Water Quality Instruments and Probes

Water Quality Instruments and Probes

Model 6536F, 6537A, 6528C and 7422A

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 four-electrode sensor 6536F uses an alternating current of constant voltage established between a primary pair of graphite electrodes. The secondary platinum electrodes regulate the voltage imposed on the primary electrodes to reflect the fouling. The voltage measured between the primary electrodes is a function of the resistance between them and, consequently, the conductivity of the solution.

Overview

The sensor features excellent interference immunity thanks to the integrated preamplifier and digital signal processing. The measured value for conductivity is automatically compensated with the temperature and transferred without interference to the connected display unit and controller via a digital interface.

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.

Specifications

pH and Dissolved Oxygen Probes

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

6537 Starflow QSD

7422 Dissolved Oxygen Probe

Ordering Information
Model
Description
6536F
Conductivity Digital Sensor
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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