Water professionals often use the word colorimeter for very different instruments. A portable or laboratory colorimeter is designed for an operator to test a sample. An online colorimetric analyser is installed at the process and performs a defined wet-chemistry method automatically. Understanding that distinction helps you choose the right approach.
What does a water colorimeter measure?
Colorimetry measures the intensity of colour produced by a chemical reaction. A reagent reacts with the target substance and creates a coloured compound. The instrument measures light absorbance and relates that result to concentration through the selected analytical method.
The chemistry is parameter-specific. Reagents, wavelengths, reaction times, measuring ranges and possible interferences differ between methods. This is why an instrument should be selected around the parameter, expected concentration and sample conditions, not simply because it is described as a colorimeter.
Portable and laboratory colorimeters
A portable or benchtop colorimeter is typically used for a test carried out by an operator. The user collects a representative sample, prepares it, adds the specified reagents, waits for the reaction and records the result. These instruments are useful for spot checks, laboratory work, commissioning, troubleshooting and measurements taken at multiple locations.
- Suited to manual spot checks and occasional measurements
- Can be moved between sampling points
- Requires consistent sampling, preparation, timing and record keeping
- May be the most practical option when measurements are infrequent
- Supports laboratory or field procedures defined by the selected method
The quality of a manual result depends on the complete procedure. Sample collection, clean glassware, reagent handling, reaction timing, calibration and operator technique all matter.
Online colorimetric analysers
An online colorimetric analyser is installed close to the process and repeats a programmed analytical sequence. It draws a sample, adds reagents, performs the reaction, measures the colour and reports the result. This makes it possible to obtain routine measurements without an operator performing every test.
- Suited to repeated measurement at defined sampling points
- Provides results between manual or laboratory checks
- Can support process trending and treatment decisions
- Requires a representative sample and suitable sample conditioning
- Needs reagent, calibration, cleaning and maintenance planning
Online analysis does not automatically make every water stream suitable. Colour, suspended solids, temperature, pH, interfering chemicals and the expected concentration range must be considered. Filtration, cooling, pressure control or other sample preparation may be required.
How the 3S online colorimetric analyser works
The 3S-CL is a configurable online wet-chemistry platform. It is supplied around a selected analytical method rather than as one universal instrument for every parameter. The analyser manages the sequence of sampling, reagent addition, reaction, optical measurement, calculation and cleaning for the approved configuration.
Automatic routines can reduce variation in timing and handling between tests. The analyser can also support automatic calibration, validation and cleaning when these routines are configured for the application. Read the guide to automatic calibration, validation and cleaning for the practical distinction between those functions.
The available chemistry is broad, but each application remains method-specific. Review the online water analyser parameter range and confirm the current method documentation before specification.
Portable colorimeter or online analyser: which should you choose?
Choose a portable or laboratory colorimeter when:
- You need occasional measurements rather than a continuous routine
- One instrument must serve several changing sampling locations
- An operator or laboratory already performs a controlled manual method
- The sample requires preparation that is difficult to automate
- You need an independent check alongside an online instrument
Consider an online colorimetric analyser when:
- You need repeatable measurements at regular intervals
- Process conditions can change between manual tests
- Operators need trends to support treatment decisions
- The sampling point can provide a representative, conditioned sample
- The analytical method, range and matrix have been reviewed for online use
Many sites use both approaches. An online analyser provides routine operational information, while portable or laboratory tests support checks, investigations and required analytical programmes. Accredited laboratory analysis and statutory sampling remain necessary wherever the application requires them.
Questions to answer before selecting an online colorimeter for water
- Which parameter is required? The analytical chemistry must match the substance being measured.
- What concentration range is expected? Include normal, low and high conditions.
- Where will the sample come from? The sampling point must represent the process condition you want to understand.
- What is in the sample matrix? Consider colour, solids, temperature, pH and possible chemical interferences.
- How often is a result needed? Analysis time and frequency affect reagent use and maintenance planning.
- What will the result be used for? Process control, trend monitoring and compliance programmes can have different requirements.
- What sample conditioning is needed? Challenging samples may require filtration or other preparation.
- How will performance be checked? Define calibration, validation, cleaning and comparison with laboratory results.
Common questions
Is an online colorimetric analyser the same as a portable colorimeter?
No. Both can use colorimetric chemistry, but a portable or laboratory colorimeter relies on an operator to prepare and test the sample. An online analyser performs a defined sequence automatically at an installed sampling point.
Can one online analyser measure every water parameter?
No. The analyser must be configured around compatible parameter-specific chemistry. Measuring range, reagents, analysis time and possible interferences depend on the selected method.
Does an online analyser replace laboratory testing?
No. It can provide frequent operational information between manual or laboratory checks, but it does not replace accredited analysis, statutory sampling or application-specific compliance instruments where those are required.
What information does PMA need to review an application?
Provide the parameter, expected concentration range, sample source, sample condition, required analysis frequency, installation environment and intended use of the result. PMA can then review the suitable 3S method and sample-conditioning approach.
Discuss your water-analysis requirement
Explore the 3S application areas, then contact PMA with your parameter, expected range and sample conditions for a technical review.