Also now I wonder what do those specs mean?
Also now I wonder what do those specs mean?
I explain about multimeter specifications here: https://lygte-info.dk/info/DMMTolerances%20UK.html
Usual they are only valid between 18°C to 28°C, for each degree outside you must add some more tolerance.
So, then for the Brymen 869s in the video, specs for the 500.00mV range is:
DC Voltage, 869s, 500.00mV, 5.0000V, 0.02% + 2d
And since this spec is for 50,000 count range, I think I need to drop the last digit from the 500,000 count readings shown in the video (is this correct?).
Since Joe is measuring 1.00mV (assumed), according to the spec, readings should be:
1.00mV x 0.02% = 0.0002mV, and add 2 counts of 0.01mV and you get 0.0202mV, or for the meter 0.02mV.
So to meet specs, the meter needs to show something between 1.020mv and 0.980mV... is this right?
Thanks for the tests provided. Did one of the meters have become drifted after the test, for example the owon B41?
Yes, but again only in a limited temperature range, Joe goes well outside that range.
Thanks for the tests provided. Did one of the meters have become drifted after the test, for example the owon B41?
They all returned to normal after a day.
Yes, but again only in a limited temperature range, Joe goes well outside that range.
Yes I understand that... and yet the meter stayed in-spec regardless of the out-of-spec temperature (and condensation) condition, which is impressive. I wonder if Flukes do as well... I'm guessing probably the industrial ones will (or maybe all?).
Ohh crap was the leads or input jacks ? Or is the default error message for anything bad ?
It did seem to fall out of the 20 count spec for some duration... I'm guessing due to the condensation? I wonder what parts are affected by it... I'm guessing an analog part like the PTC? Or more generally some current leak on the board in the analog input section. I bet some insulating coating on the board can eliminate the condensation effect.
Keep in mind that during the transition, all of the components may not track. That difference can cause a fair amount of error and is why the meter is allowed to stabilize for a half hour. There is a fair amount of air movement but even a half hour may not be enough to some of the meters to settle.
Put two thermometers outside, one in a glass of water the other in open air. One will respond slower. This delay can cause a fair bit of error and again is why I let them settle.
In the mV range the input impedance of a crap meter is a Meg. The PTC is about 1.5K. Say the PTC changes 100%. What's the total error it causes?
Old Fluke 189
So in your opinion, do you think the error is caused more by uneven temperatures of the components, and less by condensation's effects on the board?
When it comes to trying to solve problems, I find my opinions mean very little and data is pretty much everything.
There are a few easy experiments that could be ran if we needed to sort it out. The UT61E for example, drifted far worse. It may have been the worse I have seen. For less than the price of a coffee, I was able to tame it. Then again, I wasn't considering my time having a cost. If I did, the UT61E I have is worth a bit more than a standard one...
It's good to know that the TOC was a waste of time.
It's good to know that the TOC was a waste of time.
You'd mentioned this in many of your videos (also listed on post #1), so I guess it's an unbending rule .
...A few good articles if you are interested:
http://www.grainger.com/content/safety-digital-multimeter
http://cp.literature.agilent.com/litweb/pdf/5990-4578EN.pdf
http://faculty.riohondo.edu/jfrala/fluke_multimeters_-_abcs_of_multimeter_safety_multimeter_safety_and_you_application_note.pdf