signal express data logging and signal procesing

[uÖzkan]

I have two questions that want to ask about Siganal Exptress capabilitiy.

1. can we log the data with this program or how long data size can we log.İf it is yes. So what is difference between VI logger and Signal Express

2. Can we calculate energy that applied the any system over voltage and current. It means that formula tool is enough for calculating integral or somethink like that.

[John_P1]

Hello teknosat,

SignalExpress can indeed log data.  There is not really a specific maximum data size that you can log (although programs such as Excel have limits to how much data they can display).  SignalExpress is a more recent product designed to replace VI Logger (although it is a larger package).  If you already have VI Logger, you may want to see if it accomplishes what you need.  If you are purchasing new software, SignalExpress is what we recommend since it provides more features and is being actively developed.

You can use SignalExpress to compute the power spectrum of your signal.  You can also sum the values of an array of data since we are talking about digitized (i.e. discrete) signals.  You can always download a free trial of SignalExpress to see if it will work for what you need to do.  Be sure to let us know if you have any questions about it, and good luck with your application!

-John 

[uÖzkan]

Exactly i want to measure energy that consumed by Cooling Machine using Signal Express.

In addition using of power spectrum how is a that ? If anybody can explain of that i will be glad more

[Chris_W.]

Hello,

To use get a power spectrum signal in signal express you have to add a step after your DAQmx Acquire Analog Input step that is called Power Spectrum. I have attached 2 images. One called Add Step.jpg, that shows you where to get that power spectrum step and one that shows a power spectrum measurement when acquiring a slow sine wave on my hardware.

Chris

[uÖzkan]

 Maybe the issue was appeared wrong because of i had tried to measure energy that consumed by cooling machine.

Current issue is how can i measure this energy using signal express.

For example should i measure main voltage and current of machine and then what?

[Chris_W.]

If you know the load of your "cooling machine" then really all you need to do is to measure the voltage across the load and then send that data into one of the signal pricessing steps called "Formula." I have attached another image that shows how you can configure that step. If you simply take the voltage you read across the load, then you can use the equation Power = (V^2)/R. In the case that the attached image is for, I'm assuming the load is 100Ohms.

Chris

[uÖzkan]

Thanks a lot for yours helping but there is another issue about measurement power that to calculate power factor cos(fi).

ı have attached a file thas is explaining how we can calsulate the cos (fi). In this case the issue is whether Signal Express can calculate this mathematical equation or not.

II know that Labview Base can calculate easely this equation but i need to make  the data loggnig. So that i try to use Signal Express

[John_P1]

Hi teknosat,

The Formula Step should be what you need, provided you have the full version of SignalExpress. 

You can log data in LabVIEW as well if this is what you need to do (e.g. you can use the Write to Spreadsheet File VI).

-John

[uÖzkan]

Now i realize that i won't be able calculate cos (fi) using Signal Express. So that i have to use Labview.

But at the same time i want to measure temprature through 64 channel with signal express. In that case how i will see all channels on one screen ?

[Chris_W.]

I don't understand why you can't do Cos(phi)? "Cos(x)" is a valid statement in the formula step. If you go into the signal express help and search for the page named "Formula" in the Index tab you'll find a list of all valid expressions. You will have to define what phi is, or you can calculate what phi is using acos(x).

As far as reading in 64 channels of thermocouples, you will simply have to do a DAQmx Acquire step in SignalExpress and when you are selecting your channels you can select multiples by doing either Ctrl+click or Shift+shift. This will output all channels you select. You can also configure different properties for each of the channels in the DAQmx Acquire window. 

Chris