[Amps] A Means of Measuring Tank Coil Inductance

[Chuck Curran]

To All:

 

I have built amplifier's where I calculated the specific needs for
inductance for the tank circuit.  I then tried several ways to measure what
was then used in the tank coil, simply to verify the results.  I had two
digital meters for measuring LCR components, but the ability to measure
inductance was poor at best, when you looked at a few uH.  I then found a
General Radio 1656 Inductance Bridge and bought it, and quickly discovered
trying to use it at the very limits of its rated inductance range ( 1 uH )
was something that produced less than repeatable results.  I had no
confidence in it.

 

Every couple of months I would search ebay in their used test equipment
area, just to see what else was on the market.  By accident, I then found a
circuit on-line where a fellow used a couple of IC's and a higher measuring
frequency, and then "measured" the inductance  using a frequency counter.
It really looked better than what I had, since it was supposed to measure
down to .1 uH.  I was making plans to build it, however,  I then stumbled
across an add on ebay, for a small unit, possibly similar to the circuit I
found by Googling, but it was more advanced and provide a direct read-out in
uH and Pf.

 

I ordered it and also ordered a bunch of 5% axial lead inductors in the .82
uH to 22 Uh range.  Today this little device arrived from Hong Kong.  I
quickly plugged it in and pulled out the 5 bags of 5% inductors.  It took
about 3-5 minutes to find the proper way of zeroing it out on inductance.  I
then measured each of the 5% inductors.  All five inductors measured within
5% or less of their correct value.  At the moment, I am pleasantly
surprised!  

 

For me this is a real positive step, simply because I enjoy building so much
and I also like to know what the actual component value is, via an actual
measurement.  At this moment I think I can now measure inductance down to
less than 1 uH with reasonable accuracy.  

 

The unit was $39.98 total price with shipping, and took 2 weeks exactly to
arrive.  The component quality and construction appear to be very good.
Lots of people seem to be selling this same unit on ebay, here is a link to
the source I got mine from, if you have a need or interest:

 

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem
<http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=150504831155&ssPageName=
STRK:MEWNX:IT#ht_6248wt_1139>
&item=150504831155&ssPageName=STRK:MEWNX:IT#ht_6248wt_1139

 

I hope this helps a few of you,

 

Chuck  W9POU