Where is the link?

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>

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>

https://www.rsp-italy.it/Electronics/Magazines/index.htm

?

With all the talk of ‘Q’ meters and CMM’s, those interested might like to take a look here…

?

?

John’s excellent pages give some incite into the quality of the UK made products of the time…

?

Regards

Nigel Adams – Marconi Instruments Heritage Collection.

?

?

On Sun, Aug 14, 2022 at 08:31 AM, Chuck Moore wrote:

The question was asked previously why the thermcouple heads
in the Boonton Q Meters were so fragile and prone to burnout
so easily.

<snip>

If you look at:

That's Brooke Clarke, who is a member of this list.

<snip>

Back to the Q Meter.

The thermocouple is heated by a short length of what is reported
to be nichrome wire. The writer at prc68 reports the wire is 37
gauge or 0.0045" in diameter. The nichrome wire heater and the
thermocouple both are mounted on the bakelight disc inside the
sensor head. and the thermocouple bead is welded to the heater
wire.

In looking at a chart which showed various nichrome wire gauges
and the expected temperature of the wire when a specified current
flows through the wire, 37 gauge Nichrome A wire would reach 1600
degrees F for 1000 milliAmps flowing through the wire.

Looking at the chart found here:



you can see a fairly wide range of temperatures for currents varying
from 350 milliAmps (400 degrees) to 1290 milliAmps (2000 degrees F).
The reported melting point for Nichrome A wire is 2,552 degrees F. The
current to reach 2000 degrees is only 29% over the current reported to
be flowing in the precision resistor in the Q Meter.

Ah, so the sense wire gets very hot. I assume that means ambient temperature changes are no so significant, as it's so far above ambient.

I thought I read in the 260-A manual that the RF signal generator only run at 50% of the power that could destroy the thermocouple, implying this would not happen like it did in the 160-A
But maybe I got that wrong.

If you examine the
scale of Boonton 260's Multiply Meter which is monitoring the current
through the nichrome wire, the meter is marked with a red zone that
begins at about 5% of the meter scale above the meter scale's "Multiply
by 1" mark. It appears that the heater operates at a temperature that is
was approaching 63% of the wire's melting point.

Em, I like to design things with a bit more to spare than that!

Peter Olin, AI2V (reported to be a silent key) at one time provided repairs
and conversions of the 260 Q meter to include sensor head repairs. I also
remember that one conversion of the unit led to the vacuum tubes being
replaced with solid state active devices. From what I could determine most
conversions were driven by the lack of availability of the BR535 vacuum
tube (triode) used in the integral AC VTVM.? (I will repeat what I stated pre-
viously, the BR535 was a hand selected triode. A popular triode of the period
(I forget the industry part number for the tube) was purchased by Boonton
and each tube was tested for use in the Q Meter. Peter told me that culling
was dictated by an abrupt change in input impedance of the tube at 1 MHz.
Apparently there was a relatively frequent production error in manufacturing
the tube that caused the perturbation and Boonton's solution was to cull tubes
which presented with the undesired characteristic.

Another piece of information from my notes on the box is the resistors
R203 and R204 in the leads to the "Multiply by" meter are hand picked
at the time of installation of the thermocouple head. Apparently the
output voltage slope of the thermcouples varied and to compensate
for the delta between units, the resistor values were adjusted. Values
generally were between 30 ohm and 65 ohm. Equal value resistors
were used in each lead. The capacitors were in place to attenuate
RF that might couple into the sensitive "Multiply by" meter. The typical
0.01 uF value was chosen for service.

Many of the older units have a General Electric voltage stablilizer
block mounted on the floor of the box. In the last 20 years each one
I encountered either had failed or was in the process of failing. The
devices are enclosed in a stamped metal shell and filled with a 'GOO'
that makes a mess when the unit overheats. The GE boxes were
there to address line voltage fluctuations. Given the stench they
made when going up in smoke, I pulled the stabilizers out and use an
external UPS to provide well regulated AC power.

Please let me know if you notice any of the above info is in error and
also of any additions you might make.

Regards

Chuck WD4HXG

Thank you. Your comments certainly help understand why the things burn out so easily.

How does one know if the thermocouple assembly is faulty? I ask this from the view of a person that has bought a supposedly working 160-A from eBay from a seller with a rather poor feedback. The attraction to the auction was the unit appears in good physical shape and that the shipping charges were less than $30 from the USA to the UK. I don't yet have the meter, but would like to know how to run some checks when it arrives. I do have a couple of Boonton Q standard inductors. One covers 50 kHz to 150 kHz and the other 150 kHz to 450 kHz.

Dave

Today, I’d probably run the scenario in an EM simulator and get the capacitance that way. But there probably is some theoretical formula for this, perhaps with some experimentally-derived tweaks baked in. Even if there is vacuum or an inert gas in the can, such capacitor standards should be amenable to homebrewing with good results. ? The geometry of this design is inherently accurate and with some investigation of “how they did it”, should be quite reproducible - perhaps with even better results thanks to better modeling tools today, and all the low cost CAM for lead forming and such. If someone asked me to make a center plate, I’d just order a SMT stencil with a suitable singular circular hole in it. These are cut way more accurately than what can be done in a low-brow home workshop.?

Cheers, Kuba

15 aug. 2022 kl. 6:39 fm skrev Dr. David Kirkby, Kirkby Microwave Ltd <drkirkby@...>:

?I see a General Radio 0.01 pF 0.03% capacitor on eBay today



(image attached, as eBay links soon disappear).

These use 3 terminals, not 4. In the case of the 1 fF, 10 fF, 100 fF and 1 pF values, there are two capacitor plates with a grounded plate between them. The size of the hole in the plate determines the capacitance.

I wonder how one goes about determine the size of the hole? I'm interested if I could make something like this and put it on my Agilent 4284A and 4285A LCR meters. I have no idea what I would trust the mot - the LCR meter or my homemade capacitor. Both LCR meters are outside their calibration period, but both were calibrated within the last 5 years by Keysight, and have been in my possession since they were calibrated.

Dave

15 aug. 2022 kl. 6:39 fm skrev Dr. David Kirkby, Kirkby Microwave Ltd <drkirkby@...>:

?I see a General Radio 0.01 pF 0.03% capacitor on eBay today



(image attached, as eBay links soon disappear).

These use 3 terminals, not 4. In the case of the 1 fF, 10 fF, 100 fF and 1 pF values, there are two capacitor plates with a grounded plate between them. The size of the hole in the plate determines the capacitance.

I wonder how one goes about determine the size of the hole? I'm interested if I could make something like this and put it on my Agilent 4284A and 4285A LCR meters. I have no idea what I would trust the mot - the LCR meter or my homemade capacitor. Both LCR meters are outside their calibration period, but both were calibrated within the last 5 years by Keysight, and have been in my possession since they were calibrated.

Dave

?

On Sun, Aug 14, 2022 at 08:31 AM, Chuck Moore wrote:

The question was asked previously why the thermcouple heads
in the Boonton Q Meters were so fragile and prone to burnout
so easily.

<snip>

If you look at:

That's Brooke Clarke, who is a member of this list.

<snip>

Back to the Q Meter.

The thermocouple is heated by a short length of what is reported
to be nichrome wire. The writer at prc68 reports the wire is 37
gauge or 0.0045" in diameter. The nichrome wire heater and the
thermocouple both are mounted on the bakelight disc inside the
sensor head. and the thermocouple bead is welded to the heater
wire.

In looking at a chart which showed various nichrome wire gauges
and the expected temperature of the wire when a specified current
flows through the wire, 37 gauge Nichrome A wire would reach 1600
degrees F for 1000 milliAmps flowing through the wire.

Looking at the chart found here:



you can see a fairly wide range of temperatures for currents varying
from 350 milliAmps (400 degrees) to 1290 milliAmps (2000 degrees F).
The reported melting point for Nichrome A wire is 2,552 degrees F. The
current to reach 2000 degrees is only 29% over the current reported to
be flowing in the precision resistor in the Q Meter.

Ah, so the sense wire gets very hot. I assume that means ambient temperature changes are no so significant, as it's so far above ambient.

I thought I read in the 260-A manual that the RF signal generator only run at 50% of the power that could destroy the thermocouple, implying this would not happen like it did in the 160-A
But maybe I got that wrong.

If you examine the
scale of Boonton 260's Multiply Meter which is monitoring the current
through the nichrome wire, the meter is marked with a red zone that
begins at about 5% of the meter scale above the meter scale's "Multiply
by 1" mark. It appears that the heater operates at a temperature that is
was approaching 63% of the wire's melting point.

Em, I like to design things with a bit more to spare than that!

Peter Olin, AI2V (reported to be a silent key) at one time provided repairs
and conversions of the 260 Q meter to include sensor head repairs. I also
remember that one conversion of the unit led to the vacuum tubes being
replaced with solid state active devices. From what I could determine most
conversions were driven by the lack of availability of the BR535 vacuum
tube (triode) used in the integral AC VTVM.? (I will repeat what I stated pre-
viously, the BR535 was a hand selected triode. A popular triode of the period
(I forget the industry part number for the tube) was purchased by Boonton
and each tube was tested for use in the Q Meter. Peter told me that culling
was dictated by an abrupt change in input impedance of the tube at 1 MHz.
Apparently there was a relatively frequent production error in manufacturing
the tube that caused the perturbation and Boonton's solution was to cull tubes
which presented with the undesired characteristic.

Another piece of information from my notes on the box is the resistors
R203 and R204 in the leads to the "Multiply by" meter are hand picked
at the time of installation of the thermocouple head. Apparently the
output voltage slope of the thermcouples varied and to compensate
for the delta between units, the resistor values were adjusted. Values
generally were between 30 ohm and 65 ohm. Equal value resistors
were used in each lead. The capacitors were in place to attenuate
RF that might couple into the sensitive "Multiply by" meter. The typical
0.01 uF value was chosen for service.

Many of the older units have a General Electric voltage stablilizer
block mounted on the floor of the box. In the last 20 years each one
I encountered either had failed or was in the process of failing. The
devices are enclosed in a stamped metal shell and filled with a 'GOO'
that makes a mess when the unit overheats. The GE boxes were
there to address line voltage fluctuations. Given the stench they
made when going up in smoke, I pulled the stabilizers out and use an
external UPS to provide well regulated AC power.

Please let me know if you notice any of the above info is in error and
also of any additions you might make.

Regards

Chuck WD4HXG

Thank you. Your comments certainly help understand why the things burn out so easily.

How does one know if the thermocouple assembly is faulty? I ask this from the view of a person that has bought a supposedly working 160-A from eBay from a seller with a rather poor feedback. The attraction to the auction was the unit appears in good physical shape and that the shipping charges were less than $30 from the USA to the UK. I don't yet have the meter, but would like to know how to run some checks when it arrives. I do have a couple of Boonton Q standard inductors. One covers 50 kHz to 150 kHz and the other 150 kHz to 450 kHz.

Dave