Heavy Duty Encoder - Hengstler Encoders

Technology overviewIncRementAl encodeR oveRvIewIncremental encoders provide a specifiedamount of pulses in one rotation of the encoder.The output can be a single line of pulses(an“A” channel) or two lines of pulses(an “A” and“B” channel) that are offset in order to determinerotation. This phasing between the twosignals is called quadrature.The typical assembly of incremental encodersA-A*is reduced to a spindle assembly, PCB, andcover. Each component bears a similar purpose as the in the absoluteencoders with the exception that the PCB contains a sensor arraythat creates just two primary signals for the purpose of position andB-B*speed.Optionally, additional signals can be provided:An index or ‘Z’ channel can be provided as one pulse per revolutionsignal for homing and pulse count verification on the A and/or B channels.This index can be gated to either A or B in their various states. Itcan also be un-gated and vary in width.Commutation(U,V,W) channels can also be provided on some encoders.These signals are aligned to the commutation windings found onservo motors. They also ensure that the drive or amplifier for thosemotors apply current to each winding in the correct sequence and atthe correct level.ResolveR oveRvIewA resolver functions as an electro-mechanicalposition transducer which is essentially a variablecouplingor rotary transformer.Like all transformers, the resolver requires an ACcarrier or reference signal (input excitation) to beapplied to the primary winding, contained in therotor. The resulting changing magnetic field in theprimary winding induces a voltage in the secondarystator windings.The secondary of the resolver stator consists oftwo sets of windings that are at right angles to each other.The magnitude of the magnetic coupling between the primary andthe secondary varies according to the position of the rotating element(rotor) which then varies the amplitude of the output voltage. The amplitudeof the reference or input signal is modulated by the sine andthe cosine of the rotor angle to produce the sine and cosine outputsignals on the two secondary windings as shown in Figure 7.Typically, there is one sine and one cosine wave per mechanicalrevolution which provides absolute position. A multi-speed resolvercreates multiple sine and cosine waves throughout a revolution, whichincreases accuracy but at the expense of absolute position.ABZFigure 6: Incremental O° Encoder Signal 360°/2048180°eCH. A90°eCH. B180°eCH. Z±1°mCCW Shaft Rotation180°eCH. U120°eCH. V120°eCH. WFigure 7: Commutation ChannelsFigure 7: Resolver SignalA.06