How to Select Manual Pulse Generators
Image credit: Electromate | Euchner USA
Manual pulse generators institute a command pulse when the handle is turned manually.
How Manual Pulse Generators Work
Manual pulse generators are typically rotating knobs that generate electrical pulses. They are normally associated with computer numerically controlled (CNC) machinery or other devices involving positioning. When the pulse generator sends an electrical pulse to an equipment controller, the controller then moves a piece of equipment a predetermined distance with every pulse.
This video details the use of a manual pulse generator (the small black knob at lower left) with a CNC router.
Video credit: urielp911
Manual pulse generators may use one of three different encoder technologies.
Magnetic encoders consist of a plastic drum that turns against a magnetic sensor. The drum is lined with magnetic poles used to generate an electrical signal indicating the drum's position.
Optical encoders use a light source and a photo detector array to read the optical pattern of a plastic or glass disc and translate the pattern into a position data code.
A comparison of a magnetic and optical encoder mechanism. Image credit: Astec Corporation, Ltd.
Mechanical rotary encoders consist of a metal disc with a ring of cut-out openings as well as a row of sliding contacts fixed to a stationary object. The metal disc is attached to a rotating shaft, and each stationary contact is connected to an electrical sensor. As the disc rotates, some of the contacts touch the disc and switch on, while others fall in the gaps where the metal has been cut out. The combination of switched-on and switched-off contacts creates a unique binary code for each disc position.
The GlobalSpec SpecSearch database contains information about a manual pulse generator's count rate, resolution, shaft speed, and diameter.
Count rate refers to the maximum rate of count generation. It is typically expressed in cycles or a variation of Hertz (Hz, kHz, MHz, etc.)
Resolution refers to the number of counts per revolution. In its simplest form, resolution can be determined by the numerical scale markings around the product's knob. Considering that some manual pulse generators are capable of electronic count multiplication and other special features, resolution may be much higher than its marked scale implies.
Maximum mechanical shaft speed refers to the maximum speed at which a pulse generator can rotate without sustaining damage. It is expressed as the number of revolutions per time period (rpm, rps, etc.) or degrees per time period (deg/sec, etc.).
Diameter specifies the body diameter of a circular pulse generator. If the product is square shaped, this spec represents the maximum side dimension as width.
Manual pulse generators may involve analog voltage or digital square wave output formats. Analog voltage is typically expressed as a voltage range, such as 0-10V or ±5V. Square waves are naturally produced by binary devices such as encoders and are therefore a natural choice for pulse generators as well. As shown below, a square wave alternates between regularly between two distinct (binary) levels.
Image credit: Minelab