trigger and gate problem

[tonytonytony]

hello,
I am working on a simple temperature monitor, I am trying to use the statistics Vi to give me the max and min values, but it only gives me them for the last sample acquired, yet what i need is the overall max and min from the entire sample, ive tried using trigger and gate function from the examples but this only gives me the maximums for a set period of samples [how can i change this on the front pannel?]

Thankyou

Tony

[tbd]

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tonytonytony wrote:
hello,
I am working on a simple temperature monitor, I am trying to use the statistics Vi to give me the max and min values, but it only gives me them for the last sample acquired, yet what i need is the overall max and min from the entire sample, ive tried using trigger and gate function from the examples but this only gives me the maximums for a set period of samples [how can i change this on the front pannel?]

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Hi Tony,  it sounds like the answer could be as simple as using a shift-register to buffer a "running" max-min and after obtaining the max-min for the current-sample, do a second max-min to update the "running" max-min.

It would be easier to advise if we had a subVI - or at least a screen-shot - to look at.

Cheers!

Message Edited by tbd on 02-23-2008 04:06 AM

[lav]

hi, thanks for the reply.
ive attached a copy of the Vi Im using, basically what i want to be able to do it either tell the trigger and gate when to stop sampling or to be able to specify the sampling time of the trigger and gate from the front pannel. im not sure if this would work though since if i wanted to know the max temperature over a few days it would be collecting a vast amount of data in the buffer [?] so i was thinking maybe i could sample every few seconds, transfer these max and min to an array then use the "max min array" vi to find the max from there?
sorry if thats abit messy!
thanks for your help
tony

[tbd]

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lav wrote:
hi, thanks for the reply.
ive attached a copy of the Vi Im using, basically what i want to be able to do it either tell the trigger and gate when to stop sampling or to be able to specify the sampling time of the trigger and gate from the front pannel. im not sure if this would work though since if i wanted to know the max temperature over a few days it would be collecting a vast amount of data in the buffer [?] so i was thinking maybe i could sample every few seconds, transfer these max and min to an array then use the "max min array" vi to find the max from there?
sorry if thats abit messy!
thanks for your help
tony

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Hi tony,

       The first example shows one way to keep a running max/min.  Honestly, I don't use the Express VIs and, for this app. I'd just use a "Wait Until Next Ms-multiple" to have a loop measure temperature periodically.  However, whether measuring temperature or voltage, when making such periodic measurements it's customary to collect multiple samples and average them.  I don't know what kind of temperature transducer you'll be using, but, FYI, thermocouples are especially noisy.  The reason it's important here is because, currently, you're max/min reflects every-single sample and noise-spikes might make your max/min temperature measurements several-degrees worse than reality.

Cheers!

Message Edited by tbd on 02-23-2008 10:07 PM

[lav]

thanks for the attachment vis, im running version 7 so they wont open - please could you re-post them as v7?
thanks alot
tony

[tbd]

Here you go...