9184 sc Amperometric analyzer for active chlorine

Description

The Hach Lange 9184 sc sensor is ideal for monitoring active chlorine concentrations in drinking water, chlorination processes, demineralization systems, wastewater treatment or cooling water, thanks to its range of 0 to 20 ppm. A minimum detection limit of 5 ppb (0.005 mg/L as HOCl) allows the 9184 sc to stand out from other sensors at near-zero chlorine readings.

The 9184 sc Comprehensive Active Chlorine Measurement System is supplied pre-assembled on a panel. To get started, you just need to install the panel in the desired place, insert the sensors and connect the controller. The membrane system of the sensor indicates that no reagents are used for measurement. Maintenance is minimal and the system is shipped with maintenance accessories that are sufficient for two years.

The sensor measures continuously and transmits the data to the controller. Depending on the model, the 9184 sc sensor can measure:

• only hypochlorous acid (HOCl - active chlorine)
• HOCl with acidification
• total free chlorine (TFC), measuring temperature, pH and HOCl to calculate hypochlorite ion (OCl-). The sum of HClO and OCl gives the total free chlorine value.

Available options include:

• Acidification Unit (LZY051) - Used when sample pH exceeds 7.5. The fully programmable device sets the pH of the sample to a range of 5.5 to 6.5. It can be used intermittently or continuously.

Principle of operation

The amperometric method is used to measure HOCl concentration. The membrane allows selective diffusion of HOCl molecules to the amperometric sensor. The measurement is pH and temperature compensated.

The amperometric sensor consists of:

• the gold working electrode (cathode) on which the main reaction occurs
• silver reference electrode (anode)
• electrolyte KCl
• microporous membrane selective for HOCl

The HOCl molecules in the sample diffuse through the membrane into a thin region containing the electrolyte between the membrane and the cathode.

A constant potential is applied to the working electrode. On a silver electrode (anode), silver is oxidized to Ag +. Reduction of HOCl at the cathode generates a current that is directly proportional to its partial pressure in the sample.

Electrochemical reaction and membrane diffusion are temperature dependent. The measuring cell contains a temperature sensor for automatic temperature compensation.

In the acidification version, the analyzer offers the ability to measure samples with a high pH value. The pH value is kept constant between 5.5 and 6.5 by the continuous addition of an acid solution. At these pH levels, all ClO- ions are converted to HOCl, allowing the sensor to measure active chlorine.

Specifications

• Measurement range: 0 to 20 ppm (mg/L) HOCI
• Minimum detection limit: 5 ppb or 0.005 mg/L HOCl
• Accuracy: 2% or ± 10 ppb HOCl
• Response time: 90% in less than 90 seconds
• Measurement interval: continuous
• Minimum flow rate: 14 l/h (200 to 250 ml/min) automatically adjusted by the cell
• Pressure range: 0.1 to 2 bar in flow cell
• Sample temperature: 2 °C to 45 °C
• Temperature compensation: automatic in the sample temperature range
• Sample pH: 4 to 8 (acidification block available for pH above 8)
• Measurement technology: amperometric / membrane
• Interference: no interference from chloramines, while chlorine dioxide and ozone affect measurements.
• Mounting: flat vertical surface (panel, stand, etc.)
• Connections: sampling line: 1/4 in. OD, drain line: 1/2 in. ID (supplied)
• Electrode materials: gold cathode / silver anode, measuring cell: acrylic, sensor body: PVC
• Dimensions: 299 x 250mm