On 7/9/19 5:02 AM, Look165 wrote:

Phil Hobbs a écrit le 09/07/2019 Ã* 00:16Â*:
On 7/8/19 2:04 PM, Look165 wrote:
I got a problem measuring efficienty on an SMPS unit.

The meter I used was indicating about 50% which was absurd.
I brought my personal old analog meter, it said about 85% !
That's why I don't like todays's meters.

You can get a true-RMS meter for way under $50.

NO ; with today's DMM the value is only true with sine wave.
Some use triangular signal, other Dirac comb.
They sample the signal and then computation and mathematical process.
The older one (AMM) were making true measurement with a rectifier and a
filtering cap.

This is particularly obvious in Amperemeter operations.


You're cracked. (Plus you top-post.)

Rectifier + filter is _not_ a true-RMS meter.

https://www.walmart.com/search/?cat_id=0&query=true+rms+multimeter

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com