My end goal is to measure the current of a solenoid through a shunt resistor, gaining the output and using an AD536A to give RMS values. The control signal to the solenoid will be a variable PWM with dither. I am using the AD536 with a single ended 12V supply and I plan on gaining the input to the AD536 to 5V full scale. When I put in a sine wave straight to the 536, I get the correct rms value. I put an input cap in series with the function generator input and it does not matter if I put an offset or not on the sine wave, I still get the rms value corresponding to a sine wave without the offset(ampl * .707). This alone seems wrong because the DC offset should increase the rms value. When I put in a square pulse, with offset to make it positive, I get a lower value than expected, which is something I can correct with gain. But, when I increase the duty cycle, the rms output goes down, and rms voltage out goes up when I decrease the duty cycle. This is opposite of what it should do. Does anybody have any experience with this chip and using it single ended?? I used an AD536A with a +/-12V supply and it seems to work well. Any suggestions are much appreciated.
Thanks in advance,
adwina2
Thanks in advance,
adwina2