[Amps] LCR meter

[Jim Thomson]

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