R

#### rickman

- Jan 1, 1970

- 0

best. It looks like there are a lot of third parties who are helping by

chipping in their shots at tutorials and docs. But they are mostly

introductions and getting started guides covering only the most basic

stuff.

I am trying to do what should be some simple measurements on a tuned

circuit. I want to see how various additions to a circuit alter the

tuned frequency, bandwidth and Q. So it would be nice to get these

numbers automagically. I've figured out how to get the bandwidth and

the tuned frequency and even the Q. But it printed the frequency and Q

in dB. The tuned frequency is no problem as it is also displayed

linearly, but I can't find a way to display the calculated Q as a simple

number other than doing the reverse dB calculation so it displays the

proper number but with a dB label... obviously not my first choice.

I can't find any docs on how I might tell LTspice how to format a

measurement display. Does that exist somewhere? Here are the commands

I am using...

..MEAS AC tmp max mag(V(N002,N001)); find the peak response and call it "tmp"

..MEAS AC BW trig mag(V(N002,N001))=tmp/sqrt(2) rise=1

+ targ mag(V(N002,N001))=tmp/sqrt(2) fall=last

..MEAS AC centerfreq WHEN mag(V(N002,N001))=tmp

..MEAS AC Q PARAM pow(10,centerfreq/(BW*20))

Here is what this displays

tmp: MAX(mag(v(n002,n001)))=(40.5139dB,0°) FROM 59000 TO 61000

bw=565.564 FROM 59716.6 TO 60282.1

centerfreq: mag(v(n002,n001))=tmp AT 60000

q: pow(10,centerfreq/(bw*20))=(106.089dB,0°)

It would be a bit nicer if this last line just displayed...

q: centerfreq/bw=106.089