¿ªÔÆÌåÓý

ctrl + shift + ? for shortcuts
© 2025 Groups.io
  1. HBTE
  2. Topics

Q-metering

 

I would like some way of measuring the Q of inductors up to at least 30 MHz - 150 MHz would be nice.?

I have an HP 4284A Pr¨¦cision LCR meter (20 Hz to 1 MHz 0.05% basic accuracy) and a 4285A (75 kHz to 30 MHz, 0.1% basic accuracy). However, although these figures of 0.05% m n ? ? My mmand 0.1% might sound impressive, these are only achieved at a very limited set of circumstances. There¡¯s an example in the 4285A manual of a measurement the Q on an inductor. I forgot the exact numbers, but they are similar to these

* 220 nH
* 25 MHz
* indicated Q = 30

Measurement uncertainty +107/-13.?

So all it really says is that the Q id somewhere between 17! and 137.?

So I was looking for ideas on building a Q meter..?

Dave, G8WRB?


--
Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...

Telephone 01621-680100./ +44 1621 680100

Registered in England & Wales, company number 08914892.
Registered office:
Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom
 

One approach:?
There is a presumption that the effective (loaded by scope and coupled pulse generator) tank capacitor Q is good enough so the inductor Q dominates what you see in the ring-down, something to be tested in your experimental setup.

Another coupling means:? A low capacitance, high speed switching diode can be used to isolate the pulse generator after the pulse.? Generators that allow offsetting the baseline allow the diode then be driven deep into reverse bias if it matters to minimize diode capacitance.?

Wally
 

On Tue, Jul 26, 2022 at 07:56 PM, I_am Wally wrote:
One approach:?
There is a presumption that the effective (loaded by scope and coupled pulse generator) tank capacitor Q is good enough so the inductor Q dominates what you see in the ring-down, something to be tested in your experimental setup.

Another coupling means:? A low capacitance, high speed switching diode can be used to isolate the pulse generator after the pulse.? Generators that allow offsetting the baseline allow the diode then be driven deep into reverse bias if it matters to minimize diode capacitance.?

Wally
Thank you for that. It was not a technique I was aware of.

1 - 3 of 3