the trigger speed. Ultimately that means that I need to keep manually switching between low and high trigger speed, depending on if I want to measure presence of mains or do high precision measurements on the secondary side. All of this is doable and otherwise the meter is really good but those constant user interactions, switching between low and fast trigger and manually changing the range get really annoying. Luckily that only is an issue when I work on PSUs in other cases the meter does a very good job.


--- Quote from: Kleinstein on March 02, 2022, 09:41:47 am ---At a  slightly higher price point there is also the Fluke 8845 DMM as a possible candidate - not my favorite, but just to add to the list.

--- End quote ---

Good tip I added the Fluke to the list, though feature-wise the even more expensive 8846A is probably closer to the 34465A.

@ch_scr: Thanks for reporting these experiences. That confirms my suspicion that the HMC8012 does not offer a good value (any more) for its price.

Markus2801A:
Hello

I just want to bring in the GW-Instek GDM-906x Series with two types namely GDM- GDM-9060 and the  GDM-9061

https://www.gwinstek.com/en-global/products/detail/GDM-906x

What do you guys think of them?

Kind regards!
Markus from Austria

mawyatt:
We also discovered some charge injection on the DMM inputs, and the DMM6500 seemed to have slightly more.


https://www.eevblog.com/forum/testgear/dmm6500-glitch-on-dcv/msg3753929/#msg3753929

Best,

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