Water Quality Instruments and Probes

Model 6537A, 6528C, 6528B and 7422A

  • Overview

    Water quality measurements are performed for water in streams, rivers, lakes and the groundwater system, using boreholes. There are several different measures for water quality, like electro conductivity (EC), pH (PH), and dissolved oxygen (DO). Unidata’s range of water quality monitoring instruments and probes consists of:

    The Unidata’s 6537 Starflow QSD SDI-12 and Modbus Instrument has a 4 electrode electro conductivity instrument (EC) included for measuring the quality of the water. Water quality is measured on an ongoing basis and this parameter can be recorded along with velocity and depth to better analyse the nature of the water in open channels and pipes. Conductivity is a very important water quality measure and any spike in the conductivity is a strong indicator of a pollution event.

    pH double junction probe 6528 has a rugged design and utilises a double-junction reference system to minimise the effects of contamination due to clogged pores or ingress of the sample. The probe is designed as a low power instrument and includes built-in conditioning electronics for direct connection to a datalogger.

    The 6528 pH probe consists of a pH sensor with a voltage output that varies proportionately to the hydrogen ion activity between a reference electrode and an electrode immersed in an alkaline (basic) or acidic solution. These advanced electrodes feature proven flat tip technology which virtually eliminates deposits that can foul the electrode, significantly reducing necessary maintenance.

    Each electrode has a built-in potential matching pin. With this feature, electrode fouling caused by a ground loop current through the reference of the sensor is a thing of the past. These electrodes have been engineered with a replaceable battery to power the amplifier. This feature adds life to the electrode and aids in troubleshooting. With this feature, electrode fouling due to ground loop

    The dissolved oxygen probe 7422 is a galvanic measuring element that produces a millivolt output proportional to the oxygen present in the medium it is placed in. It consists of an upper part with the cathode, anode and cable, and a cap with membrane and electrolyte.

    Oxygen diffuses through the membrane onto the cathode, where it reacts chemically and then combines with the anode. This chemical process develops an electric current, which flows through a built-in resistor. The resistor converts the current (microamps) into millivolts. This millivolt signal is led to the data logger via a two-core cable.

    The probe is virtually maintenance-free, requiring only that its membrane be kept reasonably clean. The anode remains fully active through its lifetime of several years. The membrane is very robust and can be wiped clean with a cloth or paper. It is recommended that the membrane be cleaned from time to time to ensure maximum reliability.

    Starflow QSD Ultrasonic Doppler Velocity, Depth and Conductivity Instrument
    pH probe and Disolved Oxygen probe

  • Specifications

    6537 Starflow QSD Water Velocity, Depth, Temperature and Conductivity Instrument
    6537 Starflow QSD

    6528 pH Double Junction Probe
    Material: PVDF Body
    Size: Diameter 25 x Length 141mm
    Weight: 400g including cable
    pH Range: 0-13
    Junction: Double
    Junction Type: Teflon
    Electrolyte: Polymer
    Pressure: 6bar (87 PSI)
    Temperature Range: -5° to 80°C
    Cable: 5m of 2 core

    7422 Dissolved Oxygen Probe

    Material: PVDF Body
    Size: Diameter 58 x Length 59mm
    Weight: 450g including cable
    Range: 0-50mV (2.5 to 5mV per ppm mg/l)
    Output impedance: 1kΩ
    Type: Galvanic cell, self-polarising, self-temperature-compensating
    Temperature Range: 0 to 40°C
    Pressure: Submersible to 100m
    Cable: 7m

  • Ordering Information

    Model Description
    6537A Starflow QSD and EC SDI-12 and MODBUS Instrument
    7422A Dissolved Oxygen Probe
    6528C Double Junction, Teflon, pH Probe
    6528B Double Junction, Teflon, ORP Probe

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    • Documents