Instrumentation

A temperature controller holds something at the temperature you set, switching a heater or a cooler through its own relay. Waveinverter stocks plain digital thermostats for fridges, freezers, glasshouses and fermenting, PID controllers for kilns, furnaces and heat treating where overshoot matters, a dual relay model that runs a heater and a cooler off one setpoint, a defrost model for chillers that need to clear ice, a combined humidity and temperature unit, and a differential controller for solar hot water and pools. The probe decides the range: an NTC sensor covers everyday refrigeration and glasshouse temperatures, a K type thermocouple reaches 1250°C and an S type 1300°C, and an RTD PT100 suits liquids where you want a tight reading. Nearly everything here is mains powered, with one 12V DC model for off-grid, boats, caravans and trucks. Size the relay to the peak amps your load will pull rather than its running figure, and switch anything larger through a contactor or a solid state relay.

Do I need a PID controller, or will a plain thermostat do? A thermostat will let the temperature wander either side of your setpoint, which suits a fridge or a glasshouse, so pay for PID only where overshoot actually costs you something, like a kiln or heat treating.