Delta MMC120 User Manual download pdf (Page 13)

MMC120 Linear Motion Control Module Description

Delta Computer Systems, Inc. 360/254-8688 13

DESCRIPTION

Principle Of Operation

Position Measurement

The MMC120 has interface circuitry for two magnetostrictive transducers. Each axis can be configured for a

Start/Stop transducer or a Pulse Width Modulated transducer by changing the axis' Configuration Word. To

make a measurement with a Start/Stop transducer, the MMC120 sends an interrogation pulse to the

transducer. The transducer responds by returning 2 pulses -- a 'Start' pulse and a 'Stop' pulse. The counters

on the MMC120 are active between the two pulses. The time between the pulses is proportional to the

transducer position.

Interrogation

Pulse

Start Pulse

Stop Pulse

Counters Active

Start/Stop Pulse Transducer

To make a measurement with a Pulse Width Modulated transducer, the MMC120 sends an interrogation pulse

to the transducer. The transducer responds with a return signal that is high while the transducer is

determining its position. The counters on the MMC120 are active while the return signal is high. The width

of the return signal is proportional to the transducer position.

Interrogation

Pulse

Counters Active

Return Signal

Pulse Width Modulated Transducer

While the counters on the MMC120 are active, they count the number of half-cycles of a 60 MHz clock (120

MHz effective rate). At this frequency, each half-cycle represents less than 0.001 inch displacement of the

axis.

The MMC120 converts the Transducer Counts read from the counters to an ACTUAL POSITION in user-

defined Position Units (usually 0.001 inch) for use by the Quantum Programmable Controller.

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Delta MMC120 User Manual Page 13