A colorimeter measures how much light a colored sample absorbs at one fixed wavelength, and for water work that turns a reagent color into a concentration. If your job is testing water, you need a solution colorimeter with built-in calibration curves, such as the OHAUS Aquasearcher AP50, not the surface-color instrument that most "colorimeter" search results describe. This guide separates the two, compares colorimeters with spectrophotometers, and lists what to check before you request a quote.
In this guide
- What does a colorimeter measure in water testing?
- Colorimeter or spectrophotometer: which one do you need?
- What does the OHAUS AP50 colorimeter offer?
- Can a colorimeter also measure turbidity?
- Which vials and accessories do you need?
- How do you choose a colorimeter, step by step?
- Frequently Asked Questions
What Does a Colorimeter Measure in Water Testing?
It measures absorbance: how much of a chosen wavelength of light a reagent-treated water sample absorbs. A test reagent reacts with the target parameter and develops a color, and the instrument converts the absorbance of that color into a concentration using a stored calibration curve. This is the principle behind the colorimetric chlorine test covered in our chlorine meter guide.
The word is also used for a different tool. Surface colorimeters read the color of a solid, such as paint, plastic or fabric, and report color difference values. Those instruments do not test water. ERE lists solution colorimeters in the colorimeters collection, and the rest of this guide refers to those.
Because the method depends on the reagent and the sample, a regulator or a client may name the method they accept. Health Canada's Guidelines for Canadian Drinking Water Quality set the limits; confirm with your lab or authority which analytical method is acceptable for compliance reporting before relying on a field colorimeter for it.
Colorimeter or Spectrophotometer: Which One Do You Need?
Choose a colorimeter for routine, repeatable field or plant checks on a known list of parameters; choose a spectrophotometer when you need to scan wavelengths, develop a method or measure something no preset covers. The practical differences:
| Question | Colorimeter | Spectrophotometer |
|---|---|---|
| Wavelengths | A few fixed wavelengths | A scanned range |
| Calibration | Built-in curves per parameter | Usually you build or load the method |
| Where it works | On site, battery powered | Mostly bench based |
| Best for | Repeat checks of known parameters | Method development, unusual analytes |
A colorimeter is simpler to operate and cheaper to run for a fixed task. Its limit is flexibility: if a parameter has no preset curve and no suitable fixed wavelength, the instrument cannot be extended the way a scanning instrument can.
What Does the OHAUS AP50 Colorimeter Offer?
The OHAUS AP50 Portable Colorimeter is a handheld multiparameter colorimeter with a colorimetric turbidimeter built in. The product record lists the following.
| Item | Record value |
|---|---|
| Preset indicators | Over 50 water quality indicators |
| Fixed wavelengths | 365, 420, 455, 525, 560, 570, 630 nm (7 light sources) |
| Photometric range | 0 to 1 Abs |
| Photometric accuracy | ±0.005 Abs at 1.0 Abs nominal |
| Turbidity optical system | Nephelometric (scattering turbidity method) |
| Display | Backlit graphical LCD, 160 × 240 pixels |
| Power | 4 AA batteries (included); about 6 months typical at 25 readings a week |
| Data storage | 30,000 records with date and time |
| Case | Briefcase |
Two models are listed, A-AP50MM-F and A-AP50MM-B. Their listed specifications are identical, so we confirm the difference and availability on the quote. The record says the instrument selects the wavelength automatically from built-in curves and runs a self-diagnostic during calibration, which reduces setup steps in the field. Which of the 50-plus indicators you can run depends on the reagents you buy, so list your parameters when you ask.
Can a Colorimeter Also Measure Turbidity?
On the AP50, yes: the record describes it as a colorimetric turbidimeter with a nephelometric optical system, which means it measures light scattered by particles. EPA Method 180.1 is the nephelometric turbidity method regulators commonly cite. The AP50 record does not state conformity to that method, so if your program requires it, confirm before ordering. Our turbidimeter selection guide covers dedicated turbidity meters, and the water quality meters guide covers electrode-based multiparameter meters, which measure different things (pH, conductivity, dissolved oxygen) than a colorimeter.
Which Vials and Accessories Do You Need?
Plan vials, a cleaning routine and a cable with the instrument. OHAUS Colorimeter Accessories lists eight part numbers in the record:
- 24 mm replacement vials, 10 mL (pack of 6) and 25 mL (pack of 6)
- A COD adapter listed for the AP50MM
- Replacement vials (pack of 5, 24 mm), cleaning brushes, cloths, a MicroUSB cable and 5 mL cylinders, listed for the related AP30
Scratched or stained vials change absorbance readings, so spare vials and brushes are a consumable, not an extra. Because several items are listed for the AP30, we confirm fit for your model on the quote.
How Do You Choose a Colorimeter, Step by Step?
- Name the parameters. Chlorine, phosphate, iron, COD, turbidity or others; one list drives everything else.
- Confirm the accepted method. Check whether your client or regulator accepts a portable colorimetric method for the parameter.
- Check the range. Keep expected values inside the instrument's 0 to 1 Abs photometric range, diluting if needed.
- Decide field or bench. Battery power and a case favor a portable unit; scanning needs favor a spectrophotometer.
- Plan consumables. Reagents, vials and cleaning supplies are recurring items.
- Set up records. Look at data storage and export if you report to a program.
Need a colorimeter for water testing?
Send us your parameters and sample volume and we will confirm the model, reagents and vials, with delivery across Canada.
Frequently Asked Questions
What is a colorimeter used for?
In water testing, it measures the concentration of a parameter by reading the absorbance of a reagent color at a fixed wavelength. The OHAUS AP50 record lists over 50 preset water quality indicators.
What is the difference between a colorimeter and a spectrophotometer?
A colorimeter uses a few fixed wavelengths and built-in curves; a spectrophotometer scans a range of wavelengths. The AP50 record lists seven fixed wavelengths from 365 to 630 nm.
Can a colorimeter measure turbidity?
The AP50 can: the record lists a nephelometric turbidity optical system. Confirm method acceptance if your program requires a named method.
How long do the batteries last?
The record gives about 6 months typical at 25 readings a week, on 4 AA batteries that are included.
Do you quote colorimeters for delivery across Canada?
Yes. Send your parameters through the quote form and we confirm model, accessories and availability.
Related articles
- Chlorine Meter Buyer's Guide for Canada
- Turbidimeter Selection Guide for Environmental Monitoring in Canada
- Water Quality Meters for Environmental Work
Lire en français : Colorimètre : guide pour l'analyse de l'eau et comparaison avec le spectrophotomètre au Canada