The PC-QD is a quadrature meter that accepts the A & B quadrature signals from linear encoders or shaft encoders to provide a highly accurate, scaled display of position, length, or angle in engineering units, such as ft, cm or degrees. The A & B quadrature signals are 90° out of phase, and their phase relationship determines whether up counts (+) or down counts (-) are counted. The PC-QD meter totalizes the counts and then scales the total for display and control. A zero index signal, or Z signal, may be added as a third input to the A & B signals.
Use of the optional extended counter can convert the quadrature meter from scaled position to scaled rate. For example, it can display the speed of a moving slab in ft/sec. Simultaneous display of position and rate will require two meters. The display and control output update rate for position or rate is normally set to a maximum of 25/s, as determined by a user programmable gate time.
The PC-QD can count one, two or four transitions at a maximum combined rate of 250 kHz and be mathematically scaled for display in engineering units from -999,999 to +999,999. The quadrature board has input circuitry which may be jumpered for either single-ended input signals or for balanced line driver signals. Anti-jitter circuitry eliminates errors produced by vibration of the encoder. In the event of a power failure, the latest total may be stored in non-volatile memory and can be used as the starting point for counting when power resumes. Power fail save or zero index capabilities are selections available in the menu programming.
If provided by the encoder, a zero index pulse is interpreted by the meter as indicating a zero reference for an integral number of revolutions of a rotary shaft encoder or the home position of a linear encoder. It is used by the meter for initializing and to correct for any cumulative pulse count errors. Special circuitry corrects for width of the zero index pulse.
The PC-QD’s offer Universal AC or DC power selections which enables flexibility with usage in various power situations. Optional 8 A contact or 120 mA solid state relay outputs, plus an analog process signal output with 4 user-selectable current or voltage ranges are available. To provide a higher level of communication and integration into a system’s network, several communication protocols such as RS-232, RS-485 and even USB options are available. Units come standard with an isolated excitation output to power transducers, eliminating need for additional power supply.
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