The STH-manufactured Brinkmann PC 950 Probe Colorimeter, a lab favorite for measuring the optical transmittance, absorbance, and/or concentration of liquids, is easy and convenient to use. Designed for use in the visible/near infrared photometric range, it features a precisely controlled light source (lamp), fiber optic probe, interface filter(s), and photodiode measurement cell to determine the amount of light that passes through a liquid.

Easy to use with precise results
Extraneous ambient light does not affect measurements, and readings can be taken at any level of illumination - artificial or natural. Simply insert the fiber optic probe tip directly into your sample container - from 0.5 ml test tubes to large vats and pipelines - and read/print the results. By measuring samples in their own container, errors from temperature or turbidity changes are substantially reduced - and no cuvettes means no breakage or cleaning problems.


  • For use in pharmaceutical, water, and wastewater analysis
  • For food and beverage quantitative and qualitative analysis
  • pH and redox measurements and titrations for Ce, Cr, Cu, and Fe
  • Complexometric titrations for Ba, Pb, Mg, and total hardness
  • Turbidimetric titrations
Filter wavelengths for applications:
Ammonia 450 nm - 500 nm
Chloride 470 nm
Chlorine 520 nm
Chromium 545 nm
Copper 470 nm
Cloud point 40% Neutral density
Cyanide 570 nm
Nitrate 420 nm
Phenol 500 nm
Silica 660 nm - 700 nm
Sulfate 520 nm
Phosphorus 420 nm - 470 nm or 880 nm


  • Read absorbance, transmittance or concentration
  • Select from filters ranging from 420 to 950 nm
  • Analog output—for connection to titrator or chart recorder
  • Serial port - for connection to a printer or PC

Using the PC 950 Probe Colorimeter

This instrument is the latest embodiment of 40 years experience with the probe colorimeter, the simplest and most convenient colorimeter you will ever use to read transmittance, absorbance, and concentration. Select an appropriate filter (420-950 nm), insert the probe directly into the test solution, and read the result.

The basic system uses a tungsten filament pulsed light source to provide light going to the solution through fiber optics; this light is reflected back by a mirror built into the probe and returned to the instrument where it passes through the selected filter and impinges a photodiode. This reading is compared to a calibrated 100% transmittance reading.

Test samples can vary from small test tubes to large vats or flow through a pipe (using swagelok® fittings.). Sensitivity is doubled because of the optical path through the fluid - a 1 cm light path probe has actually a 0.5 cm opening. Readings are unaffected by ambient light, and a reference diode is used to compensate for lamp aging to improve long term stability. A selectable measurement time is a standard feature. Depending on your application, the instrument can be customized as a variety of fiber optic lengths (up to 10 meters), probes of various materials (stainless steel, Pyrex®, polycarbonate), and special filters are available.
Display resolution Transmittance 0.1%
Absorbance 0.001 units
Two analog outputs 0 V to 1 VDC
4 mA to 20 mA
RS-232 output 25-pin
Power input 0.5 A, 12 VDC (transformer provided)
Display Six digit alphanumeric LED
Dimensions 20.3 X 14 X 6.3 cm
Weight 1.5 kg

Pyrex® is a registered trademark of Corning Glass Works. Swagelok® is a registered trademark of Crawford Fitting Company.

CE marking compliant

Linearity, Beer’s Law, and the PC 950
Linearity is an extremely important factor, especially when using light as an analytical tool. When measuring according to Beer’s Law, there should be minimal errors when comparing and plotting absorbance (A) versus concentration.

The PC 950 Probe Colorimeter shows excellent linearity in measurements from A = 0 to 1.4. This ensures that any changes in the measured values are from the sample and not the instrument.
Beers Law
Click image for a larger size

PC 950 and Metrohm® Titrators for more advanced analysis

The PC 950 Probe Colorimeter can be combined with any automatic titrator, but when combined with Metrohm titrators it forms the perfect system for fool-proof measurements. Connected by analog signal, the PC 950 provides measurements for colorimetric and turbidimetric titration.

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