How to use a running time elapsed in a Formula and...

[Michel_OC]

Hello to everybody:

I'm developing an Application based on SignalExpress 2010 for an Engine Test Cell, and it is intended for to acquire several analog input signals (Voltage & Temp). Actually it is complete and working fine, but now I would like to include & to show in Dataview a value resulting from a Formula Step.

I've two problems for to solve:

1) One of the parameters required for the calculation is not a "Input Signal". It is a real time elapsed since acquisition started. I couldn't find any "Timer" or similar tools for to count the elapsed time.

2) The other parameter is a "Input Signal", but I need to keep in a "Variable" the initial value for this input in order to use it in the Formula Step.

In order to clarify this issue, here the real example:

- My "Input Signal" is Fuel Weight (scaled voltage signal)

I need to calculate: Fuel Consumption Rate = (FWt ini - Fwt x) /time

     where: FWt ini = Fuel Weight at start running application (Initial value)

                FWt x =  Real time Fuel Weight value acquired.

                time = Time Elapsed since application started

As info, here my hardware: - NI-9178 DAQ

                                        - NI-9205 (32Ch, +-10V)

                                        - NI-9213 (16 Ch.Thermocouples)

I appreciate any help or any idea.

Thanks,

Michel Ontiveros

[Jim_S]

Hello Michel,

After reading your forum post, it looks like you want to take the derivative of your signal and your need to set a variable with the Initial value for your calculations. After looking into derivative function in Signal Express, there isn't a function in this program to do this. I have found though this example that has LabVIEW VIs that can be used in Signal Express in order to implement this. Is the derivative the only thing you need to implement or is there some other functionality you need with storing the initial value and creating a timer?