Would anyone consider an 8-pin microcontroller and Maxim/Dallas "one-wire" DS18B20 temperature sensors (-55°C to +125°C)?
Use 1 pin on the microcontroller to drive N number of sensors daisy chained on a 3 wire bus (+5v, Ground, and the "one wire" data I/O line). Use another two pins for serial I/O to the 'host'.
Simply connect the sensors to three wires at the correct intervals, add some insulation between, then pull it through the PVC pipe or other conduit before capping the ends and installing in the silo.
You could also use the extra microcontroller pins to drive a relay controller IC and easily add programmable "set points" to control fans or other devices. Program the "set points" from your 'host' device, disconnect the 'host', and let the microcontroller do all the work for you.
Please let me know if you need consulting help on this product?
Mike
**broken link removed**
**broken link removed**