Etape Channel Sampling And Conversion

[hschir]

I am required to collect both the raw voltages and the conversion data from an eTape.

I have set up DAQFactory channel (eTape1_V) to collect the raw (quantized) voltage is at 1 second intervals from eTape

A second channel is then required for the eVap data (eVap1),

My question is does the eVap channel:

1. read the second channel (eTape1_V) at 1 second intervals averages 60 of these samples and then apply the voltage to mm evaporation conversion, alternatively,

2. read the second channel at 1 second intervals apply the evaporation conversion to each of the 60 samples and then averages those results, but

I think it’s more likely to follow point 2, or neither of these ?

[AzeoTech]

If you need to collect both raw and converted values, its usually best to create two channels like you did, but make the second channel have a timing of 0, and use the Event of the first channel to put the converted value into the second. So, if you are actually reading voltage into eTape1_V, you'd go into its Event and put something like:

eVap1.addValue(eTape1_V * 10)

which would make eVap1 hold 10 times the value of eTape1_V. If you wanted a running 60 second average, you'd do more like:

eVap1.addValue(mean(eTape1[0,59]) * 10)

however, you won't get as much of a mean at the beginning.

[hschir]

The voltages are being collected in the first channel: eVap1_V

The second channel is called: eVap1_avg

The settings for the second channel are: Device: LabJack

Device number: 1

I/O Type: DigIn (because I have plenty of unused dig channels)

Channel: 9

Timing: 0

Conversion: Nothing

I already have the conversion in 'Conversions' its tag is: eTape_1

In the Event for eVap1_V I have:

eVap1_avg.AddValue(mean{eVap1_V[0,59]}*eTape_1)

It's not working - can you tell me why ?

[hschir]

Forget about my previous post - I've sorted it out now!

[hschir]

I will ask this - why did you say "however, you won't get as much of a mean at the beginning." ?

[AzeoTech]

Because when you start DAQFactory, unless you are using Persist on your channels, your eVap1_V channel won't have 60 values to average.

BTW: {} is not the same as () and should not be used as a substitution. It may work now, but is unlikely to work in future releases.