2-Wire 24VDC pH/ORP Transmitter / Analyzer PH202
Notice: This product was discontinued on Mar 1, 2012. See this replacement product:

Flexibility, low maintenance and low installation costs are among the benefits of the EXA PH202 pH transmitter. Designed to meet the exacting requirements of measuring pH and ORP in the modern industrial environment, it contains many features to ensure peak precision whatever the application.

This 2-wire (loop powered) transmitter is housed in a robust IP65 field mountable case. The need for expensive cabling is minimized, and an IS version is available for hazardous area duty.


  • Universal pH/ORP, dual high impedance inputs
  • On-line sensor checking
  • HART, Profibus, or Foundation Fieldbus communications interface
  • Event logbook in software
  • Process temperature compensation
  • Differential input amplifier with equipotential screening
  • Freely configurable ITP, slope and asymmetry
  • Easy to use EXA control panel
  • Password protection for all levels of software
  • Intrinsically safe versions – FM, CSA, and CENELEC approval
Measuring principle Glass electrode method
Input ranges pH: -2 to 16 pH
ORP: -1500 to 1500 mV
rH: 0 to 55 rH
Temperature: -30 to 140℃
Output ranges pH: Min. 1 pH, Max. 20 pH
ORP: Min. span 100 mV, Max. span 3000 mV
rH: Min. 2 rH, Max. 55 rH
Temperature: Min. 25℃ , Max. 200℃
Output Signal 4 to 20 mA DC loop powered, isolated from input
With the possibility of 21 mA "FAIL" signal (burn up) and 3.6 mA (burn down when HART or distibutor comm. is non-used), 3.9 mA (burn down when HART or distributor comm. is used).
Temperature compensation Range: -30 to 140℃ (for 8k55 sensor -10 to 120℃ ).
Sensor types: Pt100, Pt1000, 3 kΩ RTC, 5.1 kΩ PTC, 8.55 kΩ NTC, 350 Ω PTC, 6.8 kΩ PTC, 10 kΩ PTC. Automatic or manual compensation to Nernst equation. Process compensation by configurable coefficient. Adjustable ITP (Iso-thermal point of intersection).
Calibration Semi-automatic, using tables in transmitter for pH 4, 7 & 9 buffer solutions, or using user-defined tables, with automatic check of measurement stability.
Manual, using standard sample, by correcting reading to value of standard.
Calibration by slope and asymmetry potential setting. (IEC60746-2)
Communication HART®, PROFIBUS-PA, FOUNDATION Fieldbus H1
Ambient temperature -10 to 55℃
Humidity 10 to 90 % RH (Non-condensing)
Display Custom liquid crystal display, with a main display of 3 1/2 digits 12.5 mm high.
Power supply Nominal 24 volt DC loop powered system.
PH202G: 17 to 40 V

The specifications are expressed with simulated inputs.

pH Linearity: ±0.01 pH
Repeatability: ±0.01 pH
Accuracy: ±0.01 pH
ORP   Linearity: ±1 mV
Repeatability: ±1 mV
Accuracy: ±1 mV



The lifetime of a pH sensor has a significant impact on the overall annual costs of a pH measuring loop. Optimizing four key factors will decrease these costs and optimize process control and overall plant efficiency.


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