Why does the convert strain gauge reading vi output always shows a positive strain. When I run my test and place a strain to the test piece I receive a negative going signal, I can see this if I wire the strain directly to my waveform. However the output from the convert strain gauge reading vi is always positive. I have checked the wiring and all is fine. The force I am applying is compressive and should show a negative result. What I have done is add a multiplier function to the output of the convert strain gauge reading vi and put a constant of -1 to multiply the output by. This results are now negative as I believe they should be. If I put an opposite force (tensile) the output is positive. Basically, I want to know why the convert strain gauge reading vi automatically outputs a positive output regardless of the type of force which is applied
In theory that VI should output values according to what's listed in it's help file (http://zone.ni.com/reference/en-XX/help/371361G-01/lvinstio/conv_strain_read/) under Quarter I. Whether it's positive or negative should be determined soley by the values being fed to that equation. I suppose it's possible that the convert function assumes that you know which type of force you'll be reading and therefore takes the absolute value of whatever reading you're getting, but that seems a little strange. It's also possible some of the values you're putting in imply a positive result when they should imply a negative. Try checking your values against the equation in the first picture and see if anything jumps out as a sign problem.
