Chlorine Dioxide

HydroACT Series

The HydroACT Reagentless Chlorine Dioxide Analyzer is one of our online disinfection monitoring solutions. Just like with the other HydroACT series products, our Chlorine Dioxide (ClO2) sensor is simple to install, and extremely reliable. The membrane covered probe is exceptionally stable for chlorine dioxide measurement, and requires no zero calibration. The vented flow cell allows for ideal sample flow to give the best detection results. Not needing reagents, the system requires minimal maintenance, and hence has lower overall lifetime costs than competitors’ products. The analyzer can be used for simple monitoring, as well as for controlling the Chlorine Dioxide dosage and maintaining the target residual.

HydroACT analyzers and controllers offer versatile solutions for your disinfection monitoring needs, with the flexibility to accept additional sensors, as well as offering expandable I/O, and PID control loops.

  • Description

    The Chlorine Dioxide Analyzers can be used for whatever water applications where chlorine dioxide residuals need to be monitored and/or controlled. They consist of a HydroACT multi-parameter analyzer, a chlorine dioxide probe sensor, and a sample flow cell.

    There are options for the HydroACT configurations depending on how many sensor inputs are necessary, output and communication needs, and control requirements.

    Standard flow cells are for a single probe. There are also options for two and three probe flow cells.

    Standard Features

    • Includes analyzer, chlorine sensor, flow cell, 1 analog output, 1 year consumables
    • Accurate chlorine dioxide measurement
    • No moving parts, no reagents
    • Event logging

    Optional Features

    • Expandable sensor inputs and I/O
    • Color display and data-logging with microSD card download
    • Modbus or PROFIBUS communications
    • Chemical feed control capability (e.g. PID)


    • Lower total cost of ownership
    • Easy set up and maintenance
    • Intuitive menu and programming functions
  • Specifications

    The HydroACT Chlorine Dioxide Analyzer standard configuration includes version HA2 analyzer, 1 sensor, 1 analog output, and 1 year
    consumables. Optional features include relays, digital inputs, digital comms, expanded number of sensor inputs and analog outputs, color display, and data
    download capability. Maximum I/O capabilities and certain features are specific to the different versions of HydroACT as detailed below.

    HydroACT Features HA2 HA4 HA8
    Sensor limit* 2 4 8
    Analog output limit* 2 4 8
    Relay limit* 4 8 16
    Digital Input limit* 4 8 16
    On/Off threshold control optional optional optional
    Advanced control (e.g. PID) optional optional optional
    Color display
    Data logging and download
    Remote (Internet) access optional optional
    PROFIBUS, Modbus optional optional

    *Optional configuration limits. See above description for standard configuration of analyzer version & I/O setup. Optional configurations must be specified.

    Sensor Options Free Cl, Total Cl, Cl Dioxide, Chlorite,
    Ozone, ORP, pH with Temperature, DO,
    Conductivity, SCM, UV254 Organics,
    TSS/NTU, Particle Counter
    Available Output Types Universal (0-20mA, 4-20mA, 0-10 VDC)
    Relays (optional) SPST electromechanical relays rated for 380 VAC, 6A max.
    Alarms & Thresholds: user-configurable alarms and 2 user-configurable thresholds (for control)
    Chemical Feed Control (optional) HA4 & HA8 only – PID, Feed Forward, Flow Proportional, Timer – multiple loops
    Communication (optional) Modbus ASCII/RTU (RS485), Modbus TCP (Ethernet), Profibus DP
    Data Logging (optional) Customizable data logs. 1 million records can be logged internally, and downloaded to MicroSD card.
    Enclosure ABS flame retardant, IP65, Nema 4X
    Display 4.3”, 480×272, 24 bit, grayscale
    Optional: color (HA4 & HA8 only)
    Dimensions HA2 & HA4 – 9.0” W x 12.2” H x 4” D
    (230 mm W x 309 mm H x 1035 mm D)
    HA8 – 18.0” W x 12.2” H x 4” D
    (460 mm W 309 mm H x 1035 mm D)
    Weight HA2 & HA4 – 4.5 lbs (2 kg)
    HA8 – 9 lbs (4 kg)
    Warranty 12 months from date of purchase

    Chlorine Dioxide Sensor Probe

    Type Membrane-covered amperometric three-electrode system
    Measured Chlorine Dioxide
    Probe Ranges 0.01 – 2, 0.01 – 5, 0.01 – 10, or 0.01 – 20 mg/L
    Resolution 0.01 mg/L (ppm)
    Reproducibility ±5%
    Stability -2% per month (without calibration)
    Working Electrode Gold cathode
    Counter Electrode Stainless steel anode
    Reference Electrode Silver/silver halide
    Flow Rate 15 to 60 L/hr.
    Temperature Range > 41° up to < 113° F (> 5 up to < 45° C)
    Temperature Compensation Automatically by integrated thermistor (ATC)
    pH Range pH 2 – pH 11
    Permissible Over-Pressure 7.25 psi (0.5 bar)
    First Polarization Time 120 min.
    Re-Polarization Time 30 min.
    Zero-Point Adjustment Not necessary
     Calibration At the device, by analytical determination
     Housing Material PVC, silicone, polycarbonate, stainless steel
     Dimensions Diameter approx. 0.98 in., length 6.89 in.
    Replacement Intervals
    Membrane: Annually (approx.) depending on water quality
    Electrolyte: 3 – 6 months depending on water quality
     Interferences Ozone and chlorine. Surfactants are partially tolerated

    *Not suitable for measuring or controlling for dechlorination. Recommended to have a chlorine residual of at least 0.10 ppm at all times.

  • Applications

    Water treatment

    • Disinfection monitoring
    • Chlorine Dioxide dosage control

    Cooling towers
    Swimming pools
    Paper machine system microbial control
    Legionella control
    Food washing

  • Downloads

  • News

  • Videos

    Video Testimonial: Chlorine Monitoring in Distribution

    Video Testimonial: Chlorine Monitoring in Distribution

    Having accurate, reliable, and real-time chlorine monitoring, both in the water treatment plant, and in the distribution system, is critical.

    Watch Video

    Chemtrac Chlorine Analyzer

    Chemtrac Chlorine Analyzer

    The Chemtrac Chlorine Analyzers take online disinfection monitoring to a new level of rleiability. They are accurate, pH independent, and offer a low cost of ownership with a full 12 months between maintenance events. These analyzers are suitable for regulatory reporting purposes when used in compliance with EPA Method 334.

    Watch Video

    Chemtrac Chlorine Sensor Assembly and Setup

    Chemtrac Chlorine Sensor Assembly and Setup

    Properly assembling the chlorine sensor is critical to the operation of the chlorine analyzer. This video demonstrates the appropriate way to set up the probe with the electrolyte, and the membrane cap. And this procedure also applies to other membrane-covered sensors, such as total chlorine, chlorine dioxide, chlorite, and ozone.

    Watch Video

    Chemtrac Chlorine Sensor Flow Cell Setup

    Chemtrac Chlorine Sensor Flow Cell Setup

    The chlorine sensor flow cell is designed to direct the proper sample flow past the membrane in order to ensure accurate and consistent results. This flow cell is also used with a variety of membrane-covered sensors such as free chlorine, total chlorine, chlorine dioxide, chlorite, and ozone.

    Watch Video

    WTP Prefers “Reagentless” Chlorine Analyzers

    WTP Prefers “Reagentless” Chlorine Analyzers

    A Water Treatment Plant in Auburn, AL has the need to monitor free chlorine onsite, as well as at remote locations in the distribution system, where they do not want to have to use reagents. They fist ordered a Chemtrac Reagent-less Free Chlorine analyzer in 2009, and have since purchased several more for other monitoring locations.

    Watch Video

Connect With Us

Call Us

800.442.8722 or 770.449.6233

Meet Us

1555 Oakbrook Drive
Suite 100
Norcross, GA 30093