sum, integral

[Philipp Keller]

Hello
I'm trying to integrate an offline signal. It changes about every minute.
The
signal is the flow of a liquid, and I would like to get the Volume which
went
already through.
Can anybody help me?
Philipp

[toddho]

I have the same question.  Although my flow cycles between off and a value several times a day.  I have read that Integral PtbyPt will not work correctly on such a data set.  Any ideas?

TX

Todd

[Cory_K]

Why couldnt you just use a little simple math. They already calculated the flow, that would have been the hard part.

To find volume, you just multiply (average) flow by time, or sum all of the flows.

Message Edited by Cory K on 02-12-2009 11:36 AM

[toddho]

Hey thanks for reply.  I appericate your time.  The major downfall is that if the program is not running I loose that information to total.  So I am going to try and read from the DSC modue and totalize the logged points.  It just seems like this should have (propably has) been done already.

Thanks

Todd

[BruceAmmons]

I would be very careful.  If there is a slight error in your flow rate, your total flow number will be way, way off.  Make sure your flow rate is calibrated very well over the entire range that you are using.  Don't just go with the numbers that come with the flow meter.

For example, if your flow was zero and your flow meter reads 0.01, after 100 readings you might think that 1 unit of liquid had accumulated!!  This all adds up, especially when you sum over a long period of time.

Also, don't forget to multiply each sample by the amount of time it covers.  For example, if your flow rate is 1 unit/second and your next reading is a minute later, multiply 1 unit/second * 60 seconds = 60 units.  This is also a source for errors if the flow rate varies large amounts in short time periods.  It is best to measure very short time periods when summing to get volume.

Bruce

[toddho]

Very good point that I had not thought of...thanks!