Loop Powered RTD Transmitter
Model RTT

Model RTT is a 2 wire loop powered resistive temperature transmitter (RTT) which measures resistance changes as a function of temperature. It will convert 2 or 3 wire RTD (Resistive Temperature Detector) input to a 4 to 20 mA DC current. The output current is linearized with temperature. It has very high accuracy, extremely low drift, very low temperature coefficient, excellent repeatability and long term stability.  The features of the case include a central hole for easy spring loading of tube, insulating barriers between terminals to prevent shorts even under condensation environment. It can be mounted in a connection head or a flat surface using the two mounting holes provided.  

Input RTD Type:
Platinum RTD, Pt100, 100 ohm at 0oC, TC 0.00385/ oC.
Input Connection:
3-wire connection is standard for platinum lead wire compensation.
Output Current: 4 to 20 mA. Accuracy at 23 oC: See the Table below

Accuracy at 23 oC: See the Table below.
  Model Temperature Range Calibration Accuracy Linearity

Single Range

RTT-50    0 to 50 oC 0.05% of F.S.  0.05% of F.S.
RTT-100 0 to 100 oC 0.05% of F.S. 0.05% of F.S.
RTT-200 0 to 200 oC 0.05% of F.S. 0.05% of F.S.
RTT-N200 -200 to 50 oC 0.05% of F.S. 0.05% of F.S.


RTT-TN50 -50 to 50 oC/ -50 to 
100 oC / -50 to 150 oC
0.05% of F.S. 0.1% of F.S.
RTT-T200 0 to 50 oC / 0 to 
100 oC / 0 to 200 oC
0.05% of F.S. 0.1% of F.S.
RTT-T500 0 to 300 oC/ 0 to 
400 oC / 0 to 500 oC
0.05% of F.S. 0.1% of F.S.
Note: Accuracy not including the error of RTD probe.

Adjustability: RTD transmitter is pre-calibrated at factory. Due to the long-term stability, large range adjustment is not necessary. Zero and span each are adjustable approx. +/- 5 % of span.

(Usually when the transmitter has large adjustment range, the temperature coefficient and drift would be larger.) 

Electrical Response Time: Under 1 milliseconds.

Common Mode Rejection: 80 dB typically.

Guaranteed Operating Temperature:
-20 to +85 oC

Temperature Coefficient: Typical +/- 30 ppm/ oC, Maximum +/- 100 ppm/ oC

Storage Temperature Range: -40 oC to 100 oC

Relative Humidity: 0 to 90% RH (non-condensation inside the case)

Power Requirements at RTT terminals: DC 12.8 V to 26.4V, 1 W.

Maximum Output Current: 32 mA

Insulating Resistance between Terminal and Case: > 50 Mohm

Plastic Case Size: Dia. 46 mm, Height:  22 mm

Connection: Terminal blocks.

Weight: 35 gram

Case Dimensions and terminal blocks:
See Fig. 1.

Connection: Connect the RTD sensor, wires, current sensing resistor with volt-meter, or current meter with current limiting resistor as shown in Fig. 2.

Load Resistance Selecting Range: In order to reduce the power dissipation and the drift of transmitter, the load resistance range is suggested as follows:

Load Resistance <  [ Supply Voltage (V) 12.8 V] / 0.02 A
Load Resistance >  [ Supply Voltage (V) 15 V] / 0.02 A

Model RTT is pre-calibrated at the factory. In case there is a need to recalibrate, follow the steps below:
  1.  Connect Model RTT as in Fig. 2. Replace RTD with a precision decade              resistance box or RTD calibrator. 
  2. Warm-up for 15 minutes.
  3. Set the resistance value to the low end of the temperature range, and adjust the Zero potentiometer to get 4.000 mA output.
  4. Increase the resistance value to full scale and adjust the Span potentiometer for 20.000mA output.
  5. Repeat step 3 and step 4 until both levels are accurate, for there is a very small interaction between the zero and span control.
The RTT series carry a limited warranty of 2 years.  In the event of a failure due to defective components or workmanship, during the 2 years warranty, the transmitter will be repaired or replaced at no charge.