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Catalogue A25S Absolute Rotary Encoder

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SPECIFICATIONS

ACHIEVING ACCURACY

These design features assure the high accuracy and long-term stability of the Model A25S:

• Multiple reading heads are used in the transducer to eliminate errors caused by disc eccentricity, pattern irregularities and non-uniform bearing rotation.

• Back-to-back photodiodes "read" the interpolated track in push-pull configuration to eliminate errors caused by LED aging, temperature changes, supply voltage variations and other common-mode effects.

• Interpolation is accomplished with proprietary high-speed phase-angle conversion circuitry, which produces true position data very quickly and very accurately. The circuitry has been designed for reliable and predictable performance over the rated temperature environment.

• Because output data is made available only when the user provides an interrogate pulse, there is no possibility of "chatter" in the vicinity of a data transition, and hence no need for hysteresis in the circuitry. This unique zero-hysteresis feature assures error-free operation in bi-directional applications.

ABSOLUTE POSITION ENCODING

The Model A25S is a high performance absolute optical encoder designed for resolution in the 2¹⁴-2¹⁷ range. Its position information is stored in a non-volatile fashion in the multi-track absolute code pattern on the disc. If power is lost and re-applied, absolute position data is immediately available without "homing" the encoder or counting pulses, as is typically required with an incremental device. It is especially well-suited for applications requiring the highest possible data integrity where electrical noise, safety or high performance are important system considerations.

ROBUST MECHANICAL DESIGN

The A25S consists of a low-profile transducer module and separate electronics package - a configuration that allows it to be used where conventional designs will not fit. The rugged 3/8" dia shaft/bearing assembly assures long life in a variety of industrial applications. A proprietary electronic circuit permits the use of a lower resolution code disc; this minimizes sensitivity to optomechanical adjustments and thus maximizes long-term mechanical stability.

REMOTE ELECTRONICS

The separate electronics is housed in a compact 4.2" x 2.8" x 0.9" enclosure that can be located up to 25 ft from the transducer (standard cable length is 4 ft).

MECHANICAL


	Maximum weights
	Steel transducer, 48" cable*	19 oz (540 g)
	Aluminum Transducer 48" cable** 13 oz (370 g)
	External electronics	5 oz (140 g)
	Jacketed cable	0.118 oz/in (132 g/m)
	Moment of inertia	9.0 x 10^-4 in-oz-s² (63.2 g-cm²)
	Starting torque	2.0 in-oz (14.0 x 10^-3 N-m)
	Running torque	1.0 in-oz (7.0 x 10^-3 N-m)
	Max. recommended shaft load
	Axial	13 lb (58 N)
	Radial	10 lb (45 N)
	Bearings	Sealed ABEC 7
	Code disc	chrome on glass
	Max. operating speed	600 rpm
	Max. slew speed	10,000 rpm
	* TEMP = A or T
	** TEMP = C
	ENVIRONMENTAL
	Operating temperature
	Commercial	32^oF to +158^oF (0^oC to +70^oC)
	Automotive	-40^oF to +185^oF (-40^oC to +85^oC)
	Storage temperature	-40^oF to +194^oF (-40^oC to +90^oC)
	Humidity	98% rh, non-condensing
	Altitude	0-50,000 ft, (0 - 15.24 km)
	Shock	50 g, 11ms
	Vibration	15 g, 0-2000 Hz
	Transducer	IP40
	Electronics	Ip60
	ELECTRICAL
	Input power	+5 Vdc ±0.25 Vdc, 300 mA max
		(excluding output buffer requirements)
	Illumination	Light-emitting diodes, screened and rated
		for 100,00-hr life
	Max resolution	2¹⁷ (131,072) unique words per shaft
		revolution (other resolutions available; see
		Ordering Info.)
	Accuracy	Each data transition is within ±15 arcsec
		of its true position, regardless of resolution.
		The error distribution is such that each
		output code state is always present and in
		the correct order.
	Output code	Natural binary (consult factory for other
		codes)
	Output format	Parallel or serial
	Direction of increasing count	User selectable (factory default = cw)
	Parity	User selectable (factory default = odd)
	Parallel Output	TTL-compatible tri-state buffered registers.
		Byte-wide or word-wide (user selectable)
		format.
	Input device	Schmitt trigger input for interrogate pulse.
		TTL compatible output enable line(s).
	Max data update rate	1 MHz
	Serial output	Synchronous output with EIA/RS-422
		differential line drivers. MSB first; parity last
	Input device	EIA/RS-422 differential line receivers for
	Input device	interrogate pulse and clock input.
	Max data update rate	100 kHz@3.6 Mbaud

The encoder is designed so that it may be connected directly to the data bus of a microprocessor or microcomputer. It offers the advantages of high accuracy, simplified hardware and software interfacing, robust opto-mechanical design, wide operating temperature range and very fast response time.

The Model A25S is ideal for any motion control application requiring an absolute encoder with high resolution, accuracy and reliability in a compact configuration. Typical applications include robotics, precision servo controls, radar pedestals and similar AZ-EL mounts, rotary tables and machine tools.

NOTE: These specifications are applicable under all variations of recommended supply voltage, speed, temperature and direction of travel. Improved performance is available under special conditions; please consult factory.

Gurley Precision Instruments 514 Fulton Street Troy, NY 12180 U.S.A. (800) 759-1844, (518) 272-6300, fax (518) 274-0336, Online at www.gurley.com, e-mail: info@gurley.com

A25S

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