How can I use low pass fillter function to correctly filter data array from DAQ?

[nattapol_stp@chula.com]

I'm using DAQ to recieve thermocouple voltage attacted to AMUX-64T. I found powerline voltage, 50 Hz, is added to the thermocouple voltage. I'd like to eliminate it by using low pass filter function of LabVIEW. I try to connect low pass filter to "AI Read AI" directly, but I can't. How can I use low pass fillter function to correctly filter the data from DAQ? What type of filter should I use? Should I multiply the data before filtering? I need to see any example involed, if you can. I've attached "My VI.vi" file already. I would like to know where I should add LP filter. If you want any more detail, you can mail to me.

[Russell]

Hi,

Most people never use the low pass filter VI's for thermocouple measurements. Since you're only interested in a DC measurement, most people just oversample and average, just the way it looks like you already have your application. So I would go ahead and stick with the averaging method you are already using.

Try increasing the number of samples that you average and see if that makes a difference.

Russell
Applications Engineer
National Instruments
http://www.ni.com/support