Fewyears ago I made a microcontroller SMPS project.
But it did not work first.

A colleague helped me find out for the mistake. We had something like this:

- Let's measure if the microcontroller out PWM!
- So how to measure with this PWM?
- Is 0...5V ?
- Yes
- The device shows 2.5V so we had PWM with Duty Cycle 50% because the pin can not have an analog value.
-.........................................

I'm waiting for your other tips suggestions.

 

An oscilloscope would be best. You could try interval measurement with a frequency counter.

DMMs cannot measure square waves and probably don't work for anything other than sinewaves near line frequency.

 

...plus, DMM's (el-cheapo's) have trouble sensing higher frequencies.

 

I have a FeelTech wave generator, a VC99 meter and an old analog scope.

I paid less than 40 bucks for that meter, new on ebay. I can measure a 5 volt P to P.... from DC to 15 MHz square wave dead on., with the frequency function.

I can measure a sine wave up to about 25 MHz.

Great meter. Great generator too.....even has a stored heartbeat.

 

few DMM's that I seen will have trouble measuring proper voltages above few hundred Hz..
BR-549, I stand corrected..

 

few DMM's that I seen will have trouble measuring proper voltages above few hundred Hz..
BR-549, I stand corrected..

If you are referring to the AC range then yes it is made to measure 50Hz.
the limit of 1N4007 is about 500Hz.

I measure the peak value of "alternative" voltage putting in series a fast diode and the DMM on voltmeter.

 

The low pass filter in the DVM averages the PWM value similar to the low pass filters we commonly use in PWM DAC applications.

Another "trick" is to make a peak detector so you can use the DMM to measure peak voltages, such as those appearing in switching power supply circuits.


To measure small changes in voltages that are higher than the most sensitive scale on the meter, connect one side of the meter to a voltage reference then you can see small changes. I used this approach to check the monotonicity of a 5V 12 bit DAC.

 

Or very small resistance with Wheatstone bridge:
https://en.wikipedia.org/wiki/Wheatstone_bridge
E.g. 0.33 ohms for AB audio amplifier.

Theoreticaly you can do that in AC to measure small L an C.

If you buy a 10 000uF capacitor and want to measure real C, charge them at known voltage value and measure time of discharge through R=10K with Voltmeter connected

If you have a good filter on output of RF amplifier you can estimate output power with an incandescent small light bulb.
The same with a fast dioda you can create a reflectometer???????????????

 

I'll use an Arduino Nano to devise special purpose test devices. For example, I needed to test several large value electrolytic caps the other day. My DMM could not handle them so I wrote a little program that used the ADC to measure the RC time constant with a known resistor (0.01%) and unknown capacitor (DUT). From that I could calculate the capacitance. Turned out to be pretty good for my needs and I did find the bad cap I was looking for.

 

If you buy a 10 000uF capacitor and want to measure real C, charge them at known voltage value and measure time of discharge through R=10K with Voltmeter connected

That might take a while. Charging to 5V would take 1:40 to drop to 1.84V (RC discharge level). 1K would take 10 seconds.

 

An oscilloscope would be best. You could try interval measurement with a frequency counter.

DMMs cannot measure square waves and probably don't work for anything other than sinewaves near line frequency.

My Tektronix DMM252 has a setting for Hz. Not sure what it's actually measuring but it did read accurately on a couple projects where I knew the answer. $38 from my local flea market, highest price thing I ever bought there.

 

My Tektronix DMM252 has a setting for Hz. Not sure what it's actually measuring but it did read accurately on a couple projects where I knew the answer.

It has been my experience that on AC settings, meters expect sinewaves near line frequency.

Full disclosure: I do not have exhaustive information on *all* multimeters and my comments are of a general nature. Could there be exceptions to my statement? Of course. Would typical hobbyist type meters have that capability? Not likely.