Define Instruments TM-2HL: Head-Mount Transmitter, non-isolated
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This non-isolated 2-wire in-head mount transmitter is specifically designed for RTD and thermocouple temperature applications, and has a 4-20mA current output. USB programming is hassle free – it takes just 2 minutes using our purpose-built software, and no calibration or power supply is required.


This is the market's first USB powered programmable DIN-mount transmitter from Define Instruments.
It is extremely easy to program by anybody from only the USB port of a PC and do not require additional power connected.

Your own technicians can program these easily and effortlessly on site or at your workshops.

Define Instruments's TM-2HL universal transmitter features:

  • 2-wire temperature transmitter (head mount, non-isolated)
  • Input: 3-wire RTD (Pt100/Pt100)
  • Output: 4-20mA loop
  • USB port for PC programming (requires TM-USB communications kit)
TM-2HL universal transmitter


Define Instruments’s TM transmitters convert the sensor input signal to a current or voltage output, where it can then be displayed or controlled by a variety of industry standard compatible devices. They accept a wide range of standard input types without the use of jumpers and are available in DIN-rail mount or head-mount casing.

A reusable USB communications kit can be added to enable PC interface, using purpose-built, windows compatible software.

Common Specifications
Configuration2-wire 420mA (loop powered)
Power supply9.5-36V DC
9.5-36V DCSupply voltage sensitivity< ±0.005%/V FSO
< ±0.005%/V FSOOutput load resistance700Ω at 24V DC (50Ω/V above 9.5V DC)
Maximum output currentLimited to <28mA (Emission mission & immunity)
EMC complianceEmissions (EN 61326). Immunity (EN EN61326). Safety (EN 61010-1).
Accurate to<±0.03% FSO typical
Ambient drift<±0.003%/°C FSO typical
Noise immunity125dB CMRR average (2.0kV DC limit)
R.F. immunity<1% eff ect FSO typical
Response time400msec typical (10–90% 300msec typical)
Operating temperature–20–+65°C
Storage temperature–20–+100°C
–20–+100°COperating humidity5–85%RH max (non-condensing)
CasingHead mount - 44 x 44 x 23mm (H x W x D)
Thermocouple Input Specifications
Thermocouple typesB, E, J, K, N, R, S, T
B, E, J, K, N, R, S, TUSB programmable zero0–±99% of the span
Input impedance1MΩ min
Thermocouple lead resistance100Ω max
Cold junction comp.–20–+90°C
AccuracyE, J, K, N, T: < ±2°C. B, R, S: < ±3°C.
Temperature driftE, J, K, N, T: < ±0.05°C. B, R, S: < ±0.2°C.
Sensor break output driveFunction high upscale/low downscale
CJC error< ±1°C
RTD Input Specifications
RTD inputPt100 or Pt1000 DIN 3-wire type (2-wire can be used with off set calibration)
Sensor current0.15mA nominal
0.15mA nominalLead wire resistancePt100: 10Ω/wire max. Pt1000: 5Ω/wire max. 0.02% FSO off set error per Ω of lead resistance.
Accuracy≤ 0.3°C
USB programmable zero0–±99% of the span
USB programmable span–200–+850°C
Sensor break output driveFunction high upscale/low downscale
Linearity (Pt100)0.02% FSO for span inputs ≤200°C. 0.1% FSO for span inputs ≤850°C
Linearity (Pt1000)0.02% FSO for span inputs ≤200°C. 0.2% FSO for span inputs ≤520°C
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