Multimeter can't do AC Current measurement?

[Maxcot]

A real simple question... I'm trying to measure an AC current in the region of 8A. My multimeter is a Major-Tech MT845 - quite old, digital. It has DCV, ACV, DCA, Ohms settings on the dial but no ACA (AC Amps?). I gather I cannot use it then for my purpose?

 

[tpetar]

Send us picture of multimeter. With this description it cant.

 

[Maxcot]

Cheers.

 

[tpetar]

Only DC amperage, no capability for measuring of AC current.

 

[yadavvlsi]

Basic indicator system in either an analog or digital meter responds to DC only, a multimeter includes an AC to DC conversion circuit for making alternating current measurements. Basic meters utilize a rectifier circuit to measure the average or peak absolute value of the voltage, but are calibrated to show the calculated root mean square (RMS) value for a sinusoidal waveform; this will give correct readings for alternating current as used in power distribution. User guides for some such meters give correction factors for some simple non-sinusoidal waveforms, to allow the correct root mean square (RMS) equivalent value to be calculated. More expensive multimeters include an AC to DC converter that measures the true RMS value of the waveform within certain limits; the user manual for the meter may indicate the limits of the crest factor and frequency for which the meter calibration is valid. RMS sensing is necessary for measurements on non-sinusoidal periodic waveforms, such as found in audio signals and variable-frequency drives.

https://en.wikipedia.org/wiki/Multimeter

 

[Maxcot]

Could anyone suggest a suitable meter that will? Looking for basic AC and DC Voltage and Current measurement, with max of 600V / 10A. Any other features a bonus. Obviously the $1,000 dollar version does, but I'm on a budget.

 

[tpetar]

All new multimeter support AC / DC current and voltage, even low budget instruments.

 

[Maxcot]

All new multimeter support AC / DC current and voltage, even low budget instruments.

Not sure if I agree... the price difference between a multimeter that will not measure AC current, and one that will measure 10AC is about 100% - one is double the other. Alternatively I could get myself a clamp on type to use for the current measurements. I'm offered a MT87 at a really cheap price. It looks like a Chinese manufactured product, and I have no idea about it's long term robustness or accuracy. The fluke will cost several hundred dollars, this mt87 less than $50.

 

[tpetar]

Measuring AC current :

Older multimeter uses a diode, capacitor, and resistor to measure the peak to peak voltage of the AC signal. They then compensate their calibration to read in a close approximation of what the RMS value will be. Problem is that this only works well for true sinusoidal waveforms - if the wavform is triangular, for instance, the indicated value will not match the RMS value.

The newer style meter, if it states that it is a true RMS meter, will sample the input waveform and actually calculate the RMS value. This is done by adding up the squares of the input, and then taking the square root of the result. That is a much better approximation of how much power the waveform can deliver.



I'm pretty sure if Fluke sell ordinary pen that price will not be under 100usd or 100eur.

---------- Post added at 09:48 ---------- Previous post was at 09:42 ----------

See MASTECH company products.

---------- Post added at 09:50 ---------- Previous post was at 09:48 ----------

http://www.mastech-hy.com/index.html

---------- Post added at 09:54 ---------- Previous post was at 09:50 ----------

Example :

Multimetar Mastech MS8221A

Price in Serbia 22eur

http://www.mikroprinc.com/proizvodi...-mastech/multimetar-mastech-ms8221a/index.php

---------- Post added at 09:57 ---------- Previous post was at 09:54 ----------

Real price is 65%-70% of that price.

---------- Post added at 09:59 ---------- Previous post was at 09:57 ----------

There are also cheaper models but I dont have will to search.

 

[Maxcot]

Thank you very much, that is very helpful. I have found some Mastech products here for about US$25. Much appreciated.

 

[mister_rf]

Try to buy a DMMs built in "auto-range" features that will automatically select the proper range. The auto-ranging scales eliminate the need to dial in the correct range when making electronic measurements…

 

[tpetar]

Thank you very much, that is very helpful. I have found some Mastech products here for about US$25. Much appreciated.

I told You. There is even cheaper, I think for about 15eur nice instrument. Semi pro 40-50eur.

But we must speak this prices very very quiet that fluke not hear. :smile: