Model 197 precision Light Choppers

Ideal for use in modern photometic systems


The model 197 is a compact, high performance chopper, offering features and benefits that are ideal for use in modern photometic systems.

Supplier: Signal Recovery


  • Without external controller
  • Double opening
  • Internal and external opening
  • Synchronization outputs

The unit is self contained, comprising a dual aperture chopper blade, motor and the necessary driving electronics. Each aperture provides an independent reference output allowing simultaneous dual frequency operation (10:1 ratio) for dual-path experiments. Frequency control is by a precision internal oscillator set by a 4-digit push-button selector on the unit or by the application of an external AC reference signal. The unit is powered via an external line power supply module.


  • Modulation 1: 150Hz to 3000Hz
  • Modulation 2: 15Hz to 300Hz
  • Accuracy ± 20 ppm at 25 ºC
  • Manual or external control (0.5V to 10V sinuzoidal or peak to peak)
  • 10V peak-to-peak sync paths

Product applications

  • Absorption, reflection and optical transmission
  • Dual radiometric measurement