Spectrophotometers measure light’s wavelength distribution by providing the percentage of reflectance from an object, detecting the color of the sample. There are two types of beam spectrophotometers — single beam spectrophotometers and double beam spectrophotometers. These instruments have several key differences you should keep in mind when deciding which is best for your laboratory.

Single Beam Spectrophotometer

Single beam spectrophotometers determine color by measuring the intensity of the light sources before versus after a test sample is inserted. This light source is modulated (turned on and off) to differentiate the light coming from the light source versus the light coming from the flame.

The single light beam passes through the sample, and the single beam spectrophotometer measures the intensity of the light reflected from the reference to measure the sample.

Double Beam Spectrophotometer

Double beam spectrophotometers measure color in a sample by using two, or “double,” beams. One beam passes through the sample side, and the other beam passes through the reference side, so the reference and the sample can be read simultaneously with no need to recalibrate the instrument.

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The double beam spectrophotometer measures absorbance versus wavelength, or the ratio of the sample and reference beams. These beams are recombined before they go to the monochromator to mitigate mechanical fluctuations, lamp intensity and other effects.

Choosing Which Spectrophotometer Is Best

There are many advantages of single and double beam spectrophotometers, but there are some applications where one instrument is the best choice.

The benefits of single beam spectrophotometers are:

  • Better performance: Since the beam is not split, there is a high energy throughput. This throughput makes the detection highly sensitive.
  • Lower cost: Single beam spectrophotometers are more cost-effective than other options.
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If your application calls for stability, the single-beam spectrophotometer may not be the best option because this instrument does not compensate for disturbances like voltage fluctuations that influence the results.

The benefits of double-beam spectrophotometers are:

  • Reliable detection: The automation and improved optics lend to the highest level of detection possible. It mitigates disturbances so they don’t affect the measurements.
  • No warmup time: The lamp does not need to warm up, conserving lamp life and improving the throughput of results.

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For more than 65 years, HunterLab has used scientific tools and methods to determine color and appearance as accurately as possible. You can trust that our measurements are right every time.

Contact HunterLab online today for more information about our color measurement instruments and services. Check out our blog to read more posts about measuring color.