Monitor for measuring important water quality parameters

Analytical Instrumentation & Environmental Monitoring

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February 2007 Analytical Instrumentation & Environmental Monitoring

Horiba's U-10 Water Quality Monitor measures six parameters, namely pH, conductivity, turbidity, dissolved oxygen (DO), temperature and salinity. What used to be a complicated calibration process is now easy. The supplied beaker is filled with the standard solution, the sensor immersed, and the user simply presses a button, once for one-point calibration for each of the four parameters pH, conductivity, turbidity and DO. Two-point calibration is also possible should more precise data be required.

The instrument stores the measurement results of all six parameters for up to 20 samples. There is no need to record measured values on site. Data stored in memory can be recalled and displayed at any time, and can even be simultaneously printed out on any standard printer by connecting it to the Centronics-specification printer output terminals.

It is now possible to measure DO in either fresh or salt water with the same instrument. When measuring DO in salt water, it will automatically measure the salt concentration and make the salinity correction. It is also possible to set a freely selectable salinity correction factor of between 0 and 4%. If more precise data is required, the user simply selects the expanded display mode to display data on any parameter to one more digit of resolution.

The U-10 sensor operates by being directly submersed in the river, sea or other water, eliminating troublesome sampling. The standard cable length is 2 m, but the sensor is constructed to be able to withstand water pressure at depths of up to 10 m and is thus suitable for an even wider range of applications if used with the optional 10 m cable.

A data back-up function ensures that precious data is never lost by accident. Sensor calibration values and stored data remain safely in the memory even if the batteries run down. Attention to the small details has resulted in an automatic energy-saving function that switches the instrument off automatically any time 30 minutes pass without any key being pressed. The glass electrode and reference electrode are of the cartridge type so they are simple to replace and require no maintenance.

Alternating the four-electrode cell makes the instrument resistant to the effect of polarisation, providing reliable, stable data even at high concentrations. The range switches automatically to the most appropriate of three 0-1 mS/cm, 1-10 mS/cm, or 10-100 mS/cm depending on the sample.

The light source is an LED. This method gives a broader measurement range than optical systems based purely on transmitted light or scattered light and is little affected by particle coloration, thus giving highly dependable data. The membrane/galvanic cell is capable of stable data display, unaffected by coexisting gases other than oxygen. The thermistor can measure from 0 to 50°C and it can also be used for automatic temperature compensation when measuring pH, DO and conductivity.

Horiba is represented locally by OEN Enterprises.

For more information contact Mike Andrews, OEN Enterprises, +27 (0) 11 675 4447, mike@oenenterprises.co.za or visit www.oenenterprises.co.za

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Analytical Instrumentation & Environmental Monitoring

Monitor for measuring important water quality parameters

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