Analog signal conditioning is an overwhelming thing to Google!
Here is the problem: I need to measure a remote resistance of 0 to 500 ohms with the AD input on a Pic 16F877A. what ever I do, it has a lot of jitter on the reading. A super cheap Harbor Freight Ohmmeter works fine.
Details: The Ohmmeter is using a 0.22 ma current for measurement. My circuit has tried to series the top of the pot with 4.3k down to 680 ohms. I have tried up to 0.22 UF capacitor in parallel with the port to no avail. The ohmmeter works all the way to the circuit board so I cannot see how I could have a wiring error. My development board is powered by the USB port and the program works with the Board's 5K pot across VCC.
For the curious: The resistance I am trying to read with the PIC is at the end of about 80 feet of wire in my Ham Radio rotator. I took a lightning strike several years ago and have since dedicated a meter and toggle switch for a control box. I am just now looking for a better solution...
I am not looking forward to exploring Ohm meters!
John Ferrell W8CCW
"All that is necessary for the triumph of evil is for good men to do nothing." -- Edmund Burke
http://DixieNC.US--
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
