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Microamps and Millivolts Measurements on UT61E
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bdunham7:

--- Quote from: coromonadalix on December 08, 2022, 12:48:15 pm ---Once again at theses values  the uni-t meter will round them sometimes, IT IS not made for these low currents values

you are using cheap meters to do extensive work / measurements,  it kinda become stupid in a sense

--- End quote ---

I don't think the quality of the meter is all that relevant here and I don't think a 'better' meter is going to behave differently enough to matter much.
Kleinstein:
The reistance is likely the smaller problem here. Mesuring the PWM signal causing likely internal clamping is likely the larger problem. Ideally a meter would catch that, but not many meters do that. With the larder rage there is enough headroom to accect the signal, but not with the smaller ranges. Even good meters will fail on this.

For the books it is really hard to tell. The right book depends on the person to read it. To simple / low level makes it boring to read and likely missing out on parts. Too difficult / mathematical just causes frustration.
JenniferG:
The PWM's duty cycle being an issue makes sense, especially at very low duty cycles like I did with the voltage reading I shared here.  I can understand.  I don't understand how the meter integrates or whatever.. but I do understand Integration with respect to calculus.   It makes sense that the samples might not be small enough or whatever, to catch the duty cycle.

If I wanted to measure the actual voltage, would it help to put an electrolytic cap in parallel to hold the PWM's average charge, or whatever.. I really am clueless lol.
bdunham7:

--- Quote from: JenniferG on December 08, 2022, 03:10:28 pm ---What order should I read them?  Which should I skip?  I have the Art of Electronics and it's too overwhelming for a beginner I think.

--- End quote ---

AoE is way too advanced for where you are at.  It might be interesting because it is full of practical working examples, but it assumes a certain level of theoretical knowledge.

You can read Wayne Storr's free online basic tutorial (it goes quickly, but concentrate on a page per day or so--don't whiz through it).  Also study Thevenin's theorem thoroughly, along with Norton's (linked in the Wikipedia page)

http://www.energiazero.org/elettrotecnica/basic-electronics-tutorials.pdf

https://en.wikipedia.org/wiki/Th%C3%A9venin's_theorem
mqsaharan:
Hi JenniferG,
You are right the difference shouldn't be this much in measurements within the different ranges of the same instrument but in your case it appears so. That is why bdunham7 has suggested to put both of your meters in series while measuring the current. When you'll change range on 61E from mA to uA, the other meter will verify if your 61E has any problem/fault or not. Also, please keep in mind that this meter is geared towards hobbyists not professionals so less attention has given in its design to keep things agreeable within the instrument.

Sadly, manufacturers has stopped including detailed operating instructions in the manuals. I guess it makes their instruments appear less attractive.
I am attaching here three pages from Fluke 8020A multimeter's user manual (https://dam-assets.fluke.com/s3fs-public/8020A___imeng0000.pdf) that'll hopefully explain you why you are getting such a big difference between mA and uA current ranges within the same instrument. Also, attached here is the schematic of UT61E. You can see that this meter uses 1k for the lowest range in uA position and 10 ohms in mA range. Please do watch Joeqsmith's video in reply #12 regarding burden voltage of this meter.

If you want lowest error in current measurements you can get a meter that has lowest burden voltage. The cheapest meter I know that has lowest value shunts thus have lowest burden voltage is UT61D. It is using 50 ohms (uA range), *0.5 ohms (mA range) and 5 milliohms (A range) resistors as shunts.

Edit: *0.5 ohms current shunt for mA range.
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