zeroing LVDT

[solerpwr07]

I have setup a calibrated LVDT using the DAQ assist. Simple enough feature in my code: signal comes straight from the DAQ assistant, is subject to calibration math functions, and then out put to a numeric indicator. I want to be able to zero the LVDT when a button on the front panel is pressed. So say the lvdtis reading at a displacement already, I want that value to be zero and and any further displacement will be relative to that point. what a simple way of accomplishing this, unfortunately Im still learning trial by error with labview.

[paramesium]

hmm....last time i did something like this

i put DAQ inside a subVI

then when u press "initialise"button , u will get the data...

so...you let your main reading to minus up your second reading(which u get when u press "initialise" button)

put it in sequence structure if it is in the same loop

if it is not...creat a local variable...

hope u can understand what i am trying to say

[Jolt]

QUOTE (solerpwr07 @ Apr 8 2009, 03:46 PM)

I have setup a calibrated LVDT using the DAQ assist. Simple enough feature in my code: signal comes straight from the DAQ assistant, is subject to calibration math functions, and then out put to a numeric indicator. I want to be able to zero the LVDT when a button on the front panel is pressed. So say the lvdtis reading at a displacement already, I want that value to be zero and and any further displacement will be relative to that point. what a simple way of accomplishing this, unfortunately I'm still learning trial by error with LabVIEW.

I assume you have some sort of "structure" your code is running in - this could be a simple While loop or better, an event driven state machine...

Click on the outer edge of this structure and create a shift register - shift registers are you friends!

Initialize the register on the left hand side with a constant, probably a "0" as a double precision float (usually orange). When you get a LVDT reading subtract the the register value from it.

Most of the time you will wire the left and right registers together - this will pass the current value "around" again.

Create a "zeroing" case or event that allows you to put the base LVDT reading into the right hand register - this will be the new offset and will be "passed around" until you change it again.

Remember to wire the register "through" every case in multiple case structures.