Anyone who has ever done thermal testing knows it can take a fair amount of time (weeks, months). With the handhelds, even if I wanted to run a complex test, the data would have to be collected manually or possibly using multiple cameras inside the chamber. A lot to invest for some cheap meters. I'll leave that to the next person.
So we are back to what test could be ran in the shortest time that yields the most useful information. Again, I am open to suggestions and have posted a proposal that Alm has weighed in on. Feel free to do the same.
Sorry you feel that way Dave. I would say if anyone was the fool, it was me. There is little I can do at this point beyond not mentioning the meter and pulling down the videos. If you like I can remove the last one as well. Your call.
So we are back to what test could be ran in the shortest time that yields the most useful information. Again, I am open to suggestions and have posted a proposal that Alm has weighed in on. Feel free to do the same.
Fair enough, so to be constructive, I agree with alm and as I stated before him, I think it should be done at volts range.. Even 1-2V is much better than millivolts (some would even say thousands times better ). Complication is with the fact that meters can have 1,2,3,4,5,6V ranges. So full scale will be different for each one.
That can be mitigated by testing at each full range (or close to full range) and calculating and specifying tempco with percentage instead of absolute values..
So you have meters with 4, 5 and 6V range, connect them to 4V and fire away.. Or you can test meters with same ranges together....
But simply testing at 1-2V would be enough to make it much better than testing at millivolts range..
If you are comparing meter tempcos then just a simple delta at two temps (plus room temp) on a fixed DCV range at close to full scale.
Meter data sheet specs are typically given for room temp (23degC) +/- 5 degC. So I'd pick 10degC and 40degC as the other temps.
Room temp doesn't really take any extra time as you do it at the start of the thermal test (unless you don't work in a fairly controlled temp office environment like I do).
If you want to save extra time then just chose a temp in one direction from room temp. I'd suggest at least 20degC delta in any case. Positive or negative direction is a coin toss, doesn't really matter.
Saying 60C is not a real world thing is not true, many lift motor rooms here will regularly reach that and higher in summer, as they typically are brick and concrete slab buildings on top with a lovely reflective silver concentrator of the rest of the building cooking the walls all day. Sitting with almost zero cooling aside from air vents typically closed with rodent proofing and roach proofing mesh, and with 10kW of motor heat being dissipated in the room with it as well, and all the brake, controller and shaft heat rising up into there as well. If you are unlucky you get the older ones that are basically a tin shack, walls, roof and with a tin sheet door, basically a solar oven. You go in there and it might be 60C easily, and you work fast and take regular breaks out in the up to 40C cool outside. Your meter should work there though, you will be leaving it there while you go out for the break and the look for some water to drink.
You tend to get the hotter non room temp conditions a lot more than the cold ones, though you can also be working in a cold store with it sitting at -30C as well, though you probably are really only going to be concerned with rough resistance and continuity, and if voltage is present in about the right range in these conditions.
Sorry you feel that way Dave. I would say if anyone was the fool, it was me. There is little I can do at this point beyond not mentioning the meter and pulling down the videos. If you like I can remove the last one as well. Your call.
I never asked you to nor will I ask you to remove any videos. Entirely your call. I sent you an unreleased and unfinished meter and I can't and and don't want to stop you from doing what you want to do with it.
As an aside, I was surprised to see you doing more with it than I thought you wanted it for (i.e. some fun potentially blowing it up). I'm not really a follower of your videos or this thread so had no real idea about the seriousness you take all this stuff.
Sorry if you thought I was sending you a review unit, that wasn't my intention.
Just today some parts have changed again that affect the tempco and stability of the unit.
I should have ran my test at 10V and then looked at the mV as a percent change and really make those numbers look good. But instead, I ran the same test as before. 1mV, highest sensitivity range, -20 to 60C then calculate a TC from that by looking at the change in voltage / change in temp.
Want to know how the pre-production 121GW and Gossen M248B compare against my most stable meter, watch and find out.
Joe, this test is completely invalid. The meter you have is not the current pre-production unit, it's a prototype that does not have the current voltage reference or divider resistors. I mentioned this in the emails to you when I sent it, so I'm not sure why you tested this.
It is most definitely not representative of the final unit.
I'd appreciate if you don't do any more further testing on this unit as it will only confuse people.
Thanks.
The question, however, is will there be anything to measure? Even for -10°C to 40°C, the deviation for several meters was down to 1 LSD (i.e. down in quantization noise), see attached frame from Joe's video that I linked to in my previous post. If you limit the temperature range even more, pretty much all meters might score < 1 LSD, which makes the test not very sensitive (mediocre meter in this regard performs the same as an excellent meter).
is it really that interesting to focus on this detail?
Maybe the conclusion would just be that the temperature coefficient is negligible for many 3.5 digit meters, at least as far as gain error is concerned?
is it really that interesting to focus on this detail?For the normal person, I would hope not. But we could say the same thing about the transient testing. Is that interesting to the normal person? I would again say no but it does seem there is a small group of us who are interested in the subject. Maybe myself along with the other subscribers should seek help on a professional level.
If only there was something interesting to look at with a volt signal. Seeing a few counts of change is not much fun. Your idea about testing them with condensation is sounding better and better...
Maybe the two members who asked to see the 8002/8 tested over temp have an opinion on what they would like to see. Feel free to add to the mix.
Am I the only one confused about why a meter that is checked against two higher cost units and deemed to be pretty good, would go through yet another round of mods that effect the temperature performance? My guess is it must have been a side effect from another change and not that they are directly changing the reference circuit or attenuator network for lower drift. It would not make sense.
If only there was something interesting to look at with a volt signal. Seeing a few counts of change is not much fun. Your idea about testing them with condensation is sounding better and better...
It is a test, it can not be invalid (unless you compare it with manufacturer data - which you are not going to do)
And now we get to the root of the problem and why I changed the test method. I can go back to looking at 1V and run at an even less temperature swing but from the little bit I looked at it, I don't think you will learn much from it.
Am I the only one confused about why a meter that is checked against two higher cost units and deemed to be pretty good, would go through yet another round of mods that effect the temperature performance?
Am I the only one confused about why a meter that is checked against two higher cost units and deemed to be pretty good, would go through yet another round of mods that effect the temperature performance?
We missed something on the 50mV range.
Joe, do you have any idea how reproducible the 1 mV tests were? I.e. if you go back the next day and reconnect a meter, will it show the same results? If thermoelectrics indeed play a role, than I would expect a fair variation between runs due to how the cables are run and how temperature gradients across the cables are.
If only there was something interesting to look at with a volt signal. Seeing a few counts of change is not much fun. Your idea about testing them with condensation is sounding better and better...
Maybe the two members who asked to see the 8002/8 tested over temp have an opinion on what they would like to see. Feel free to add to the mix.
I think I was one of the two, I asked and still I ask you to test AN8008 - but in the original rig!
I'm not convinced that original test is completely invalid - on the contrary!
Even from previous posts is evident, and I agree with that, that test with narrower range of temperatures ( and 1V level) would probably mean "nothing to write home about".
If I were you, I would continue in that original test (-20 Deg C to +60 Deg C and 1mV), and when new 121GW is available to public, then test it too, please.
When UT181a is stable enough, let others be stable too.
It is a test, it can not be invalid (unless you compare it with manufacturer data - which you are not going to do)
Thank you in advance!
I was probably the other (unless there was someone else too). Personally I only cared about how they compare with each other (the meters). It didn't necessarily need to be real world usage. So I'd be fine with any test that can compare meters (i.e. multiple meters being tested under the same conditions), but being a beginner to electronics, I don't have a deep enough understanding to suggest some high quality methodology. I understand that the more points measured, the more valuable the data, but it would be fun to watch either way. It's not data to draw conclusions from (e.g. how much the drift would be at specific setting at specific temperature range), but it still gives an idea on what different meters display under the same or at least very similar working conditions.
But, if most people would find that running these tests is not useful, and especially if you find it needing more time than the benefit, then I will gladly support that choice.
Just for kicks I hooked my 121GW up to my 5kV insulation tester yesterday and it survived.
I might do some more testing to see if this can kill other meters.
Don't have a 5kV scope probe to see the waveform though, but assume there will be a small initial energy burst and then clamping down.
Hard to say much about the post. You may have had the meter connected and in the off position for all I know. Maybe the insulation tester was off or set to 500V. Let's assume you actually programmed the insulation tester for 5KV and you connected between the 121GW's V & Com inputs and checked it with the meter set to every mode and it survived. I still have no idea what insulation tester was used. Looking at the Hioki 3455 it looks like it has a short circuit current of 2mA or less. It may be enough to damage the meter but I would expect the 121GW's front end to clamp that down easily, maybe.
Added. You are aware I had changed out the HFE part. This is one of the weak points of the design. If you wanted to try it with the meter set to Hz with the insulation tester putting out a positive voltage on V/Ohm relative to GND, it may do something. You need to somehow get the insulation tester to put out the voltage with an open, get the 5KV then discharge it across the meter. The capacitor that AC couples the grounds together may be enough to exceed the HFE's absolute maximum supply voltage.
A member here, Scott was playing around with electronic fly swatters and actually damaged a meter with one. TI bought one and tried to damage the UT90A with it. The UNI-T UT90A has had more abuse and damaged more times than any meter I have. They flyswatter did not have enough energy to get the job done. The UT90A's clamp would just load it down. So I added a little external capacitance, let it charge, then discharged that into the meter. None of this is useful data and it's not something that is recorded in my spreadsheet.