On Fri, Dec 4, 2009 at 10:08 PM, Research Faraday wrote: > I have another issue now. When I connected the 0-20V of a DC RPS, my output > was stable and the values didn't change frequently. Now, I connected the > output of the sensor to the display. When there is no output voltage, the > value of the display keeps changing frequently. i.e 0.01, -0.01, 0.3 etc and > this seems to be highly fluctuating. I am told that the quality of the > components used in the meter is low. > > I checked the same output from the sensor using a multimeter. The value > seems to be relatively stable. When the sensor is idle, the output voltage > is 0.16V and when the output is maximum, the output is 5.01 V. > > I read the ICL7107 datasheet and I came to know that the ADC reacts to the > reverse current from the LEDs and grounding the digital and the analog > signals is necessary. I am going to try grounding the display's ground and > my sensors ground to the body of the enclosure. > The grounding is probably a good idea. It would be nice to look at the signal with an oscilloscope to see what kind of noise is there. I recall you have a voltage divider made of 100k ohm and 9.9M ohm resistors. Try adding a 10 uF capacitor in parallel with the 100k ohm resistor. This will give a low pass filter with a one-second time constant. Regards, Mark markrages@gmail -- Mark Rages, Engineer Midwest Telecine LLC markrages@midwesttelecine.com -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist