Water Quality Instruments and Probes

Model 6536E, 6536P-2, 6528C, 6528B and 7422A

  • Overview

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

    The 6536E Water Electroconductivity Instrument with 6536P-2 Conductivity Probe measures the electro-conductivity and temperature of water. The temperature is measured within the sensing cell to provide precision correction. Both temperature corrected and uncorrected conductivity measurements are available for recording.

    A Starlog compatible micrologger is part of the instrument, providing all the standard features such as SDI-12, intelligent battery supervision, modem interface and all the programmability found in Starlog dataloggers.

    Ultra low-power consumption makes the instrument ideal for remote, unattended operation. This instrument will operate for months from a single Model 6910A or 12V battery.

    6536P-2-X probe is designed for use with the 6536E Water Electroconductivity Instrument. It is available in standard cable lengths of 10m and 20m as well as custom lengths up to and beyond 100m.

    Combined with the Starflow 6526H, water flow measurement system, conductivity instrument with probe provides a complete salt load recording package.

    The Dissolved Oxygen Probe is a galvanic measuring element which produces a millivolt output proportional to the oxygen present in the medium it is placed in. It consists of an upper part with 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.

    pH & ORP double junction probes have a rugged design and use a double junction reference system to minimise the effects of contamination due to clogged pores or ingress of sample. They are designed as a low power instrument and include built-in conditioning electronics for direct connection to a Data Logger.

    The Model 6528C 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.

    Model 6528B is an ORP or Redox probe. It measures the Oxidation-Reduction Potential (ORP) of a solution. The ORP value is a measure of the electron activity of a solution containing a reversible chemical reaction system. Typical applications include water treatment and swimming pool or spa water sanitation.

  • Specifications

    EC Operating Range: 0 to 200,000uS/cm in three autoranged stages:

    RangeScale (uS/cm)Resolution (uS/cm)Typical Accuracy
    Low0 to 2000.2+/- 2%
    Mid200 to 20,0002.0+/- 1%
    High20,000 to 200,00020+/- 1%

    Temp Range: -20°C to 60°C
    Temp Accuracy: ±0.1°C
    Temp Resolution: 0.0612°C
    EC Temperature Compensation range: 0–60° C
    Conductivity: 0–200,000 (uncompensated)
    Conductivity: 0–200,000 (temperature compensated)
    Conductivity: 0–65,535 (uncompensated). Low resolution for SDI-12
    Conductivity: 0–65,535 (temperature compensated). Low resolution for SDI-12
    Temperature: -20°C to 60°C
    Battery Voltage: 9 to 12V
    Scan Rate: 5 seconds to 5 minutes (programmable)
    Log Interval: 5 seconds to 1 week (programmable)
    Memory: 512K CMOS
    Power Source: Internal alkaline battery pack with 12 month life expectancy
    External power 9–12V DC can also be connected
    Power Consumption: 0.1Ah per day (at 1 minute scan rate), 55mA operating, 50uA standby
    Size (HxWxL): 75 x 75x 250mm

    Sensor Type: Four Electrode, concentric graphite
    Immersion Depth: 36mm minimum to more than 100m
    Pressure Resistance: 10 bar
    Cell Constant: 0. 475cm-1 ±2.0%
    Thermistor Type: Integrated NTC (30kΩ@25°C)
    Probe Material: Delrin Housing
    Probe Dimensions: 22mm dia x 145mm long
    Cable Length: 10, 20, 30, or 50 meters with 7 pin SQL Plug

    Range: 0-50mV (2.5 to 5mV per ppm mg/l)
    Output impedance: 1kΩ
    Type: Galvanic cell, self polarizing, self temperature-compensating
    Operating Temp.: 0 to 40°C
    Pressure: Submersible to 50m
    Cable: 7m
    Size: 58mm diameter, 59mm long
    Weight: 350g including cable

    6528C and 6528B
    Range pH Probe: 0 to 13pH
    Range ORP Probe: ±2000mV
    Temperature: -5 to 80°C
    Type: Teflon, Double junction
    Cable: 2 wire shielded, 5 metre
    Size: 25mm diameter, 140mm long
    Weight: 50 grams

  • Ordering Information

    6536EWater Electroconductivity Instrument
    6536P-2-10Water Conductivity Probe, 10m cable
    6536P-2-20Water Conductivity Probe, 20m cable
    6536P-2-30Water Conductivity Probe, 30m cable
    6536P-2-50Water Conductivity Probe, 50m cable
    7422ADissolved Oxygen Probe
    6528CDouble Junction, Teflon, pH Probe
    6528BDouble Junction, Teflon, ORP Probe

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  • Documents

    6536E Water Conductivity Instrument

    Unidata Manual – 6536E Water Conductivity Instrument

    Unidata Manual – 7422A Oxyguard Probe

    Unidata Manual – 6528 pH and ORP Sensors

    Application Notes
    Groundwater bore hole monitoring
    Mine site environmental monitoring
    Weather monitoring
    Water quality monitoring

6536E water monitoring conductivity instrument with 6536P-2 probe
6536P-2 Conductivity Probe
oxygen and ph probes