Precision Light Chopper

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

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.

Mounting holes are provided in the base and right-hand side of the housing (viewed from the front) to allow for mounting the model 197 onto an optical bench or support post.


  • Self contained chopper head
  • Quartz crystal frequency accuracy and stability
  • Internal or external frequency reference
  • Sync outputs
  • Fully enclosed housings for safety and low noise
  • Optical absorption, reflection and transmission measurements
  • Dual-beam ratiometric measurements
  • Automatic background subtraction in boxcar averager experiments



This product could be used for the following applications:

  • Optical absorption, reflection and transmission measurements
  • Dual-beam ratiometric measurements
  • Automatic background subtraction in boxcar averager experiments


This product is manufactured by SIGNAL RECOVERY.

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