Hi John,
On 8/23/22 3:13 AM, John Kolb wrote:
"Approximations can be made by resonating a coil on the Q meter, and
then noting the reduction in Q obtained when the capacitor is added."
If the Caps are equal, Qc = Q1*Q2/2*(Q1-Q2)
I believe measurement should be performed at same frequency. Attached is
a SimSmith model example. Using Voltage Ratio method as shown in
Suppose want to measure Q of a 120pF capacitor at nominal 4MHz.
Set up Q meter such that Q meter capacitor is 240pF, resonate a coil
near 4MHz. In the SimSmith example, C1=240pF L1 is an inductor selected
for nominal 4MHz resonance, 5.5uH and Q meter measured Q=99.987 at
4.3806MHz, as shown in Blue trace.
Add 120pF capacitor to Q meter and re-resonate to 4.3806MHz. In SimSmith
added capacitor is C2, 120pF with Q=1k. Q meter capacitor is now 120pF,
C3. Violet trace indicates Q=95.231
Calculated 120pF Qc = (99.987 x 95.231) / (2 * (99.987 - 95.231)) = 1001
John KN5L
