Water Quality Instruments and Probes

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), dissolved oxygen (DO). Unidata range of water quality monitoring instruments and probes consists of:

The 6536 Water Conductivity Instrument with 6536 Probe measures the electro-conductivity and temperature of water in streams, rivers, lakes and the groundwater system, using boreholes. The temperature is measured within the sensing cell to provide a precision correction. Both, temperature corrected and uncorrected, and conductivity measurements are available for recording.

A Starlog compatible micrologger with 512KB memory is part of the instrument, providing all the standard Unidata data logger features such as SDI-12, intelligent battery supervision and modem interface. Ultra-low power consumption makes the 6536 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 6526J, water flow measurement system, conductivity instrument with probe provides a complete salt load recording package.

pH double junction probe 6528 have 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 which 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.