phase difference measurement

EDAboard.com Forum Index -> Robotics and Automatics Forum -> phase difference measurement

Author

Message

b.zahedi

Joined: 20 May 2008
Posts: 18

26 May 2008 7:06 phase difference measurement

I want to measure phase difference between two currents through a low cost method, It doesn't need to be very precise. What do u suggest me ?

Tnx,

echo47

Joined: 07 Apr 2002
Posts: 4206
Helped: 566

26 May 2008 8:22 phase difference measurement

Tell us more about the amplitude and frequency of the currents, and your definitions of "low cost" and "not very precise".

Google
AdSense
Google Adsense

26 May 2008 8:22 Ads

b.zahedi

Joined: 20 May 2008
Posts: 18

27 May 2008 10:04 phase difference measurement

ok, my question was too general,
frequency is between 20 and 60 Hz, and amplitude is about 5A and less, the signal is very noisy, because of using inverter.

I don't want to use CTs like LA25, because i don't need this much precision and it costs much. I'd like to use a simple method...

FvM

Joined: 22 Jan 2008
Posts: 5160
Helped: 767
Location: Bochum, Germany

27 May 2008 13:08 Re: phase difference measurement

If you don't need to measure below a 10 or 20 Hz, you can use simple current transformers instead of LEM transducer. The transformer should be terminated at best with a zero input impedance current amplifier and the specification checked for an accepatable phase error at minimal frequency.

For the measurement circuit, different solutions are possible, low pass filtering, zero crossing detector and digtal timing measurement is proably most simple. I expect that the inverter current waveform has no low order harmonics, so a simple low pass should be sufficient, otherwise a tuned filter may be necessary.