Limits in pre-expression

[jvh75021]

Greetings (again...),

I am maintaining code written by someone with much more LV / TS experience than I have so I am hesitant to assume things are not right. The limits for a verification step are based on an earlier, retained result. But I see that on the limits tab are both zero and the following limits have put into the Pre-Expression field under Properties>Expressions:

Step.Limits.Low = Locals.LowFreqVcov + Parameters.VCO_HiFreqLoLimitDelta, Step.Limits.High = Locals.LowFreqVcov + Parameters.VCO_HiFreqHiLimitDelta.

Is this preferable to putting them on the limits tab?

Thanks,

jvh 

[James_Grey]

I'm guessing that sequence was written before the Numeric Limit Step supported expressions in the limits. It isn't wrong, but using the limits tab is now preferable because it is easier to see what is going on.

Message Edited by James Grey on 04-23-2010 09:55 AM

[Teds]

TestStand 4.0 ( and later ) added support to add expressions in the limits for Numeric Limit and Multiple Numeric Limit tests.  So before that you had to use pre-expressions to set dynamic limits.  I have done this on a couple of tests that I wrote per TestStand 3.5.

I do not think there is any harm in putting the limit values in pre-expressions, although maybe per a readability standpoint it differs because it is not evident where the limits are coming from.  Most of the test I write I use the Property Loader to read in the limits, plus when the value is 0 in the limits tab and there is no entry in the INI file it is a bit confusing. 

You could use the Property Loader and set the 'expression' value for the limits but if they work as pre-expressions why bother changing it?

Good day,

Paul Holzrichter

[jvh75021]

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Teds wrote:

You could use the Property Loader and set the 'expression' value for the limits but if they work as pre-expressions why bother changing it?

Good day,

Paul Holzrichter

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 Changing it would make it more readable for the next poor soul who follows me and like me stumbles for a bit before checking the expressions. Actually this code was written in 4Q09 by one who is an old hand at LabVIEW but uses TestStand sparingly. Since we were using 4.2 and I being a neophyte I thought that there must have been a good reason for.

 

Thanks all.