How do Chlorine Meters work?
Chlorine measurement uses either a colorimetric or an electrochemical principle. In the DPD method, N,N-diethyl-p-phenylenediamine reacts with free chlorine to form a magenta colour whose intensity is proportional to concentration and is measured at about 515 nm; adding potassium iodide then reveals combined chlorine so total chlorine can be determined. Because the colour develops quickly and fades, timing and temperature must be controlled. Amperometric analyzers use a membrane-covered electrode where chlorine diffuses to a cathode and produces a current proportional to concentration, giving continuous measurement without reagents. Optical analyzers use a colorimetric reaction in a flow cell with automatic reagent addition. Results are reported in milligrams per litre as free chlorine, combined chlorine, total chlorine or, in pools, as total chlorine with cyanuric acid present.
Which Chlorine Meters variants are available?
- Portable DPD Chlorine Colorimeter — A portable DPD chlorine colorimeter measures free, combined and total chlorine in the field using tablet or powder reagents and a photometer.
- Benchtop Chlorine Colorimeter — A benchtop chlorine colorimeter measures free, combined and total chlorine with stable optics and controlled wavelength selection.
- Online Amperometric Residual Chlorine Analyzer — An online amperometric chlorine analyzer measures residual chlorine continuously with a membrane-covered electrode.
- Pocket Chlorine Tester for Field Use — A pocket chlorine tester is a compact, low-cost photometer for single readings of free or total chlorine.
- Optical Chlorine Analyzer for Drinking Water Plants — An optical chlorine analyzer performs a colorimetric reaction in a flow cell with automatic reagent dosing to measure residual chlorine continuously.
How do I choose the right variant?
Choose the measurement format from where and how often chlorine is measured. Pocket testers and portable colorimeters suit field checks, pool testing and distribution system sampling, where speed and portability matter. Benchtop colorimeters give better optics and repeatability for laboratories and for verifying portable meters. Online amperometric analyzers are needed wherever chlorine dosing must be continuous, as at treatment works, since they respond in seconds and can drive pumps and alarms directly. Consider the expected range, since disinfection residuals are usually 0.2 to 2 mg/L but pool and shock dosing levels are far higher, and confirm whether free, combined or total chlorine is the reported parameter. Check reagent or membrane availability and the calibration standards you will need.
Where are Chlorine Meters used?
Chlorine Meters are specified in drinking water disinfection monitoring, swimming pool and spa water testing, wastewater effluent chlorination control, food and beverage plant water hygiene, cooling water and industrial process control and distribution network residual chlorine surveys.
Which standards and certifications apply?
Work with Chlorine Meters is commonly governed by ISO 7393-1, ISO 7393-2, ISO 7393-3, EPA 330.5, Standard Methods 4500-Cl G and ISO/IEC 17025. Instrument certifications such as CE marking are confirmed per configuration and never assumed.
What are the key considerations before purchase?
DPD reagents and powder pillows have a limited shelf life and are sensitive to heat and moisture, so they must be stored correctly and replaced before expiry. Colour development depends on time and temperature, so sample temperature should be near 20 to 25 °C and readings taken within the specified period. High chlorine concentrations bleach the colour and need dilution, and samples with manganese, ozone or high turbidity can interfere. Membrane electrodes need electrolyte replacement, membrane care and regular calibration against a reference method, and the sample flow, pH and temperature must be within the specified limits. For pools, cyanuric acid affects the ratio of free to combined chlorine and should be known. Keep records of calibration, reagents and reference comparisons.
