Principle of Operation - Rotary Motion Sensor

How do the PASCO rotary motion sensors (RMS) work? Though there are several models of rotary motion sensor, they operate on common principles described in the article.

 Related Products: 

  • PS-3220 Wireless Motion Sensor
  • PS-2120A PASPORT Motion Sensor
  • CI-6538 Rotary Motion Sensor (ScienceWorkshop)


PASCO Principle of Operation:

PASCO Rotary Motion Sensors consist of a 3-step pulley mounted on dual ball bearings. Rotating the shaft turns a nylon gear with an interrupter through an internal photogate. The output from the sensor consists of two trains of TTL digital pulses that represent movement in each direction.  The digital encoding of the signal occurs on board the sensor for the PS-2120A PASPORT Rotary Motion Sensor and the PS-3220 Wireless Rotary Motion Sensor.  Digitization of the data from the CI-6537 ScienceWorkshop Rotary Motion Sensor occurs within the interface to which the sensor is connected.

CI-6538 Specific Technical Details

The electrical connections are as follows:

Yellow Cable

  • sleeve: GND
  • ring: + CNT
  • tip: + 5 V

Black Cable

  • sleeve (black): GND
  • ring: - CNT
  • tip: NC

Both rings should pulse low for one clock cycle in order to change from 360 to 1440 counts per revolution.

Date Created: 01/02/2020
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