How Are "Henries" Measured?

[Als Kimp Tones]

Hello, I'm new. It seems that henries are an important spec for pups. What does it take to measure? Thanks

[Rob S]

I use the inductance setting on my multimeter but as an aside, I got nearly 1.25 million hits when I googled 'Inductance Measurement' as compared to over 35 million for "Troll".

Rob.

[Magnetosaure]

Hi,

First post for me too...

I think that most of the pickups manufacturers indicate the inductance of their pickups measured with a test frequencie of 1 KHz. The measurement change if you use a different frequencie.

I'm I right?

[soundmasterg]

What you want to do is to get the Extech meter that just about everyone uses. It is model 380493 I think. I'm not at home right now so I can't look at it and say thats it for sure or not. Maybe someone else who has one can confirm if I have the number right or not. They're under $200, and can measure inductance, Q, and AC resistance at 1 Khz and 120 Hz in series or in parallel. Most people seem to use the 1 Khz setting. They're quite accurate and easy to use, and will give you some real useful info about the pickups. You can use high AC resistance numbers in relation to the DC resistance number to tell if you have a shorted coil for instance.

When measuring any of those, the reading does change with frequency, and also with temperature. So if you measure in your garage on a cold day, you will get lower numbers than if you measure on a hot day.

[Ray Ivers]

Apex Jr. has a Victor VC6243 LCR meter for $50! which I found after paying about $170 for my B&K...

Ray

[Als Kimp Tones]

Hey, thanks everyone.I think I now know what direction i need to go.Winding pickups isn't rocket science,but it sure is science.

[soundmasterg]

Ray how accurate is that one you got at Apex Jr? And does it test as many things as the Extech? Everyone here seems to use the Extech, and I've found out that companies like Rickenbacker use it too. I like my Extech a lot as its really easy to use, very flexible, and isn't priced too badly.

The hard part is equating the science of pickup making to actual real world things. You can have all the inductance, Q, and AC resistance specs in the world, but if you don't know what those numbers mean in relation to a pickup, then it doesn't do you any good.

[Ray Ivers]

Greg,

I really didn't accuracy-check it at all - in fact, my buddy Scott was over and I gave it to him as a gift; I waited far too long to get my first cap checker (and 22 years for an LCR meter!) and I didn't want him to do the same thing.

Equating the science to the sound IMO requires a "bridge" - for many this is experimentation and empirical methods combined with measurements, for me it's all of these things plus math (mainly to compute gain and L/C/LC/RC/etc. filter behavior - I let the computer handle this part, believe me), for others it may be purely theoretical and mathematical using measurements only for confirmation before listening tests begin, I don't know. So far I've only used my LCR meter to check capacitor values and OT primary inductance, but I know I'll use it more as I get used to having it around.

Ray

[Dave Kerr]

Ray how accurate is that one you got at Apex Jr? And does it test as many things as the Extech? Everyone here seems to use the Extech, and I've found out that companies like Rickenbacker use it too. I like my Extech a lot as its really easy to use, very flexible, and isn't priced too badly.

The hard part is equating the science of pickup making to actual real world things. You can have all the inductance, Q, and AC resistance specs in the world, but if you don't know what those numbers mean in relation to a pickup, then it doesn't do you any good.

According to this Yahoo store, the specs:
# CAP: 0 - 2n - 20n - 200n - 2u - 20u - 200u - 1000uF
# Inductance: 0 - 2m - 20m - 200m - 2H - 20H
# Capacitance accuracy 23°C +/- 2°C: < 0.5Uf +/- 1.0%, > 0.5uF +/- 2.0%
# Inductance accuracy 23°C +/- 2°C: < 0.5uH +/- 2.0%, > 0.5uH +/- 5.0%
# C Temperature coefficient: < 0.5uF +/- 0.1% /C, > 0.5uF +/- 0.2% /C
# L Temperature coefficient: < 0.5H +/- 0.2% /C, > 0.5H +/- 0.5% /C
# Zero Error: C < 5pF, L > 10uH
# Size: (inches) 3.8 x 8 x 1.6
# Weight: (Lbs) 1.37

[soundmasterg]

Those specs don't say anything about what frequencies it tests at as far as the inductance. It would be helpful to know that if someone was going to use it for pickups, since they are usually pretty high frequency compared to what the meters test at.

Ray, how do you use the LCR meter to check the OT primary inductance? That would be useful for me to know how to do. I'm sure I could use my Extech for that if you've been using that one you had.

Greg

[Ray Ivers]

Greg,

Ray, how do you use the LCR meter to check the OT primary inductance? That would be useful for me to know how to do. I'm sure I could use my Extech for that if you've been using that one you had.

My exact method? OK, well, first I measured a 20H OEI choke - 20.0H, great. Then I connected it across the OT primary with secondaries disconnected - no reading at all (IMO it's important to include this step to fully "learn the lesson", so to speak ). Then, it was pointed out to me that that wouldn't work so I shorted the secondary, measured it again, and got my reading. In retrospect, I suppose loading the secondary with the proper load resistance would have given the most accurate reading, but the one I got was ballpark correct so I didn't try that (I will from now on, though).

FWIW, so far I really don't like the B&K 875B at all, although I didn't compare it to the one I gave away (I'm thinking I should have given this one away instead ). It seems very reluctant to give readings, and just kind of finicky in general, a far cry from my Fluke 87 DMM which just plain gives me what I ask for, every time.

Ray

[soundmasterg]

Thanks Ray! I'll have to try my Extech and see if I can get a decent reading on some OT's. I've got a B & K DMM, but I can't recall which model. It works fine for me.

[Rob S]

You may be interested in what R.G. Keen has to say here:

http://www.geofex.com/Article_Folder...es/xformer.htm

- particularly the terminology part at the top

[David Schwab]

My method is to tell Henry to stand against the wall, make a mark with a pencil and get my tape measure...

OK... ok... it's Friday... everyone have a great weekend!

[Rob S]

My method is to tell Henry to stand against the wall, make a mark with a pencil and get my tape measure...

OK... ok... it's Friday... everyone have a great weekend!

I think it's saturday and I feel just like you did there