[Amps] LCR meter

[Jack/W6NF]

I have used an HP LCR meter at work but never paid any attention to the
frequency at which the measurement is made. I wonder what discrepancies in
measurement values of L and C could be encountered if one measured at
various RF frequencies, and why they might occur. I have seen such
discrepancies, using a popular antenna analyzer, even though I was careful
not to introduce sources of error, like lead lengths.

Thanks,


On Tue, Mar 30, 2010 at 3:58 AM, Jim Thomson <Jim.thom at telus.net> wrote:

> Date: Sat, 27 Mar 2010 16:02:13 -0800
> From: "Zeitler, Lane LT, FST-1" <zeitlel at cpr3.navy.mil>
> Subject: [Amps] L and C "meter"
>
> I am curious as to what you guys are using to measure the L and C of
> your circuits/components. I looked at the B & K 875-B and it can be had
> for $192.00 on Amazon dot com. I do not know if this is reasonable but
> the meter seems to offer quite a bit and the accuracy according to the
> specs seems pretty good.
>
>
>
> Lane
>
> Ku7i
>
> ##  I bought a new  B+k 875-A  back in 1992.  Still  works superb.
> ## last year, I bought a new 875-B. Both units  are an industry
> standard, and just don't crap out.   The 875-B comes with a
> 3 yr warranty.  They both use  1 khz  square wave for the measurement
> freq.
>
> ## The newer 875-B  will measure  lytics up to  20,000 uf. [875-A will
> only measure up to 2000 uf]    875-A measures DC resistance.  The
> 875-B measures AC resistance.. and now has a 2 ohm scale.. and measures
> down to .001 ohm.   Both of em will measure  down to .1uh  and .1pf
>
> ##  Both will measure  uh  up to  200 Henries !    We have used the 875's
> at work for measuring huge chokes, etc.   The 875-B  has a front panel
> adjustable  zero set.. which is a big bonus.  The older 875-A  didn't...
> and I always
> had to remember  to subtract .66 uh  for the  2 x 12"  long test leads.
> The B
> model comes with  2 x  6"  test leads.
>
> ## The  AS   Aim  4170 is even better, but requires a PC.
>
> ##  Bottom line is, I require  something that will  accurately  [1%]
> measure typ stuff
> ,like a 2.2 uh  tank coil, or measure the stray C  of cab side walls  [typ
> 1-2 pf] ,
> big and small chokes, and also audio chokes and xfmr's.  The 875-B  will
> also measure
> the ESR  on HV lytics..down to .001 ohm.    You can spot a bad cap asap.
> Both will also measure D on caps.
> Being able to now measure up to 20,000 uf  [ instead of 2000 uf]  is a big
> bonus these days.
> All my hv lytics  are >  2000 uf.    B4  I had  to put 2 x in series.
>
> ## the real bottom line is.. with out some kind of lcr meter, or similar
> device, you are dead
> in the water, when playing with amps.   A  YC-156 has 35 pf C.. between
> anode and grid flange
> on the wooden test bench.. which rises to aprx 53 pf.. when bolted to
> chassis.   A  3CX-3000A7
> is 24 pf.. and rises to 33 pf, when inserted into socket and grid ring.   A
>  YU-148 is 24.5 pf.... and
> rises to 39.6 pf  when  installed in socket.
>
> Think abt it.  For amps,[ and ham radio in general].. all you are playing
> with is pf and uh.....
> and stray pf and stray uh.  Not having a LCR meter is like not owning a
> screw driver !
>  It's the number 1 tool.   Want to know how long that coil of  213 is ?
> Just measure the C  between
>  braid and center conductor... then divide by XXX .
> I measure all the C  on control cables, coax etc.. and document it.  Very
> useful  when it comes to
> trbl shooting.   We  started using lcr meters a few yrs ago on new ADSL
>  equipment /turn ups
> in the local telco I worked at.   Once C readings  were taken on known
>  good cable assy's, and esp
> pot's  splitter/filter assys...  finding a bad one was real easy. Get  2 x
> rings crossed.. or 2 x tips crossed
> in a factory splice, or a contractor splice..and the  C readings instantly
> change.. dead give away.
>
> Later...... Jim  VE7RF
>
>
> F
>
>
>
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-- 
Jack, W6NF
Silver Springs, NV
DM09ji