Re: .MEAS Failure
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Hello All:
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.meas TooLow1 FIND V(XSW11:X1:Qc,XSW11:X1:Qe) WHEN V(XSW11:X1:Qc,XSW11:X1:Qe)=2 FALL=1
works and produces;
toolow1: v(xsw11:x1:qc,xsw11:x1:qe)=2 at 0.00804696
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Zooming in the plot window to the end of the universe, I see this point.
8.0469636ms 2.0000203V
The next point is:
8.0469636ms 1.9999355V
The time values must have greater precision than can be seen because a node can't have two different voltages at the same time.
I now see that since there is no value in the data that is exactly 2.0000000 it had to perform a poor mans less-than function.
The code saw that 1.9999355 was less-than 2 where the previous sample 2.0000203 was more than two.
So that's a fall.
There was no test to see if data was ever == 2 as the .MEAS statement would imply.
I now see that the Fall and Rise modifiers mimic less-than or greater-than behavior for the .MEAS FIND WHEN statement.
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All for now
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Sent:?Monday, February 24, 2025 at 12:17 PM
From:?"eewiz via groups.io" <eewiz@...> To:[email protected] Subject:?Re: [LTspice] .MEAS Failure ?
Hello All:
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Sorry for being late to the party but I had to grab some sleep time.
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So, it's equality only.
No matter how many times I read the .meas help I would not come to that conclusion.
To me;?WHEN <expr> means WHEN <any and all types of mathematical experssion>.
WHEN <expr of equality only> would be much more redily understandable.
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I noticed that there were no examples of anything like:
Print the time if and when a power exceeds 5W.
Print the time if and when a collector-emitter voltage goes less than 2V.
Print the time if and when a snubbed node ever exceeds 15.6V.
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Those are always the type of questions that I regularly need answers to.
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Thanks very much for the examples.
I will see if I can get the answers I need using only equality.
? All for now ?
Sent:?Monday, February 24, 2025 at 11:24 AM
From:?"Tony Casey via groups.io" <tony@...> To:[email protected] Subject:?Re: [LTspice] .MEAS Failure On 24/02/2025 15:57, Andy I via groups.io wrote:
But I distinctly recall Helmut Sennewald cautioning people not to test for equality.? Better to use >= or <=.? The implication was that it did not use linear interpolation in those situations.? I thought .MEAS was one of them.This would be the case, for example, in a B-source expression, which disallows the "=" operator anyhow, e.g.: ? B1 EQ0 0 V=if(V(test)=0,1,0) ..which triggers an error, but: ? B1 EQ0 0 V=if(V(test)==0,1,0) ..doesn't. However, in the example of my simple sine source circuit, the 2nd of those expressions only results in V(eq0)=1 once at time=0, because none of the following data points result in V(test)=0, even though it is clear the waveform is periodic and passes through zero twice every cycle. This example therefore doesn't use interpolation, it simply looks at each data point. -- Regards, Tony |
eewiz