Date: Sat, 27 Mar 2010 16:02:13 -0800
From: "Zeitler, Lane LT, FST-1" <zeitlel@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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