Thermocouple Reference Junctions
Thermocouples are frequently used temperature sensors in industry. Temperature measurement with a thermocouple utilizes the Seebeck effect.
Thomas Johann Seebeck accidentally discovered that an electrical voltage is generated between two ends of a metal rod if there is a temperature difference (temperature gradient) in the rod. After connecting both ends, an electric current flowed, the magnetic field of which he detected with a compass needle. In 1821, Thomas Johann Seebeck succeeded in utilizing this effect in a first thermocouple.
In the Seebeck effect, an electrical voltage is generated between two points of an electrical conductor that have different temperatures. To measure the electrical voltage of a thermocouple, the thermocouple cable is connected to a universal measuring device. The connection material in measuring devices usually consists of copper. This is therefore a different material than that of the thermocouple. When connecting the thermocouple to the measuring device, two new thermocouples are created!
The use of a reference junction avoids errors in the measurement results.
Usually, the temperature of the transition point from thermocouple wire to extension wire is measured and electrically compensated as a reference junction. Knowledge of the reference junction temperature is a factor in the accuracy of the thermocouple temperature measurement.
With thermocouples, you always measure a comparison between a “hot” and a “cold” measuring point. If the “cold” measuring point is always kept at a known, stable temperature (e.g., 0 °C), this directly affects the precision of the temperature measurement. A calibrated Pt100 temperature sensor monitors the temperature of the reference junction.
This reference junction is also called cold junction compensation, CJC, thermocouple reference junction, reference junction compensation, or ice point thermostat.
Pre-assembled Reference Junctions
(Recommended for Type T thermocouples only)
Find the Right Thermocouple Reference Junction for Your Needs
The TRU 938 ice point thermostat provides a stable and accurate 0 °C (or elevated) reference temperature. It is a self-contained unit featuring Peltier technology, enabling maintenance-free operation.
Advantages of the ice point thermostat:
suitable for laboratory use
high capacity
suitable for high ambient temperatures
(up to 65 °C)
robust design
The TRU 937 ice point thermostat provides a stable and accurate 0 °C or an elevated reference temperature between 45 °C and 70 °C.
Advantages of the pre-equipped ice point thermostat:
for up to 100 reference junctions
compact design
adjustable desired reference temperature
selectable number and type of thermocouples for assembly
Connection via Klippon terminals or according to customer requirements (e.g., mini-connectors)
for use in high ambient temperatures
The TRUrac is a thermocouple reference system for 0 °C or elevated temperatures, mounted in a 19″ housing. It was developed for situations where the ambient temperature can be up to 65 °C.
Advantages of the ice point thermostat for control cabinets:
Mounted rack: 19″ chassis with built-in TRU 937 ice point thermostat
for installation in control cabinets
high capacity up to 200 double reference junctions
connection via Klippon screw terminals or according to customer requirements
standardized chassis fits into commercially available control cabinets
proven in power plants
The Hotbox is housed in a robust, waterproof IP66-rated enclosure and features a base plate.
Advantages of the reference junction:
predefined reference temperature between 45 °C and 70 °C
for use at very high ambient temperatures (max. 50 °C) and harsh environments
stability 0.05 °C
splash-proof housing
high capacity – up to 200 reference junctions
proven in power plants
Advantages of the reference junction:
Effective temperature 0 °C
for use at ambient temperatures between -20 °C to 70 °C
stability 0.05 °C
splash-proof housing (protection class IP66)
up to 100 reference junctions
proven in power plants
