Thermocouple Transmitter - HTCT

The HTCT "Snap-On" temperature transmitter amplifies signals generated by thermocouples which can be used for process control equipment. Standard output current signals are in the range of 0...20 mA or 4...20 mA. Because thermocouples can only detect temperature differences, there still remains the problem of calibrating and calculating the absolute temperature. Built into the HTCT is a platinum probe (connected to the unit's terminal connector) which measures the cold junction reference temperature. This is algebraically added to the measured thermocouple's signal to determine the absolute temperature. There are three configured options available: external, internal or without cold junction compensation. External compensation is recommended when the thermocouple is connected to the transmitter with copper wire. The remote platinum sensor is now located in the junction box where the thermocouple wire connects to the copper wire. It measures there the "junction" temperature. Long copper cabling does not added error signals along the line. The slection of the cold junction mode is programmable with wire jumpers on the screw terminals. Internal cold junction compensation is the same as the external. A platinum probe measures the temperature of the screw terminal and compensates for an absolute value.



Technical data 


13-bit, digital, typical linearity 0.1 %


Max. +/- 100 mV, diode protection, input impedance 1GW


Max. bandwidth 0.2 Hz


+/- 1 0C or +/- 12 mV whichever is greater

Zero error

+/- 5 mV / 0C (chopper amplifier)

Gain error

Typical 50 ppM / 0C

Cold junction compensation

1. No compensation. Wire jumper "X" from 4 to 5.

2. Internal compensation with Pt-1000 platinum probe. -10...+50 0C (14...122 0F). Wire jumper "Y" from 3 to 6.

3. External compensation with Pt-1000 platinum probe. The measurement is made in the thermocouple junction box. Compensated junction box temperature range. Connect the external Pt-1000 platinum probe to 4 and 6.

Signal current output

0..20 mA / 4...20 mA, impedance > 1 MW @ 20 mA, other outputs on request

Supply voltage

115 V / 60 Hz or 230 V / 50 Hz, ca. 5 VA, others on request


35 mm rail mounted, EN50022-35


280 grams





12-pole screw terminal, description as below.

1 = Signal input +

7 = Signal output +

2 = Signal input -

8 = Signal output -

3 = Cold junction compensation A

9 = not used

4 = Cold junction compensation B

10 = not used

5 = Cold junction compensation C

11 = Power supply N

6 = Cold junction compensation D

12 = Power supply L