SCM 31x

Transmitter pH and ORP/conductivity/DO


  • Converting pH and redox signal in 4-20mA (SCM 311)
  • Converting conductivity signal in 4-20mA (SCM 312)
  • Converting DO signal in 4-20mA (SCM 313)
  • Span and ofset calibration
  • Temperature compensation
  • Galvanic input/output isolation


SCM 311/312/313 is industrial measurement converter who has current signal 4-20mA as his output signal, equivalent to voltage of pH and ORP/conductivity/ DO input signal.

Transducer has a galvanic input/output isolation, wide range power supply, high input impedance, has a span and offset calibration feature, and manual or automatic compensation. Housing is water resistant and plastic for wall and panel mounting, it's dimensions are 115 x 90 x 56 mm with IP65 protection.

Device calibration is performed using alphanumeric LCD display with 16 characters in two rows and four buttons keyboard.

Galvanic input/output isolation excludes the possibility of interferences from different kinds of earth connection. This is particularly important feature, since two different earth connections can differ for couple of hundreds of Volts.


SCM 311/312/313 pH and ORP/conductivity/DO transmitter is used for assertive measurement of pH and redox/conductivity/DO in following systems:

  • Waste water management systems,
  • Production process automatisation (e.g. in chemical and food industry), and
  • Remote tracking of river and lakes pollution
  • Field data readout using laptop.


pH input (SCM 311)Galvanic pH probe:
two-probe system
Resolution 0.01pHAccuracy 0.02pH
ORP input (SCM 311)Standard platinum probe
Resolution 1mV
Accuracy ±2mV
Conductivity input (SCM 312)Standard conductivity probe
Resolution 0.01µS
Accuracy 0.02µS
DO input (SCM 313)Galvanic probe for DO
Resolution 0.1%
Accuracy 0.1%
Input resistivityHigher than 1012Ω
Temperature inputinternal sensor, 100Ω RTD, 1000Ω RTD,
manual input
Resolution 1°C
Accuracy ±1°C
Transmitter voltage13V nominal
Measuring rangeSCM 311:  0.00 to 14.00 pH
0 to 1500mV (ORP)
SCM 312: 0.00 to 20.00mS
0.000 to 2.000mS
0.0 to 200.0µS
0.00 to 20.00µS
SCM 313: 0-100% saturation
Temperature range: -20 to 110°C
Measuring cycle0.4s
A/D converterSAR 12-bits
Current output4-20mA, alarm value 3.5mA/20.5mA
Resolution 0.005mA
Accuracy ±0.05mA
Working temperature-10°C to 50°C
Humidity5 to 95%, without condensing
DisplayLCD 8 digits 9mm
Power supplyFrom the loop (4-20mA), loop voltage 13 to 32Vdc
Dimensions90mm (H) x 115mm (W) x 56mm (D)
AssemblyScrew plug, max 2.5mm2
Weightcca 500g


SCM 31110201

Isolated industrial pH and redox signal converter to 4-20mA

SCM 31210202

Isolated industrial conductivity signal converter to 4-20mA

SCM 31310203

Isolated industrial DO signal converter to 4-20mA


*Minimum functionality kit needs to include the device and an appropriate sensor probe. Please note that all accessories are sold separately.


*Please note specifications for the sensors compatible with our devices:

SCM 311 sensor specification:

  • pH: galvanic pH electrode, combined or two electrode system
  • ORP: standard platinum electrode
  • external temperature probe: PT100/PT1000

SCM 312 sensor specification

  • conductivity: standard conductivity electrode
  • external temperature probe: PT100/PT1000

Product Documents