Multimeter AC Hz testing

Thread Starter

Mr. Multimeter

Joined Sep 17, 2018
66
Need to verify the frequency range in ac volts that my friends old multimeter is capable of measuring...any thoughts on the best way to do this? He wants to use his dmm for some audio projects. I think he needs 14-20 kHz accuracy.
 

wayneh

Joined Sep 9, 2010
17,027
Use a smartphone app to generate the tones. Tap into the signal coming out the headphone jack for measurement by the DMM. I believe the smartphone will have a wider range than 14-20K but you may want to look it up. The low end you want might be a bit low for it.
 

Papabravo

Joined Feb 24, 2006
15,464
What does the documentation that came with the meter have to say on the subject? It might be as low a 1KHz. I've never seen an audio technician use a multimeter for AC measurements except in the power supply.
 

dl324

Joined Mar 30, 2015
12,677
Need to verify the frequency range in ac volts that my friends old multimeter is capable of measuring...any thoughts on the best way to do this? I think he needs 14-20 kHz accuracy.
Read the manual. I was surprised that my old Fluke 8010A will measure AC up to 50kHz and my HP 3438A will measure up to 100kHz.
He wants to use his dmm for some audio projects.
I'm not certain how useful an RMS voltage reading would be. An oscilloscope would be a better tool.
 

DickCappels

Joined Aug 21, 2008
7,155
If he AC couples the signal and then peak detects it (with bleeder) he will get the peak voltage minus one diode drop. This can be read with voltmeter on a DC scale.

Another solution is to make an AC RMS too DC adapter with something like the LTC1968, which is very good for this kind of measurement.
1615133732577.png

The trick then becomes that of coming up with a suitable signal source.
 

Thread Starter

Mr. Multimeter

Joined Sep 17, 2018
66
Wow..great info everyone..I really appreciate the feedback on this. Seems like I may have opened Pandoras box on this one.BTW, there was no manual with the multimeter. It's a Mastech M3900.
 

Papabravo

Joined Feb 24, 2006
15,464
Wow..great info everyone..I really appreciate the feedback on this. Seems like I may have opened Pandoras box on this one.BTW, there was no manual with the multimeter. It's a Mastech M3900.
Oh ye of little industry. Manuals are online for just about everything. Check out page #6

https://www.manualslib.com/manual/1319650/Mastech-M3900.html?page=6#manual

Frequency range is 40 Hz to 1 kHz. Average RMS of sine wave.
This will definitely not be of any conceivable use in audio work except for measuring the power supply.
 
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