LTSpice and power measurements

[Dave H]

To output the G2 dissipation in Spice the syntax for example a 5ms interval is

.MEAS TRANS POWER G2 INTEG (v(S)*Ix(U1:Screen))/0.005

Thanks, that worked. I had to change the interval to be the same as the plot window (10mS). With 5mS it gave twice the value. The answer is the same as the previous plot (7.3W) but the coloured sim was ever so pretty

[Helmholtz]

EL34 screen dissipation sim.

[ATTACH=CONFIG]52215[/ATTACH]

Interesting that the power curve looks very similar to the current curve.

[Helmholtz]

Thanks, that worked. I had to change the interval to be the same as the plot window (10mS). With 5mS it gave twice the value. The answer is the same as the previous plot (7.3W) but the coloured sim was ever so pretty

[ATTACH=CONFIG]52223[/ATTACH]

With that it should be easy to demonstrate that doubling the load impedance increases screen dissipation while plate dissipation and max. output power decrease.

[nickb]

Thanks, that worked. I had to change the interval to be the same as the plot window (10mS). With 5mS it gave twice the value. The answer is the same as the previous plot (7.3W) but the coloured sim was ever so pretty

[ATTACH=CONFIG]52223[/ATTACH]

If you want some time interval other than the window you can use the TRIG and TARG modifiers to specify the internal. For example a 2mS interval would be

.MEAS TRANS POWERG2 INTEG (v(S)*Ix(U1:Screen))/2M TRIG TIME=1M TARG TIME=3M

[Dave H]

If you want some time interval other than the window you can use the TRIG and TARG modifiers to specify the internal. For example a 2mS interval would be

.MEAS TRANS POWERG2 INTEG (v(S)*Ix(U1:Screen))/2M TRIG TIME=1M TARG TIME=3M

Thanks, I added it to the schematic but had to change 'TRANS' to 'TRAN' (or omit it as below) or it thought it was the measurement name and failed because 'two measurements can't have the same name'.

Syntax:
MEAS PowerG2 INTEG (v(G2)*Ix(U1:Screen))/0.010
MEAS PwrG2 INTEG (v(G2)*Ix(U1:Screen))/5M TRIG TIME=5M TARG TIME=10M

Result:
powerg2: INTEG((v(g2)*ix(u1:screen))/0.010)=7.33422 FROM 0 TO 0.01
pwrg2: INTEG((v(g2)*ix(u1:screen))/5m)=7.33401 FROM 0.005 TO 0.01

I'm sure to be scratching my head over the syntax when I come back to it in a few weeks time.

[nickb]

Yes, thanks. TRANS was a typo. I'm famous for them. I've contacted Berkley and asked them to change the syntax to match my typos so I don't look so dumb. In the meantime we'll just have to live with TRAN. I'm sure they won't take long. I've suggested a few new commands that we'll all love to have like

.SCHEM AUTO This draws the schematic that I have in my head
.MODELFIX This fixes all the deficiencies in whatever library models you are using.
.HCF Halt and catch fire. A more entertaining alternative to waiting hours for complex sim to complete.

[bea]

Well, i needed to make a short break with this and hope I'll get back to it over the weekend.