XPost: sci.physics, alt.solar.thermal   
   From: vaughnsimon@gmail.invalid   
      
   "Morris Dovey"  wrote in message   
   news:j8iil4$g4g$4@speranza.aioe.org...   
   > * If anyone would like to play along, I could use some help with a   
   combination   
   > heater/temperature sensor using an up to 16-inch (406.4mm) nichrome wire   
   > threaded through ceramic cores (inside a 1/4x4-inch copper tube that's closed   
   > on one end) with one side connected to ground and the other to a SPST relay   
   so   
   > that when the relay is powered, the wire will be heated with AC power; and   
   > when the relay is unpowered, the resistance of the wire can be sensed to   
   > determine its temperature.   
      
   I would urge you to reconsider that approach.  If you use a standard   
   temperature   
   probe (perhaps right inside that pipe with the heater), you not only gain the   
   advantage of using some standard "pre engineered" temperature sensing circuit,   
   you also can dispense with that relay and easily control the heater with a   
   standard SSR (Solid State Relay)  The varying contact resistance of that relay   
   would always introduce some "noise" into your temperature readings..   
      
   Vaughn   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)