Hi

If you try to do Current measurement on a square wave, in order to find the current in the "1" part of the wave,
most multimeters will not give you that info, when you set them on Current measurement mode.
You will probably get some effective value, instead of the value at the peak of the wave.

Can anyone please recommend me a multimeter that can do it?

For example,
If you have an IR Remote Control for some device (TV, TV Box, Audio System, etc),
and you want to know the current going thru the IR LED.. which receives a square wave.

Thank you

 

The Fluke 87V has a peak MIN/MAX setting.

 

Thank you very much nsaspook.

Fluke's Multimeters are quite expensive,
maybe you know one that is not by Fluke, and should do it too?

 

It looks like there are at least 2 options:
1) The Fluke at $300+
2) An oscilloscope for <= $300

https://www.amazon.com/Fluke-FLUKE-...rds=fluke+87v&qid=1555191001&s=gateway&sr=8-2
https://www.google.com/search?q=Osc...ome..69i57.13959j1j7&sourceid=chrome&ie=UTF-8

What precision do you need? My choice with a limited budget would be an inexpensive oscilloscope. That is, unless it was to be a single-purpose instrument.

 

Whats the freq of the square wave ? Do you need instrument to be portable of
can it be PC based ?

https://www.ebay.com/itm/Promo-iCP1...702947?hash=item1ccf1a7923:g:mfUAAOSwys5WUMMB

Regards, Dana.

 

Thank you both.

If taking the example of an IR Remote Control, then we're talking about 38KHz..
The USB Adapter will not be good since it's samples at 1ms intervals.

 

DSO112A, < $50 on ebay, will do this.

https://www.ebay.com/itm/DSO112A-Ha...hash=item3fa48118d1:m:m1K-Ixpx4FTQH7VNcTNHYiw


Regards, Dana.

 

If you can program just a few lines of code and this will
handle using onboard SAR and UART to PC Terminal
program. $ 10. This will do > 500K SPS.

Tool, Compiler free.

https://www.cypress.com/documentati...s/cy8ckit-043-psoc-4-m-series-prototyping-kit


Regards, Dana.

 

Thank you.

BTW, in general, a Multimeter that has a Min/MAX feature should do the job?

I should just set it to Current measurement, choose "Max",
and then measure the current when a wave is passing, and then get the value of the "1"?

 

in general, a Multimeter that has a Min/MAX feature should do the job?

If it has the frequency response you need (as stated in its specifications), yes.

 

Measurements like this are usually dependent on "crest factor".

The current ranges on most multimeters are just resistors. This may be troublesome without an I-V converter.

Frequency response is another issue.

 

I see.

I have my eyes on Uni-T - UT139C.

It looks like a nice Multuimeter, it has the Min-Max feature,
and it's priced reasonably.. (even more than reasonably) - it's around 40$.

Will it's Min-Max feature be relevant for a 38KHz wave?

Here's its product page:
http://www.uni-trend.com/html/product/General_Meters/Digital_Multimeters/UT139/UT139C.html

Its manual is under the "Docs & Software" tab,
I downloaded it but couldn't see any mentioning for a Frequency regarding Min-Max.

Maybe you know how can I find this info - if this Multimeter is relevant for what I need?

 

Zohar, I have never seen a multimeter designed to measure square waves. danadak has the solution....a pocket scope.

 

I'd just use the poor man's version: Measure the current with a cheap meter and multiply by two. You did say it's a square wave. I believe a cheap meter simply reads the time-averaged current. If you didn't really mean square wave and instead have some sort of PWM, that's different. You could set the PWM to 100% and measure the peak current directly.

 

It's an IR Transmission..
o definitely not a square wave that we know its duty-cycle and can calculate anything about it.

OK, I will use a scope..

 

Here are the footnotes to the AC Current measurement for that meter:



That is on pages 20-21 f the user's manual. I am not sure min/max has the same meaning as peak to peak for all meters. It can mean, the minimum and maximum voltages over a fairly long period, as is often needed in measuring temperature.

 

Thank you very much jpanhalt.

OK in that case a Multimeter will not help

Scope then.

Thank you all