Computing quantities with .meas statement

QSPICE
1

Hi,

I am testing a MOSFET turn on and turn off energy. For that I integrate the power dissipation and do the difference between on and off with the .meas statement:

.meas Eon_S2_B find V(energy_S2) at 29.98µ 
.meas Eon_S2_A find V(energy_S2) at 30.06µ
.meas Eon_S2 Eon_S2_A - Eon_S2_B

That works nicely, but I wouldn’t say the readability is very high:

.meas eon_s2_b find v(energy_s2) at 29.98µ:
     3.80971e-06  2.998e-05
.meas eon_s2_a find v(energy_s2) at 30.06µ:
     4.06061e-06  3.006e-05
.meas eon_s2 eon_s2_a - eon_s2_b:
     2.50901e-07  3.598e-05

Especially since I have this code repeated 4 times in a single simulation, so I was wondering whether it is possible to hide the .meas statements which are not the final answer, i.e.:

.meas Eon_S2_B find V(energy_S2) at 29.98µ 
.meas Eon_S2_A find V(energy_S2) at 30.06µ

Alternative ways of doing this calculation are welcome (hopefully I can avoid the C block).

Thanks and regards

2

I created a power, charge, and energy probe symbol that you can download from my Symbol Library in the fixture folder. Here is an example of how it may be achieved.

example.MOSFET-ON-OFF-PCEProbe.qsch (8.5 KB)

image
image1508×711 76.3 KB

3 Likes
3

Hi KSKelvin,

That’s truly remarkable, even the symbol looks great.

Thanks and regards

4

Let me know if it works in your case. Basically, it captures the differential voltage (+ve at the current probe node; -ve at the user-connected node). Therefore, with voltage, current, and time, it computes power, charge, and energy over time. An external reset allows resetting the integrator in the math for switching application measurement. However, since I built this symbol, I seldom use it. If there are any mistakes I made, please let me know.

1 Like