[Test-Equipment] Q meter?

[Richard Knoppow]

----- Original Message ----- 
From: "Ray, W4BYG" <w4byg at att.net>
To: "'Richard Knoppow'" <1oldlens1 at ix.netcom.com>; 
"'Discussion of Electronic Test Equipment'" 
<test-equipment at mailman.qth.net>
Sent: Thursday, June 19, 2014 6:22 AM
Subject: RE: [Test-Equipment] Q meter?


>I have a 160-A that I picked up a couple of years ago, that 
>I've never tried
> to use.
>
> How does one test the thermocouple to insure it is OK?
>
> If OK, what precautions should one take in order to be 
> sure he does not ruin
> the thermocouple?
>
> Ray, W4BYG
>
> Kindness is the inability to remain at ease in the 
> presence of another
> person who is ill at ease, the inability to remain 
> comfortable in the
> presence of another who is uncomfortable, the inability to 
> have peace of
> mind when one's neighbor is troubled...     Samuel 
> Holdenson
>
>
     There is a 160 manual at BAMA. I think maybe also on 
one of the Hewlett-Packard sites. The main precaution is to 
set the coarse level at zero to begin all measurements and 
before changing bands on the oscillator.  If the 
thermocouple is burned out there will be no reading. The 
meter will also not read without an inductor on the test 
terminals. If you don't have made up coils just wind a coil. 
Several turns of nearly any wire on a toilet paper roll will 
do.  To measure small capacitors you do not need a known 
value of inductance, just anything that will give you a 
resonance.  See both the 160 and 260 books.  The Q-meter 
measures resonant rise in voltage across the tuned circuit. 
You can check Q by measuring the bandwidth between the half 
voltage poiints. By definition Q equals resonant frequency 
divided by bandwidth. This should agree fairly closely with 
the Q indication of the meter.  The Q meter has three parts: 
A calibrated oscillator with adjustable output level; a 
calibrated capacitor; an RF voltmeter using a thermocouple 
to measure the current through the tuned test circuit. It 
will measure inductance, capacitance and Q or quality factor 
of inductors. It will also measure Q or dissipation factor 
of capacitors but generally caps have a Q high enough to be 
masked by the coil losses.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com