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Two Wire Temperature Transmitters

Two Wire Temperature Transmitters

Product Specification :
Model wise descriptions :

Model Products Description
LTX - 3000 - H Two Wire Temperature Transmitter (Head Mounted) for Simplex
LTX - 3000 - H - 2 Two Wire Temperature Transmitter (Head Mounted) for Duplex
LTX - 3000 - WI Isolated Two Wire Temperature Transmitter
(In Weather proof enclosure field mounted)
LTX - 3000-D Two Wire Temperature Transmitter (DIN Rail Mounted)
LTX - 3000 - DI Isolated Two Wire Temperature Transmitter (DIN Rail Mounted)
LTX - 3000 - FLP Two Wire Temperature Transmitter in Flame Proof Head

Description :

Libratherm offers Miniature Head Mount Two wire Temperature Transmitter Model LTX-3000-H, which accepts (Pt-100) or thermocouple or variable resistance signal as the input and provides dc current output of (4-20) mA proportional to mV or resistance values. These transmitters are extensively used to minimize the effect of electrical noise and to eliminate the need of long runs of special compensating and three wire cables since ordinary pair of copper wires can easily be used to transmit the measured temperature without the drop or loss of signal. In addition, transmitting the current signal is more advantageous, since it is less susceptible to industrial RFI/EMI noise compared to the voltage signal. These transmitters are linearly calibrated to the signal produced by a thermocouple or RTD sensors and not to the actual temperature.

LTX-3000 require no separate power supply as it is powered by current drawn from the current loop itself and is thus intrinsically safe when used with appropriate barriers. It is very compact, economically priced and can be directly mounted inside standard heads of the thermocouple or RTD sensors. It can also be easily fitted inside the flame proof / weatherproof head or junction box. It is available for different thermocouples, RTD (Pt-100) duly calibrated for required temperature range with ZERO and SPAN adjustments for on site calibration. LTX-3000 is available in the standard size of 44mm OD and 26mm height (with the terminals) and center to centre mounting hole dimension of 33.0 mm so that it fits easily into the standard head.

The Transmitter is also available in DIN Rail compatible modules Model LTX-3000-D, in weatherproof enclosure Model LTX-3000-W, and in flameproof Model LTX-3000-FLP.
The Galavanically isolated versions are also available in DIN rail and weatherproof enclosure as the Model LTX-3000-DI and LTX-3000-WI respectively, where input and output are isolated.

Isolated versions are useful and recommended for the applications, where the transmitters are mounted away from the sensors. The isolation prevents further the RFI/EMI and ground line interference on the 4-20mA signal loop.


Features :

• Two wire design (supply and output on the same lines).
• Accepts RTD (Pt-100) / thermocouple / millivolt input.
• (4-20) mA non-isolated and isolated output from the sensor.
• ZERO and SPAN adjustments for on-site calibration.
• Easily fits in std. thermocouple head (weather or flame proof or in explosion proof JB).
• Loop supply of 12 to 36VDC (with loop continuity LED)
• Saturation or open sensor current limited to 25mA.
• Reverse polarity protection.
• Available in both head mount and DIN rail mount.

New model LTX-3000-H-2 is available for duplex sensors and can be fitted in the standard Head.

Applications :

• Carry thermocouple or RTD signals over long distance without noise and loss of accuracy.
• Eliminates use of costly compensating cable.
• Useful for converting other mV/Ohms signal to equivalent 4-20mA loop

Technical specifications :

Input Thermocouple, mV, RTD (Pt-100) or resistance signal from displacement, position or level sensor.

Subject to specified input (User should specify the required range).


(4-20) mA, two wire and loop powered 
(calibrated linearly to the input signal).

Accuracy ± 0.5 % to +/- 1% of the calibrated range or better including linearity, Hysterisis, and compensation error.
Calibration On site using ZERO / SPAN presets (user settable using a small screw driver)
Zero Adjustment : +/-25% of the range (20 Turns).
Span Adjustment : +/- 25% of the range (20 Turns).
Loop supply  (Vs)

24VDC nominal (12 to 36)VDC for non isolated versions and
24VDC +/- 10% for the isolated versions.

Loop Status The built in Red LED indicates the continuity status of the loop.
LED will not glow if the current loop is broken.
Loop Resistance

600 Ohms @ 24VDC (loop supply dependent).

Max. Load Resistance RL Max = (Vs-12V) / 20 mA.

Input and Output are Galvanically isolated (2KV) for isolated models

Burn Out Detection The output shall saturate > 20mA (max. 25mA @ 24VDC loop supply)
Operating Temp. 10 oC - 70oC
Mounting LTX-3000-H : In Standard or Flameproof head,
LTX-3000-D and DI : On 35 mm DIN rail.
LTX-3000-W and WI : on-field or on site on the wall using 4 screws.


LTX-3000-H : 44 Dia. x 26 mm (H)
LTX-3000-D and DI: 22 x 75 x 100 mm.
LTX-3000-W and WI : 80 x 80 x 57 mm.

Connection Diagram LTX-3000-H and LTX-3000-D :