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A bit more on accuracy and tolerance.? Your commercial or homebrewed LC meter

will only be as accurate as its calibration.? Even commercial meters can benefit from

a custom calibration session.? Then it is an issue of how long it will hold this accuracy.

Commercial calibration lab services used to track individual instruments by serial

number and logged the change in adjustments required to bring them back into

calibration.? This provided indication of calibration drift over unit of time so that calibration

offsets could be predicted between calibration dates.

Inductors and capacitors have specific impedances at specific frequencies.? You can

use this to accurately determine the actual value of a capacitor or inductor.? Measurement

can be done with a precision resistive load and RF detector or oscilloscope.?

Another way is to use a bridge network with one leg containing known value precision
resistors and the other leg containing the D.U.T and a precision resistor.? Using the
bridge method does not require a precise frequency...a simple crystal oscillator will
work for the RF source.?

Over the past few years I have slowly converted from leaded components to SMD

types.? Reason is that most SMD components are bulk produced and then laser

trimmed to specific values.? This seems to imply that most, if not all, SMD components

are 1% tolerance, or better.? If the idea of non-leaded components bothers you it is

possible to add leads to SMD devices by holding one end in a metallic (heat absorbing)
vise while soldering a short piece of wire to the opposite end.? SMD components can

also be installed "tombstone style" (standing up on one end) on existing PCB pads

or component leads.? And best of all, SMD components are usually very inexpensive.

Surplus stores sometimes have plastic bags of them for a dollar or so per pound (there

is a lot of SMD components in a pound).? Tweezers type connection probes help to

quickly sort through a bag of random value (floor sweepings) SMD components.

_._

On Sun, Nov 12, 2017 at 11:49 AM, John Kirby <n3aaz_qrp_1@...> wrote:

With respect to several posts here on the discussion group;

I would like to wake up an old (1950s) L C measuring technique where calibration and absolute accuracy was not an issue.

You will need at least two (three is better) reactive components of simular value and quality. We will define one component as our 'standard' and the other as 'unit under test'.
?
Set up...
To measure C ... connect two (2) capacitors in PARALLEL
?> OR <
To measure L ... connect two (2) inductors in SERIES

... if meter allows set to a realistic operating frequency ...

Measure and record the value of two (2) components.
Remove the component 'under test' leaving only the quote 'standard' value connected to the meter.
Record the 'standard' value.
The value of the component under test is the difference between these two measures. Substract the small number from the large number.

I feel the accuracy of this technique is independent of absolute? meter accuracy and as far as I know, there is no way to define the accuracy of the value of the component under test but to say 'empirically' it may be spot on. Remember too component lead length and or stray capacitance of test fixture will play a role in the final 'measured' value.

We used this method long ago when commercial test equipment was not an option for a struggling teenage ham but only had a homebrew grid dip oscillator and general coverage HF receiver. Guess who was king of the ham club when I got a second hand Heathkit GDO?

John
N3AAZ