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On Aug 18, 2022, at 9:51 AM, Pete_G4GJL <g4gjl.uk@...> wrote:

A 1955 Monograph?from the Bell Labs Series.

?Some might find this an interesting background,?else delete.

Pete

G4GJL

On Tue, Aug 16, 2022 at 7:56 AM Dr. David Kirkby, Kirkby Microwave Ltd <drkirkby@...> wrote:

On Tue, 16 Aug 2022 at 01:14, Labguy <georgg@...> wrote:

There is an interesting engineering note from Vishay on the subject of measuring inductance with various pieces of test equipment (including the 4342A) at various frequencies. They quote up to 100% variation in readings on a single test sample (!)

"Frequency Dependance of Inductor Testing and Correlation of Results Between Q Meters and Impedance Meters" (sic)

Google: Vishay 34093

Their conclusion was to stick with the 4342A.

Cheers,

George

VK2KGG

If you are talking about the same document I think you are,

I am not impressed by the methodology in that document?

They have taken a selection of instruments (a Q-meter, inductance meter, LC meter and impedance analyzer), and tested one inductor at specific frequencies (130 kHz, 1 MHz, 10 MHz, 25 MHz and 100 MHz). The measured value varied between 594.0 nH & 1300 nH.? At only one frequency (130 kHz) were two instruments used to measure the same device

Surely it would have been sensible to provide further results.

1) At a frequency at which all the instruments will operate (1 MHz). Then you are comparing apples to apples.

2) Show how the measured inductance changes with frequency on the HP 4342A Q-meter.

Their only real reason for staying they will continue to use the results that would be measured on a HP 4342A Q-meter, is that historically it has been done that way. They even say they will not necessarily use a? HP 4342A Q-meter for the testing.

One interesting? couple of measurements were made using the Tektronix LC130 L&C? meter and the HP 4192A impedance analyzer. The Tektronix LC130 indicated L=1300.0 nH and the HP 4192A impedance analyzer indicated L=607 nH at the same frequency of 130 kHz. That's a pair of measurements taken under similar conditions, but giving very different answers.

An interesting trio of measurements were at 130 kHz, 1 MHz and 10 MHz using 2 different instruments (HP 4192A impedance analyzer and Boonton 62A inductance meter). All 3 answers were within 0.17% of each other, despite the factor of 77 between the different frequencies.

As you say George, the results of the paper and intersting, but I felt the note was rather lacking in substance. I am pretty sure no journal would have published that as a paper, as there's no analysis of the results.

Dave

<Bell Mono _Q_small.pdf>