Measuring inductors

[hodad]

I have one of those cheap LCR/Transistor testers (like this: tester), and when checking inductance across one side of a transformer I get a different reading depending on which pair of the 3 connections on the meter I use. As a f'rinstance, I'll see 2.4 Henries if I'm hooked to 1 & 2, but 3.8 across connections 2 & 3. I'm a little befuddled as to what would cause this difference. The meter, considering its cheapness, has proven pretty useful in other situations, and I can't quite figure out why I'm seeing what I'm seeing here.

 

[emrr]

Is it series / parallel?

 

[gyraf]

To figure out what terminals are closest to the truth, put a known-value capacitor in series and measure resonant frequency..

 

[CJ]

What kind of transformer are you trying to measure?

 

[hodad]

What kind of transformer are you trying to measure?

Just a crappy little 600:600 OEP. I've also tried with another small isolation transformer of unknown origin with similar results. Measuring across either primary or secondary produces similar results. I'll probable just build a couple of simple filter circuits & see which value seems best reflected by the behavior I see.

 

[CJ]

How come they have 3 leads on the tester?

 

[Gold]

How come they have 3 leads on the tester?

It does transistors too. It's a very handy little tester. You can also get them in a small case with an Li battery for more like $18.

 

[dai h.]

(I think) those are from this open source project:

https://www.mikrocontroller.net/articles/AVR_Transistortester

FWIW (instructions on measuring coils) is on page 45 "section 3.10 Measurement of coils"

https://www.mikrocontroller.net/articles/AVR_Transistortester#Downloads_(English)