Field-installation type ORP meter

HORIBA's long-selling water quality meter that excels in both indoor and outdoor applications.

Suitable for managing neutralization reaction processes such as aeration tanks and denitrification tanks. We offer a wide range of cleaning devices to accommodate a variety of samples.

Division: Process Water
Manufacturing Company: HORIBA Advanced Techno Co., Ltd.

Comprehensive range of cleaning devices.

A diverse lineup of cleaning devices are offered.  Particularly, ultrasonic cleaners are advantageous as they do not require water or air, making them convenient for retrofitting existing HO-200 installations on site. The drop-in type of cleaning device, which fits into a holder, offers ease of maintenance.

Product nameORP meter
Combined sensorORP electrode
Measurable rangeORP−2000 mV to 2000 mV (display range: −2200 mV to 2200 mV)
Temperature0℃ to 100℃
  • Display range (the sensor types are detected automatically):
    −10℃ to 110℃
  • Display range (the sensor types are input by manually):
    −20℃ to 130℃
PerformanceORPRepeatabilityWithin ±5mV (response for equivalent input)
LinearityWithin ±5mV (response for equivalent input)
TemperatureRepeatability±0.3℃ (response for equivalent input)
Linearity±0.3℃ (response for equivalent input)
Number of output point2 (the negative terminals for transmission outputs are internally connected at the same electric potential)
Output type4 mA to 20 mA DC: input/output insulation type
Load resistanceMax: 900Ω
LinearityWithin ±8 mA (output only)
RepeatabilityWithin ±0.02 mA (output only)
Output rangeOutput 1ORP: Selection from preset ranges or free range setting within measuring range.
Output 2Temperature: Free setting within a range between −20℃ and 130℃
Occasional out for errorHold or burnout to either 3.8 mA or 21 mA
Transmission holdSelectable from transmission signal is held at the latest value or preset value.
Contact outputNumber of output3
Output typeNo-voltage contact output
Contact typeRelay contact; SPDT (1c)
Contact capacity250 V AC 3 A, 30 V DC 3 A (resistance load)
R1, R2Selectable from upper limit alarm, lower limit alarm, ON/OFF control, currently holding of transmission output, and cleaning output (the contact is closed during alarm operation, opened normally and while the power is down).
FAILError alarm
(Closed in the normal state, opened in the failure state or while the power is down).
Alarm setting
  • Setting range: −2000 mV to 2000 mV
  • Delay time: 0 seconds to 600 seconds
Control setting
  • Setting range: −2000 mV to 2000 mV
  • Control width: 2 mV to 400 mV (±1 mV to ±200 mV)
Cleaning outputNumber of output points1
Output typeContact output with voltage (output of connected power supply voltage)
Contact typeRelay contact, SPST (1a)
Contact capacity250 V AC 0.5 A
External instrumentSolenoid valve for cleaning control
SettingsCleaning period0.1 hours to 168.0 hours
Cleaning time2 seconds to 600 seconds
Hold time2 seconds to 600 seconds
Timer accuracyWithin 2 minutes per month
Description of cleaning

One of the following operations.

  • Operation of internal timer only
  • Operation of internal timer and external input command
  • Enable the internal timer only when external input is active.
  • The cleaning trigger signal (the external trigger signal must be longer than 2 seconds).
Contact inputNumber of input points1
Contact typeNo-voltage "a" contact for open collector
ConditionsON resistance: 100 Ω max.
Open voltage: 24 V DC
Short-circuit voltage: 12 mA DC max.
Contact functionExternal input for cleaning
Communication typeRS-485
Signal type2 wires system, isolated from the input circuit
(not isolated from transmission circuit)
Applicable temperature
Platinum resistor: 1 kΩ (0℃)
Positive relation resistor with temperature:
500 Ω (25℃), 6.8 kΩ (25℃), 10 kΩ (25℃)
Element selection methodAutomatic temperature sensor type detection or manual selection
(no temperature element is selectable)
CalibrationORP adjust functionAdjust (offset adjustment): −200 mV to 200 mV
Span sensitivity correction: 0.500 to 1.500
Temperature calibration1 point calibration comparing reference thermometer
Self-checkElectrode diagnostic errorReference electrode impedance error (only applicable for differential circuit mode with a liquid contact electrode),
temperature sensor short-circuit, temperature sensor disconnection, and out of the temperature measurement range
Converter errorCPU, ADC, and EEPROM errors
Operating temperature range−20℃ to 55℃ (without freeze)
Operating humidity rangeRelative humidity: 5% to 90% (without condensation)
Storage temperature−25℃ to 65℃
Power supplyRated power supply voltage100 V to 240 V AC ±10% 50/60 Hz
Power consumptionMAX. 15 VA
OthersWith power switch for maintenance use
CE markingEMC    :EN61326-1
     Class A, Industrial electromagnetic environment
Safety   :EN61010-1
RoHS   :EN50581
      9. Industrial monitoring and control instruments
FCC rulesPart15 Class A
StructureInstallationOutdoor installation type
Installation methodMount on 50 A pole or wall
Protection codeIP65IEC60529, JIS C0920
Case materialAluminum alloy (coated with epoxy-denatured melamine resin)
Material of fittingsSUS304
Material of hoodSUS304 (coated with epoxy-denatured melamine resin)
Material of windowPolycarbonate
Display elementReflective monochrome LCD
External dimensions180 (W) mm × 155 (H) mm × 115 (D) mm (excluding mounting brackets)
MassMain body: approx. 3.5 kg, Hood and fittings: approx. 1 kg
  • *1:  :The standard for effect on the reading by the electromagnetic field of the radiated radio frequency and by the conducted interference is within the measured ORP value ±15 mV.
  • *2  : When the sensor cable, the transmission cable, or the contact input cable is extended to 30 m or longer, the surge test specified in the EMC directive for CE marking is not applied.



An arrester (spark over voltage: 400 V) is implemented for transmission output, contact input, and communication. However, use a most suitable surge absorption element on the connection lines in accordance with the ambient environment, the situation of equipment installed, and the externally connected equipment.

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