Hello. Thanks to everybody for the help with this power meter. I've built up a system, using a diode bridge before the burden resistor, as suggested by Harold H. The output voltage goes to AN3 on a PIC18F242. The system is running, however the voltage read at AN3 is strange. The current sense transformer spec says that it will track current at 100 mV AC per 1 AMP AC. I do not see this occuring. For example, I have these measurements: (I used a handheld clamp meter to read these AMPs, the voltage is read using my system) 2.2 AMP = .13 V, 4.7 AMP = .26 V, 12 AMP = .57 V. So I measure anywhere from 100 mV AC per 1.69 AMP to 100 mV per 2.1 AMP. This also does not seem to be a linear mapping. I have double-checked my RMS firmware with some test data, and the algorithm implementation seems correct. Reading the output voltage with a volt meter produces different values, these values also do not correlate with 100 mV AC per 1 AMP AC. Does anyone have any ideas what I have done wrong? Thank you, Lou >Hello. >I'm building a power meter to measure how much AC current some electronic equipment is drawing (from 0 to 17 Amps). >I'm using a Triad Magnetics CSE187 current sense transformer. >This current sense transformer rates primary 0-240V 0-30 AMPs and secondary outputs 0-3.5V proportional to the current. >I have a 56 ohm resistor between the 2 transformer secondary pins, with one secondary pin (pin 5) to ground, and the other secondary pin (pin 8) routed to the analog input of a PIC18F242. >I'm using the PIC to perform the RMS current (IRMS) algorithm. >Here are my 3 questions: >Is there any circuit needed between the output of the transformer and the PIC analog input? >It seems to me that nothing additional is needed because the transformer secondary is 0-3.5V and the PIC analog is 0-5V. >Is this method accurate? >Is any calibration needed or possible? >Thank you, >Lou __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist