How does an encoder work?！

• Reluctance Style (Tachometer)

  A magnetic pickup is used to sense the magnetic poles on a steel rotor (gear). By varying the number of teeth on the rotor, the number of pulses per revolution (PPR) will vary.

  The output of a reluctance style tachometer is a sine wave. Reluctance tachometers do not require a power supply, so their base cost is low. However, the unamplified sine wave signal is not as strong as "zero-speed" or "square wave" style encoders. Also reluctance tachometers do not sense speed at low RPM. Typically, their output does not reach an acceptable level until the speed reaches 30-50 rpm.

  Sine wave tachometer signals usually operate above and below zero volts during any one pulse cycle. Sine wave output values are usually expressed as voltages "peak to peak", or in other words, a measurement from the maximum above zero value to the minimum below zero value. Contact Roundss to replace obsolete reluctance style tachometers.

• Magnetoresistive

  These sensors use resistors that are sensitive to magnetic fields. When a rotor with magnetic poles is sensed, a sine wave is generated which is then converted to a square wave. This pick-up is more sensitive and thus can operate from 2 to 8192 PPR depending on the model being used. They require a power supply which permits operation down to zero speed and can drive cable lengths up to 2000 feet! Roundss Wide-Gap magnetoresistive technology resists interference from motors and brakes,and eliminates sensor scraping damage.

• Photoelectric/optical

  This system uses an infrared LED light source that shines through a rotating, slotted or photo-etched disk, and on to a photoelectric cell. When the slots align with the LED, light shines through to give a high output from the sensor. When they misalign, the output goes low. The signal generated is amplified and produces a square wave output. This design allows up to 32768 PPR and operation down to zero speed (see models for details). They require an external or drive power supply. Roundss Wide-Gap optical technology eliminates sensor damage from shock or vibration and Roundss never uses fragile glass disks.

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