Programmable Thermocouple Converter

The Sensor Signal Conditioner type 4.0-LTCI-XX is a Programmable Thermocouple (TC) Interface Unit with Diagnostic and Alarm capability. The unit can be programmed to interface to standard Thermocouple types J, K, B, E, R, S, T, & N. Thermocouple Temperature ranges for Full Scale output signal are selectable to obtain maximum resolution of the analog output signals.

This unit performs the function of converting a TC signal into Single or Dual Isolated and Linerarized 4-20mA output signals. Complex software algorithms ensure very good stability and linearity levels of 0.1% of FS are achieved over the entire input range.
In-built Cold Junction Compensation (CJC) facility is provided. The user has the option to ENABLE/DISABLE the CJC function in the analog output of the module.

The unit incorporates an additional Diagnostic feature of “SENSOR FAULT (SF)” detection and ALARM output. The in-built unique sensor checking circuit performs a periodic Health Check operation to detect sensor fault. When a fault condition is detected it activates the “SF” indication (Red LED) on the front panel on the module. A logic output signal (24VDC) is also provided by the module which is used as an Alarm signal to warn an external control system about Sensor Fault condition.

Additionally a DIP switch is provided to allow the user to select the output signal value set by the module in case of a Sensor Fault condition. The following options are selectable,

  • UPSCALE on Sensor Fault i.e. O/P > 22mA.
  • DOWNSCALE on Sensor Fault i.e. O/P< 3.6mA.
  • HOLD LAST VALUE on Sensor Fault.
  • Do nothing. i.e. Output will follow Input (0mA on Sensor Fault.)

In a Dual output type unit, both the outputs can be individually set by the user to be set to any of the above values in case of SENSOR FAULT condition.

Output Wire Break (WB) indications are also provided on the unit. This will indicate 4-20mA Output Open Circuit condition or load resistance >1KOhm across output. Other LED indications provided on the unit are, Input UNDERRANGE (UR), OVERRANGE (OR), & SYSTEM HEALTH (SH).

The unit is offered with factory programmed TC type selection, CJC ENABLE/DISABLE & Temp. Range setting. The user can configure the DIP switch settings to set output response in Sensor Fault condition.

Ordering Information

Model Numbers
Single Channel (4-20mA) Output with Alarm O/P (4.0 – LTCI – A1) Dual Channel (4-20mA) Output with Alarm O/P (4.0 –LTCI – A2)
Single Channel (4-20mA) Output with Alarm O/P (4.0 – LTCI – 1) Dual Channel (4-20mA) Output with Alarm O/P (4.0 –LTCI – 2)


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  • Programmable Thermocouple (TC) Amplifier unit with Diagnostic & Alarm
  • Programmable TC type selection ( J, K, B, E, R, S, T, N)
  • Programmable temperature range selection for 4-20mA O/P.
  • Software linearization algorithm achieves accuracy better than +/- 0.2%.
  • In-built Cold-Junction compensation (CJC) with Enable/Disable option.
  • Sensor FAULT (SF) detection with Digital Alarm Signal O/P.
  • DIP-Switch setting of 4-20mA O/P signal value on SF condition. (Under Range / Over Range / Hold Last Process Value)
  • Output Wire Break (WB) indications.
  • Dual 4-20mA O/P with individual setting of O/P value on SF

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Thermocouple Input Signal Input Options: J Type(-210 to +1200°C)* Factory Set
K Type(270 to +1372°C)*
E Type(270 to +1000°C)*
B Type(0 to +1820°C)*
R Type(50 to +1768°C)*
S Type(50 to +1768°C)*
T Type(270 to +400°C)*
N Type(270 to +1300°C)*
(*: Max. Measurement Range)
Cold Junction
Provided In –built
Output Signal Output Options: 4-20mA.
No of Outputs Two (Max)
Load Resistance For Output Current 1KOhm Max.
Performance Accuracy ±0.2% of Span
Linearity TC Input (mV)v/sOutput:0.1%
Linearization TC non-linearity is compensated by the unit.
Temperature Drift <0.01% / °C
Response Time < 500mSec
Alarm Output Active on SENSOR FAULT condition.24VDC, 50mA (Max.)
Dip Switch Setting Allow the user to select the output signal value set by the module.
Calibration Span (Trimpot )


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Isolation 2KV – 3 Port.
Leakage Current <5mA.
Power Supply Voltage 24VDC(nominal)
Operating Range 18 to 36 VDC
Ripple < 100mVpp
Power Supply Current 200mA.Max
Enclosure ABS Plastic, 35 mm DIN Rail Mounted. IP40 Protection class. Single Output W – 45mm
H – 75mm
D – 115mm
Termination Screw type terminals suitable for 1.5mmsq. Wire
Operating temp. range 0 – 60°C
Storage temp. range 0 – 80°C
Relative Humidity 0 – 90%
RH Non-Condensing
Max. Altitude 3000 mts above MSL


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Programmable Thermocouple Converter

Pin Details
1 + I/P (TC Input)
2 – I/P (TC Input)
3 SHLD (TC Input)
4 + 24V DC (Supply)
5 GND(Supply)
6 Alarm O/P
7 – (O/P)Output2
8 +(O/P)Output2
9 – (O/P)Output1
10 +(O/P)Output1


In case of a sensor fault condition.(Refer Table 1.1)
LED Indications System Health : SH (Green/red)
Under range UR (Red)
Over range OR (Red)
Sensor Fault Both UR & OR (Red).
O/P 1 Open WB1 (Red)
O/P 2 Open WB2 (Red)


Switch No. Switch Position Function Description
1 2 OFF OFF CH1: UPSCALE on Sensor Fault i.e. O/P > 22mA
1 2 OFF ON CH1: DOWNSCALE on Sensor Fault i.e. O/P< 3.6mA
1 2 ON OFF CH1: HOLD LAST VALUE on Sensor Fault
1 2 ON ON CH1: Do nothing i.e. Output will follow Input (0mA on Sensor Fault.)
3 4 OFF OFF CH2: UPSCALE on Sensor Fault i.e. O/P > 22mA
3 4 OFF ON CH2: DOWNSCALE on Sensor Fault i.e. O/P< 3.6mA
3 4 ON OFF CH2: HOLD LAST VALUE on Sensor Fault
3 4 ON ON CH2: Do nothing i.e. Output will follow Input (0mA on Sensor Fault.)


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Additional information

Input Types

Thermocouple Sensor

Output Signal

Current 0-20/4-20mA (4 Wire), DC Voltage (+/-10V)


ABS Plastic

Product Type


Thermocouple Type

Programmable Thermocouple


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