Water Quality Photometers and Colorimeters

Water quality photometers and colorimeters are ion-specific, computer-interfaced probes that are designed to determine the concentration of a solution from its color intensity. The color of a solution may be inherent, or derived by adding a reagent. Monochromatic light from an LED or other light source passes through a cuvette that contains a solution sample. Some of the incoming light is absorbed by the solution. As a result, light of a lower intensity strikes a photodiode. With water quality photometers and colorimeters, the amount of light that penetrates a solution is known as transmittance, which can be expressed as the ratio of the intensity of the transmitted light to the initial intensity of the light beam.

Water quality photometers and colorimeters produce an output voltage, which varies in a linear way with transmittance. This allows a computer to monitor the transmittance data of a solution, thus producing an output that can be converted to concentration. Electrical output options for include standard voltage and current outputs, as well as an analog pulse or frequency, a change in state of switches, or an alarm. Serial interfaces and parallel interfaces may be used connect water quality photometers and colorimeters to a host computer.

Displays for water quality photometers and colorimeters can be analog meters, a numeric or alphanumeric digital display or video, CRT or LCD. Another option is to have no local display at all and have the data gathered by another instrument. Likewise, the user controls can also be analog or digital, or can be operated through a host computer. To simplify the use of water quality photometers and colorimeters, preprogrammed devices without user controls are available. 

Features for water quality photometers and colorimeters include battery power for greater mobility, auto wavelength selection, and automatic calibration. Temperature compensation is available in some models, as are self-test diagnostic routines to verify sensitivity, zero point, etc. Water resistant housings and data storage and logging capabilities enhance the versatility of water quality photometers and colorimeters.

Mounting options for water quality photometers and colorimeters are varied. Products can be handheld, portable meters or benchtop or fixtured instruments. Handheld meters are popular for laboratory use, where a scientist may be taking readings from many different samples. Portable meters typically have wheels, handles or another device for transportation. Benchtop and fixtured water quality photometers and colorimeters are permanently mounted for long-running use.

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