We've had a page for years now with reviews of various software and simulation design tools, but we've
neglected the hardware and meters part of the business. There's no way to do good design without
good tools -- so on this page we will include reviews of some of the ones we've used with good success.
This article was reprinted from the October 2001 edition of SSS Online.
I finally have an instrument that I have wanted for many years: An LC (inductance
and capacitance) meter. Yes, my digital multimeter (DMM) has a capacitance measuring
function, but it is not really satisfactory for the very-low picofarad capacitors
that one uses every day in RF design. And, of course, the DMM has no capability
of measuring inductance. The HP — no, errrr Agilent, LCR meters are just too
expensive for occasional use.
There are some inexpensive capacitance meters out there that are slightly better
than a DMM but they still cannot measure inductance. As a result, many engineers, and practically
all hobbyists, have not had the luxury of being able to measure inductors. Before
surface mount inductors were the norm, most schematics labeled coils by the number
of turns, the size of wire and the diameter of the form since no one could measure
the beasts!
Well, I recently came across the L/C Model IIB meter made by Almost All Digital
Electronics (AADE) and after using it in the lab for a week I am in love! This meter is
quite inexpensive and simple, but amazingly accurate and useful.
The AADE L/C Meter IIB
It measures capacitors with a resolution of 0.01 pF and inductors with a 1nH
resolution. A simple push of a button cancels out the residual capacitance or
inductance of the test leads and then you are ready to make measurements.
If you make a simple jig out of a small piece of bare copper clad PC board material
you can easily measure surface mount components. I was able to measure 0402 sized
capacitors this way!
The real beauty in this meter, though, is its ability to measure inductors. Just for
fun, I measured a toroidal inductor from a junk computer power supply. The L/C Model
IIB read 5.132 uH. I then removed one turn of wire and measured again. The inductance
was now shown as 3.876 uH. Not only did I measure the inductance of an unknown coil,
but I could also find the permeability of the core.
Another neat function built into the L/C IIB is the "matching" mode. You can
use this mode to make one inductor or capacitor match the value of another one. You read
the value of the first component and then the meter reads the difference between that
value and the value of the second component. This difference is displayed either in
absolute units (pF or uH) or as a percentage.
While this meter is not traceable to NIST standards, AADE claims an average accuracy of 1%
and has test data to prove it. Considering that most components sitting on my bench have 5%
or worse tolerance, this meter can easily classify stray parts into standard values and even
differentiate them within a single standard value.
I have saved the best for the last. This meter is priced at only $129.95 in assembled and
tested form. For you students and hobbyists, a kit version is available for only $99.95, and
the complete instruction manual is available online.
Shipping and handling is a bargain at $4.00 for the US and $10.00 internationally.
Description: The L/C Meter IIB is a hand-held, digital inductance / capacitance
meter with a four digit display, featuring automatic ranging and self-calibration.
Maximum Resolution: 1 nHy / .01 pF
Range: .001 uHy (1 nHy) to 100 mHy (most units measure to 150 mHy)
.010 pf to 1 uF (most units measure to 1.5 uF), with automatic ranging
Accuracy:
1% of reading is typical (Typical means the average error of 83 different components compared to:
HP4275A digital L/C meter (test frequency 1MHz) for components ranging from .1uHy to 1mHy and 2.7pf to .068uF
B&K 878 digital LCR meter (test frequency 1KHz) for components ranging from 1mHy to 100mHy and .1uF to 1.6uF
L/C Meter II is characterized for hobby or non-critical commercial use
Self Calibrating
Error Analysis: 7/18/2000 error analysis against HP 16470A standard Inductor set
Display:
16 character LCD display module
Four digit resolution
Direct display in engineering units (ie: Lx= 1.234 uHy / Cx= 123.4 pF)
jumper option to display pF, nF, uF (ie: 10 nF instead of .01 uF)
Operating modes:
The following modes are sequentially selected
READY MEASUREnMODE - measure Lx or Cx and display in nano units when applicable
READY MEASUREuMODE - measure Lx or Cx and display in micro units (ie: .01000 uF
instead of 10.00 nF)
READY MATCHnMODE -
first measures your reference component Lz or Cz and displays it's value in nano mode
measures subsequent components, Lx or Cx, and displays the difference (Lz-Lx) or (Cz-Cx)
in nano mode
READY MATCHuMODE -
first measures your reference component Lz or Cz and displays it's value in micro mode
measures subsequent components, Lx or Cx, and displays the difference (Lz-Lx) or (Cz-Cx)
in micro mode
READY MATCH%MODE
first measures your reference component Lz or Cz and displays its value in nano units
measures subsequent components, Lx or Cx, and displays the percentage difference
(Lx-Lz)/Lz*100 or
(Cx-Cz)/Cz*100 as percent.
range is -100% to +9999%
maximum resolution is 00.01%
L/C Meter IIB zeros out stray inductance and capacitance by storing their values in RAM
and subtracting them from the measured values. It can zero out any value in it's range
allowing longer test leads and slightly improved accuracy over L/C Meter II.
L/C Meter IIB works by measuring the shift in frequency caused by inserting an unknown
into it's oscillator tank circuit. A PIC16C61 micro-controller measures the frequency
before and after. It then computes the value of the unknown using a floating point math
package and displays the result on a 16 character intelligent LCD display.
L/C Meter IIB will NOT measure inductors designed for 60 or 120 Hz applications such as
power transformers, filter chokes or motors. The minimum test frequency is about 20KHz and
these devices have enormous core losses at that frequency.
