Hach Controllers SI792 for Electrochemical Applications


Hach Controllers SI792 The analysis of electrochemical parameters is the basis for all process analysis. This is a core competence of HACH LANGE, which has more than 30 years of experience in the analysis of liquids. SI792 2-wire and SI794 4-wire controllers offer long-term operations with a high level of measurement accuracy. The Hach Controllers SI792  is an intrinsically safe version, which is ideal for use in zone 1 explosion risk areas, e.g. in production plants.

Hach Controllers SI792 for Data and measurement safety

The versatile controllers can be used for ultrapure water, process water, drinking water and wastewater applications. Hach Controllers  SI792 supports communication with HART, PROFIBUS PA and FOUNDATION FIELDBUS. The universal power unit of the SI794 makes it suitable for use with any power supply. The long-term reliability of both controllers is ensured by their clearly organised operating structure and the secure protection of data and settings.

Hach Controllers SI792

The Features of SI792

  • Analysis of liquids in industry and the wastewater treatment sector
  • SI792 for use in explosion risk areas
  • Rugged and durable, thanks to high-quality materials

Hach Controllers SI792 for Controllers, Sensors, and Fittings

The safety concept of the SI controller starts with the clearly segmented and non-reflecting display. Large characters and symbols show the measured value, the temperature, and the sensor and controller status. The large keys help eliminate operator error. The smileys provide information about the sensor status:

  • Whether it is functioning properly
  • Must soon be serviced or replaced,
  • Needs to be replaced immediately.

In addition, a LED signals:

  • That a fault requiring rapid intervention has occurred.
  • A hold status, during which the measurement data cannot be transmitted and the sensor can be cleaned or calibrated.

The calibration can be carried out very conveniently, thanks to the menu guidance and automatic reminder function. Data and settings are effectively protected through security codes and administrative rights. Although the electronic system is enclosed to protect it, the cables can be accessed without difficulty for the purpose of installation.

Technical Data

  SI792 SI794
Power supply HART: 14–30 V DC (30 V DC max) FOUNDATION FIELDBUS, PROFIBUS PA: FISCO supply voltage 9–17.5 V DC; linear characteristic curve 9–24 V DC 24–230 V AC/DC; approx. 5 VA, 2.5 W; AC: 45–65 Hz
Communication HART (standard), FOUNDATION FIELDBUS H1 (optional), PROFIBUS PA (optional) ./.
Outputs 1 × 4–20 mA, electrically isolated 2 × 4–20 mA, electrically coupled
Explosion protection ATEX II 2(1)G Ex ia IIC T4, C1D2 or ./.
certificates C1D1 for FM and CSA
Alarm contact ./. Relay contact, potential-free
Limit values ./. Output through relay contacts R1 and R2; contacts potential-free but coupled together
PID process controller ./. Output through the relay contacts
Ingress protection rating IP 65
Display LCD: 7 segments with symbols
Main measured value display: character height 17 mm Temperature display: character height 10 mm
Alarm display Red LED for alarm or HOLD
Data retention Parameters and calibration data >10 years (EEPROM)
Type of mounting Wall, console, rail or stand (horizontal and vertical)
Electromagnetic compatibility (EMC) EN 61326, Emission: Class B (residential environment), Immunity: Industrial environment
Dimensions 1/2 DIN 144 × 105 mm (W × H × D); Weight: appro×. 1 kg

Conductivity sensors

The wide range of sensors assures flexible process and quality monitoring:

  • Precise 2-electrode sensors for ultrapure and drinking water
  • Low maintenance 4-electrode sensors with pollution compensation for versatile use with wide measuring range
  • Inductive sensors for non-contact measurement in highly polluted and aggressive media, e.g. acids.

Amperometric oxygen sensors

Reliable oxygen sensors are a prerequisite for optimal ultrapure water treatment and biological processes, e.g. in the food industry, power stations, and sewage treatment plants. The sturdy construction and smooth stainless steel surface of the O2 sensors make them easy to use and clean.

Electrodes for pH and redox

There is a wide choice of designs to satisfy the varied requirements for process, drinking and wastewater


  • Gel, polymer, or liquid electrolyte
  • Silt, hole, ceramic, or Teflon diaphragms
  • With or without an integrated temperature sensor.


  • Inductive conductivity sensors
    • Materials*: Polypropylene, PVDF, PEEK, PFA Teflon; with and without explosion protection for zone 0; Measuring range: 0.1–2,000 mS/cm
  • 4–electrode conductivity sensors
    • Materials*: Epoxy resin/graphite; with and without explosion protection for zone 0; Measuring range: 0.01–500 mS/cm
  • 2–electrode conductivity sensors
    • Materials*: Polyester, graphite, stainless steel; with and without explosion protection for zone 0;Measuring range: 0.01–20,000 μS/cm
  • Oxygen sensors
    • Material*: Stainless steel; with and without explosion protection for zone 0; Measuring range: 0.001–40 mg/l
  • pH/redox (ORP) electrodes
    • Materials*: Glass, platinum, gold, with and without explosion protection for zone 0; Measuring range: 0–14 pH; ±1,500 mV
  • Fittings
    • Materials*: Stainless steel, PVDF, polypropylene; as immersion, retractable and flow-through fitting

Source : www.hach.com

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