pressure

[ramair]

Users,

I am new to Labview and just started using the National Instruments hardware and software to update our test cells. One of the variables I am trying to measure is pressure for fluids flowing thru an "line". How do I go about measuring pressure. I am currently using a SCXI-1102B module with 1303 terminal block. Is that hardware going to be sufficient to record pressure? I do understand I will need an external voltage source for excitation of pressure transducers. How shall I go about doing this?

Thanks for the input.....

[Jordan F]

Hi!

The 1102B Module is an analog input module that accepts a voltage range from +/-10V.  Also, the 1102B module does give you access to a 5V pin but it is not necessarily used for external excitation.  However, this could work depending on the specifications on your pressure sensor.  Do you have pressure transducers that you are planning on using?  If so, could you post a link for me to check out the specifications on it?

The SCXI 1520 Module is specifically designed for measuring pressure, force, load and torque.  It has a 0-10 V programmable voltage excitation per channel.  If you were starting from scratch I would recommend using this module. 

The tutorial below explains the concepts and techniques of measuring pressure with pressure sensors and what NI hardware is recommended.

Measuring Pressure with Pressure Sensors

Cheers!

[ramair]

Thanks for your reply. I have a 1102 module with a 1300 terminal block and a 1102B module with a 1303 terminal block. We have already purchased these modules and terminal blocks, so I would rather stick with these instead of buying SCXI 1520 module.

As I was reading through the 1303 terminal block installation guide, it seems that 1303 will be more suitable for thermocouple measurements. Am I correct in assuming that? I was planning on using the 1303 terminal block in conjunction with SCXI-1102B. The thermocouple types that I will be using will be K-type. Another question on measuring temperature using thermocouples is whether the length of thermocouples change the reading? I plan on using 16 thermocouples of different lengths to measure temperature at 16 different locations.

I was planning on using the 1300 terminal block in conjunction with SCXI-1102 module for reading voltage output from pressure sensors. The pressure sensors that I will be using are Omega PX209-030A5V and PX105-200G5V. I will be using a DC power supply for excitation of the pressure sensors so I won't need the 1102 module as a source for excitation. The link to those omega transducers is http://www.omega.com/ppt/pptsc.asp?ref=PX209_PX219&Nav=preb03

Thanks for your help.

[Jordan F]

Yes, the 1303 terminal block with 1102B module is meant for thermocouple measurements so that will work great!  The only problems you may see when having long wires on your thermocouples is some noise.

As far as using the pressure sensors with the 1102 module/1303 terminal block, it should be fine. 

[ramair]

I did get the transducers and wired them up and they work just fine. On my earlier post, I believe I made an error when I said that I will be using the 1102 with the 1300 terminal block and 1102B with the 1303 terminal block. I meant to say the opposite. I will be using the 1102 with the 1303 terminal block as 1102 is a thermocouple amplifier and 1102B with the 1300 terminal block to wire all my transducers. Is that considered an acceptable pairing?

I had another question regarding measurement of RPM. We have a sensor here that measures frequency. I bought a frequency to voltage converter that will covert the frequency signal to voltage which I can then covert to RPM. Do you think that process is acceptable to measure RPM or is there a better way to measure RPM?

Thanks for your input.

[Jordan F]

Yes, that is considered an acceptable pairing.  Both the terminal blocks will work with the 1102 and 1102B modules. 

Regarding your other question, I am confused on how you are exactly doing the RPM measurement.  If you use a counter you could measure the frequency and then convert that to RPM using math.  Here is a helpful link on measuring frequency.

Frequency Measurements: How-To Guide

[ramair]

Hi Jordan,

Is there a way to "personalize" or format the way data is displayed when using Write to Measurement File express VI? I would like to change the formatting of data and time and maybe make the column widths to where the data dosent overflow into the nearby cells.

Is that the only way to write data to an excel spreadsheet or can I use other express VI or some other output method to create data file that I can format as I please ?

Appreciate your help,

Thanks.

[Jordan F]

Hi,

You could either use ActiveX controls or Report Generation Toolkit to change the formatting of you excel file.  The ActiveX interface can be pretty complex though so if you are not familiar with it I would recommend to look into the Report Generation Toolkit.  I attached a couple articles on how to use ActiveX commands as well as a link to the Report Generation Toolkit to check out. 

Programmatically Setting the Column Width in Excel to AutoFit Using LabVIEW

Using National Instruments Software to Control Microsoft Excel with ActiveX