Thermistor used as temperature sensor

Fred, you're somewhat outdated, there are standard products which offer 0.5%

Rene

For the largest, most linear signal right around one temperature, use a series resistor equal to the resistance of the thermistor at that temperature, only (about 15k for the thermistor you described, earlier. Linearity doesn't matter much when you will hold one temperature.

OK, I give in. All I want to do is measure the temperature of an airflow and maintain it at 70C +/- 1C. On playing further with my Excel spreadsheet, I've found that by using a 100k (25C) thermistor, a 14.3k ballast resistor at the GND end of the thermistor and measuring across the fixed resistor, the transfer characteristic is almost linear between 50C and 90C. That's good enough for what I need.

For a heater I intend to bolt 4 off aluminium clad 150W/500R resistors to a Marston FC-C1 fan assisted heatsink. The resistors will be run from 240VAC controlled by an opto-isolated solid state switch with zero crossing detection and should dissipate ~115W each.

Thanks to all for their interest.

statement.

that may not be a

Exactly. They are a waste of space IMHO.

Graham