T703 Two-Wire Transmitter

DC Input Isolating, Field Configurable Two-Wire Transmitter – T703

Product Description

T703 Two-Wire Transmitter

The T703 Two-Wire Transmitter has 16 overlapping input ranges which are field selectable via top-accessed DIP switches (see Table 1). The T703can accept input voltage spans from 20mV to 200 volts and input current spans from 1mA to 50mA. Bipolar selection modifies the unipolar range to include a negative offset (e.g. 200V becomes ±100V). The T703 provides 1000Vrms of transformer-coupled isolation and 120VAC continuous input overload protection. The top-mounted super bright LED illuminates when the loop current is above 3.3mA. Standard surface mount RFI filters reject walkie-talkie interference and noise. Current output is in proportion to the selected voltage or current input.

The T703 has 80% zero “turn-up” and 80% span “turn-down” adjustments within any user-selected input range. For example, Range 11 of Table 1 specifies 0 to 100V with a minimum span of 20V (100V – 20V = 80V, or 80%). This 80% adjustability allows the user to field-calibrate the unit from the maximum (0 to 100V) down to any minimum (20V) span (e.g. 25V to 45V) within the selected 0 to 100V range. The same is true in any user-selectable range: all spans are field adjustable from 20% (minimum span) to 100% of the specified range.


The T703 is useful in any application requiring an isolated two-wire loop current from a DC source. Typical applications include long distance signal transmission and the elimination of ground loops. The output of the T703 can be used to drive a digital meter for direct display, or to interface with a computer for monitoring and control applications.

The model T703 is FM approved for intrinsically safe operation, entity, Classes I, II, III, Division 1, Groups A-G and Nonincendive, Class I, Division 2, Groups A-D hazardous when installed per manufacturer’s drawing 790-0028-00.

The model T703 is CSA approved for intrinsically safe operation for Class 1, Division 1, temperature code T3C, Groups A, B, C and D hazardous locations when installed per manufacturer’s drawing 790- 0025-00. Refer to model F703 for NEMA 4, FM/CSA/CENELEC approved explosion-proof housing.


Input Span Range (Min/Max)   

See Table 1.

  • Note: Bipolar span selection will move unipolar range to reflect negative offset (e.g., 20mA = ±10mA)


Input Inpedance 

  • Ranges 1-4: 5M Ohms, typical
  • Ranges 5-12: >200k Ohms, typical
  • Ranges 13-16: 20 Ohms, typical


Output Span (fixed)   



Minimum Output Current   

3.3mA, typical


Maximum Output Current   

24mA, typical


Supply Voltage Range   

13 to 80VDC


Maximum Change In Supply Voltage Effect 

0.05% of Span


Maximum Changes In Load Effect   

0.05% of Span


Loop Voltage Drop   

13VDC @ 20mA


Output Current Limiting     

  • Active: 27mA
  • Fused (fixed): 0.25A


Entity Parameters   

  • VOC = 33VDC, ISC = 178.5mA,
  • CI = 12nF, LI = 0uH



  • Zero: ± 0.02% of span/°C, max. (±0.05%, bipolar)
  • Span: ±0.03% of span/°C, max.



  • Overall (Includes best straight line Linearity, Hysteresis & Repeatability @ 25°C): ±0.2% of any adjusted span, max.
  • Linearity: ±0.1% of range
  • Hysteresis & Repeatability: ±0.05% of range
  • Settability: ±0.05% of range

Zero Adjustability   

80% “turn-up” of span (max)


Span Adjustability   

80% “turn-down” of full-scale range (max)


Response Time (63% response)

100ms, max.


Output Ripple

0.1% of span, rms, typical 0.5%, max.


Normal Mode Rejection

16dB @ 60Hz


Common Mode Rejection

60Hz: 80dB, DC: 120dB



  • 60Hz: 1000Vrms
  • DC: 1000VDC


RFI Effect (1.5W, 470MHz at 1.7 ft)

<1% of span error



1000Vrms maximum, input to output, input to case,output to case.


Temperature Range

  • Operating: -40 to 80°C
  • Storage: (-40 to 176°F)





Agency Approval

  • FM approved intrinsically safe for hazardous locations, certificate No. J.I. 1V4A5.AX.
  • CSA approved intrinsically safe for hazardous locations, Class I, Division I, Groups A-D, when connected in accordance with manufacturer’s drawing 790-0025 (File No. LR42272-40).
Ordering Information
1. Specify: Model: T703-2000
2. Option: U (see text)
3. Optional Custom Factory Calibration: Specify C620 with desired input and output range.
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