Thermostat and Temperature Controller Selection Guide
A temperature controller compares the temperature read from a sensor with the set value and drives a heater or cooler; a selection and sensor guide.
What a temperature controller is and where it is used
A temperature controller is a panel-mount device that compares the temperature read from a sensor such as a PT100 or thermocouple with the set value, and drives a heater, a cooler or an alarm through a relay, SSR or analog output. The same device is also called a thermostat, digital thermostat, PID controller or temperature control relay. It is used in oven, mold heating, machine and cold room panels.
A search for "thermostat" usually means a room or boiler thermostat. This category mainly lists industrial panel-mount controllers; Siemens room and fan coil thermostats are also included. For thermostats that heat or cool the inside of an enclosure, see the Panel Thermostats category.
Types of temperature controllers
- Analog Temperature Controllers: thermostats where the set value is entered in analog form; its subcategory is Analog Thermostats.
- Digital Temperature Controllers: devices with a display; On-Off Thermostats, PID Thermostats, Universal Controllers and Cold Room Control Modules belong to this group.
- Humidity and Temperature Controllers: devices that monitor relative humidity as well as temperature; for example the ON/OFF GEMO LT102HT and the Enda EHTC7425A with RS485 Modbus output.
What to look at when choosing a temperature controller
- Sensor and input type. The input type of the device must match the sensor to be used. On universal devices the input is selected by parameter; in the Enda EU4430 manual, PT100 and J, K, L, T, S and R thermocouple types can be selected. The scale range can be narrower than the sensor's own range: the same manual gives a scale of -30 ... 1300 °C for type K and -200 ... 600 °C for PT100.
- Control type. ON/OFF control switches on and off with a hysteresis around the set value and is used for simple jobs. PID control continuously calculates the output power and aims to keep the temperature close to the set value; it is preferred for loads such as ovens or molds. The auto-tune feature (Self Tune, Auto-Tune) lets the device calculate the PID parameters. According to the Enda manual, the device operates as ON-OFF when the proportional band is set to zero.
- Output type. Relay, SSR drive or 4-20 mA analog output is available. The current rating and switching life of a relay output are limited in the manufacturer's catalog. For loads that are switched frequently by short-period PID, an SSR drive output and Solid State Relays (SSR) are considered; the selection is made according to the load and the manufacturer's data.
- Alarm and sensor failure. The alarm relay, a second control output and the state the output takes when the sensor breaks vary by model; the Enda manual states that the output behavior can be selected in case of sensor failure.
- Size, supply and communication. The panel cut-out varies by model; for example it is 48 x 48 mm according to the Enda EU4430 manual and 72 x 72 mm according to the product name of the Tense DTA-72. The supply is distinguished in the order code: for the EU4430, the UV code means 90-250 V AC and the LV code means 10-30 V DC / 8-24 V AC. The RS485 Modbus RTU option is specified separately in the order.
Connection and commissioning are carried out by a qualified electrician according to the project and the manufacturer's data.
The difference between PT100 and thermocouple
A PT100 is a platinum resistance sensor; it has a value of 100 ohms at 0 °C and its resistance increases with temperature. A thermocouple, on the other hand, consists of the junction of two different conductors and produces a temperature-dependent voltage through the Seebeck effect. As a general rule, the resistance sensor gives more accurate and stable measurement at medium temperatures, while the thermocouple reaches higher temperatures and responds quickly. The device scale ranges reflect this: in the Enda EU4430 manual the scale for PT100 ends at 600 °C, while for a type K thermocouple it goes up to 1300 °C.
This difference is decisive when matching the sensor and the device: the input type of the device must match the sensor. When a thermocouple is routed away from the device, manufacturer manuals require a suitable compensation (extension) cable; for this, see the Thermocouple and PT100 Compensation Cables category. For the sensor itself, PT100 probes and thermocouples are in separate subcategories under the Temperature Probes category.
Brands in this category
- GEMO: ON/OFF and PID temperature controllers, an Auto-Tune PID model with timer relay, a temperature and humidity controller.
- Enda: digital PID thermostats, universal controllers and a humidity and temperature controller with RS485 Modbus output.
- Tense: temperature controllers such as the 72 x 72 mm PID model DTA-72, the AD-96 with analog setting and digital display, and the 28 x 70 mm DT-DF1.
- Siemens: electromechanical and electronic room thermostats, models with LCD display, battery-powered or RF wireless models, fan coil thermostats.
- GMT: PID controllers such as the GTC12A and GTC41S-TC.
Order notes
Products are sold per piece. Some products are listed as "made to order"; for these products the lead time is confirmed at the time of the order. You can search by model and stock code. Sensors and compensation cables are listed in separate categories.
Comparison and selection table
| Selection Criterion | Mechanical Cabinet Thermostat (NO / NC) | Digital On/Off Thermostat (NTC / PTC) | PID Temperature Controller (PT100 / Thermocouple) |
|---|---|---|---|
| Sensor Input | Built-in bimetal element (0–60 °C enclosure air temp) | NTC or PTC probe (-50 °C to +150 °C HVAC/refrigeration) | Universal input: PT100 RTD, Type J, K, T, S thermocouples |
| Control Algorithm | Simple mechanical snap switch (Blue NO = Fan, Red NC = Heater) | On/Off hysteresis control with compressor delay & defrost | Auto-tune PID control (holds exact setpoint without overshoot) |
| Output Stage | 250 V AC 10 A dry contact on 35 mm DIN rail | Electromechanical relay output (panel cutout 35×77 or 48×48) | SSR voltage pulse output (12–24 V DC), Relay or 4–20 mA |
| Typical Application | Control panel filter fans & anti-condensation heaters | Cold rooms, chillers, boilers, incubators & food cabinets | Extruders, injection molding, industrial ovens & heat sealers |
Frequently asked questions
What is a thermocouple?
A thermocouple is a temperature sensor formed by joining the ends of two different conductors. When the junction is heated, a very small temperature-dependent voltage arises through the Seebeck effect; the temperature controller converts this voltage into temperature. It comes in types such as J, K, T, S and R, and the input type of the device must be selected to match the sensor.
What is a PT100?
A PT100 is a resistance temperature sensor with a platinum element. The number in its name indicates that it shows 100 ohms of resistance at 0 °C; its resistance increases as the temperature rises. The temperature controller measures this resistance and converts it into temperature. Its characteristic is defined by EN 60751, and the device input must be selected as PT100.
What is the difference between PT100 and thermocouple?
A PT100 is a resistance that changes with temperature, while a thermocouple produces a temperature-dependent voltage. In general, a PT100 measures more accurately and stably at medium temperatures; a thermocouple reaches higher temperatures and responds quickly. The two cannot be connected in place of each other; the device input is set according to the sensor type used.
What is the difference between a thermostat and a PID temperature controller?
A simple thermostat works ON/OFF: it switches the output on when the temperature falls below the set value and off when it rises above it; because of the hysteresis in between, the temperature fluctuates around the set value. A PID device calculates the output power and aims to keep the temperature close to the set value; it is preferred for precise jobs such as oven and mold heating.
Should a relay output or an SSR output be chosen on a temperature controller?
A relay output directly switches the load or the contactor coil; its current rating and switching life are limited in the manufacturer's catalog. An SSR output drives an external solid state relay and is used for heater loads that require frequent switching, such as PID. The selection is made according to the load current and the manufacturer's data.