Hi, I'm a newbie to this board and hope someone here can help me out. I've trying to troubleshoot an erratic reading on a cylinder head temp gauge for automotive use. It uses a K type thermocouple (grounded), a 'black box' amplifier and an analog gauge. The operating range is 0F-600F, and the amp ranges 0-5 [vdc] output. Here's the problem, with everything wired, the amp wired directly to the car battery and the TC screwed to the head I get a fairly accurate reading,,, provided the ignition is OFF. As in the TC setup is hardwired to the battery. As soon as I turn the key to the run position (engine not running but car powered up) the gauge shows ready about 30% high. Start the engine and it just bounces all over the place.
There's a few more scenarios I haven't had time to try yet like floating TC ground though it's not possible in this situation, but you get the idea. Just trying to ID the problem and go from there.
I've done a little research on this topic, but I'm still a rookie so if I have something really wrong let me know. My first thought was potential difference at grounding points (ground loop?) so I tied the grounds together and still no luck. Then thought Alternator noise, tried a genereic Radioshack filter kit for Auto use, still no change. The only way I can seem to get this to work is with a separate power source, but that's not really practical unless someone knows of an easy way to achieve this. Maybe a line conditioner on the power lead to the amp? Anyone have any ideas?
Thanks much, --Ryan
There's a few more scenarios I haven't had time to try yet like floating TC ground though it's not possible in this situation, but you get the idea. Just trying to ID the problem and go from there.
I've done a little research on this topic, but I'm still a rookie so if I have something really wrong let me know. My first thought was potential difference at grounding points (ground loop?) so I tied the grounds together and still no luck. Then thought Alternator noise, tried a genereic Radioshack filter kit for Auto use, still no change. The only way I can seem to get this to work is with a separate power source, but that's not really practical unless someone knows of an easy way to achieve this. Maybe a line conditioner on the power lead to the amp? Anyone have any ideas?
Thanks much, --Ryan