ingenuity@work - Gurley Precision Instruments
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1. Once the first tag has been obtained from the disc bit wise during the initialization traverse ensuing motions modify the tag based on direction of motion Direction sense is always available from the quadrature incremental track waveforms As new tags become available they are decoded into monotonic natural binary absolute position words During the tag decoding process an exor gate compares each new detected bit obtained from the index track against the bit the tag decoder predicts for that direction of motion In effect the decoder knows the entire serial code sequence and reports any disagreement between expected and detected tag bits as a fault condition In this way the encoder s design embodies a sophisticated real time automatic error detection technique that is constantly on guard against malfunction with every motion of the disc This capability is equivalent to the most fully refined monotonicity test system possible in a conventional absolute encoder yet imposes no appreciable overhead in hardware because it is a natural byproduct of GPI s patented tag decoding method AGPI Virtual Absolute encoder system can be in any one of 3 distinct operating modes e Wait mode It may be aware of an interruption of power or some other interference to normal operation which it interpreted as an invalid tag Until a re initialization traverse has been executed to refresh the code tag in the decoder the VA reports a fault condition while it is wait2. higher frequency response greater accuracy wider temperature range reduced torque non standard line counts or other modified characteristics In addition we regularly design and manufacture custom encoders for user specific requirements These range from high volume low cost limited performance commercial applications to encoders for military aerospace and similar high performance high reliability conditions We would welcome the opportunity to help you with your encoder needs WARRANTY Gurley Precision Instruments offers a limited warranty against defects in material and workmanship for a period of one year from the date of shipment VS60H PAGE 8 oF 8 V3 1 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
3. operating speed 120 s Operating temperature F C 40 to 185 40 to 85 Storage temperature F C 58 to 212 50 to 100 Humidty 98 rh non condensing Weight encoder coupling Ib kg 12 Ib 5 5 Starting torque in oz N m 16 0 11 Running torque in oz N m 12 0 08 Moment of inertia in oz s g cm 0 27 19 x 10 Sealing IP64 Custom resolutions available up to 24 bits Please contact factory for more information At 20 C As part of our continuing product improvement program all specifications are subject to change without notice Gurley Precision Instruments VU S 6 U H 514 Fulton Street Troy NY 12180 U S A PAGE 2 OF 8 800 759 1844 518 272 6300 fax 518 274 0336 v3 1 Online at www gurley com e mail info gurley com THEORY OF OPERATION A Gurley Virtual Absolute VA encoder employs an optical encoding technique which is still relatively new to the motion control industry Like an incremental encoder the VA optical disc uses only incremental and index code tracks The incremental track is structured and read by quadrature sensors in the usual way However neither the encoder nor the host system accumulate incremental counts as the read station traverses Instead the four quadrature states per optical cycle are decoded to control the spatial timing of indexing operations whereby the absolute position information is obtained The index track is coded
4. GURLEY MODEL VS60H VIRTUAL ABSOLUTE ENCODER P MOTION TYPE ROTARY USAGE GRADE J K METROLOGY INDUSTRIAL P q OUTPUT ABSOLUTE C MAX RESOLUTION 2 1 048 576 STEPS REV NATURAL BINARY ABSOLUTE OUTPUT The V860H is a high performance optical encoder that utilizes unique Virtual Absolute technology to combine the opto mechanical simplicity and ruggedness of an incremental encoder with the system reliability and interfacing ease of an absolute encoder This encoder has been designed for quasi military applications such as radar pedestals and tracking mounts Custom resolutions available up to 24 bits Please contact factory for more information d ingenui Gurley Precision Instruments Isa 514 Fulton Street 9001 Troy NY 12180 U S A 800 759 1844 518 272 6300 fax 518 274 0336 CERTIFIED Online at www gurley com e mail info gurley com SPECIFICATIONS Resolution 270 1 048 576 words rev Installed Accuracy 1 5 arcs including quantization amp coupling errors Initialization angle 0 308 Output code Parallel natural binary Output device TTL compatible tri state buffer registers Max data update rate 1 MHz Parity Odd Shaft direction for increasing count Clockwise looking at bellows end Input power 12Vdc 0 5V 375 mA max Illumination source LEDs screened and derated for 100 000 hr life Max
5. PLACES EQUALLY SPACED ON A 4 250 8107 95 B C ENCODER HOUSING BLK WHT BLU WHT 2 697 0 010 68 50 0 25 2 45740 010 62 41 0 25 pe 2 445 62 10 REF 2 207 56 06 REF 4 40 X pal SKT HO CAP SCR SST 6 4 FL WASHER SST 6 6 32 X 5 8 SKT HD H 1 venne Z gmp 3 665 93 09 390 111 51 1 500 38 10 3 000 176 20 24 en Gurley Precision Instruments N S 6 go H 514 Fulton Street Troy NY 12180 U S A PAGE 7 OF 8 800 759 1844 518 272 6300 fax 518 274 0336 v3 1 Online at www gurley com e mail info gurley com ORDERING INFORMATION MODEL RES FORMAT INT BASE CAB EXIT CONN DIA TEMP SPEC V860H 16384 RES FORMAT INT BASE CAB EXIT CONN DIA TEMP SPEC 16384 P 06 A XX 48 OU 40E Zt D gt 06 a T jw a Disc resolution lines Parallel natural binary output 6 bits of internal interpolation Standard base amp mounting configuration Cable length inches 48 inches standard Top exit cable Pigtails DA 15P power DC 37P data 2 5 in dia through hole shaft 40 C to 85 C operating temperature range Issued at time of order to cover special customer requirements No special features ACCESSORIES order separately DX00432 SPECIAL CAPABILITIES Bellows type shaft coupling For special situations we can optimize catalog encoders to provide
6. accuracy misalignments should be kept as small as possible 83 3P 3E 0 14A lt 1 0 P Parallel offset inches max 0 012 E Axial extension or compression inches max 0 336 A Angular misalignment degrees max 7 Parallel offset P is equal to the total offset between the centerline of the encoder and the centerline of the user s shaft plus half the radial runout TIR 2 of the user s shaft Table 1 Power Pin Connections DA 15P Pin Name Type Description 1 GND Power Ground power supply common 2 GND Power Ground power supply common 3 4 GND Power Ground power supply common 5 GND Power Ground power supply common 6 12 Power Single 12VDC supply regulated to 5VDC internally 7 8 9 GND Power Ground power supply common 10 11 12 GND Power Ground power supply common 13 12 Power Single 12VDC supply regulated to 5VDC internally 14 12 Power Single 12VDC supply regulated to 5VDC internally 15 PIN 1 PIN 8 SIS PIN 9 PIN 15 VS60H PAGE 5 oF 8 V3 1 READOUT TIMING REQUIREMENTS The read cycle is initiated by bringing the Interrogate line low The data will be valid 750nS after the falling edge of INT Synchronicity of all data transitions cannot be guaranteed in any device with natural binary output The output buffer register is provided to avoid reading out a mixture of old and new data bits when sampling the output
7. at the exact moment position data is changing oO N Angular Misalignment A 0 8 6 4 2 m x n 3 E G E a 2 gt E La Ku a d 2 3 Axial Extension or Compression E inches ELECTRICAL CONNECTIONS If the V860H is ordered with connector code P the three cables are terminated in pigtails the wire colors are shown on the dimension drawing on page 8 If it is ordered with connector code D the cables are terminated in two connectors a DA 15P which contains all the power leads and a DC 37P with all the data Connector code D interfaces with any cable harness designed for Gurley s discontinued model 60 25H conventional absolute encoder which had an external electronics package Since the V860H does not have a separate electronics package the cable and connectors coming from the encoder are wired and polarized to imitate the previous electronic package connectors Blanks in the pinout tables below signify pins which are not connected to anything inside the encoder The power interface connector mates with a standard DA 15S D subminiature connector with spring latches 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 SPECIFICATIONS Table 2 Data Pin Connections DC 37P Pin S Name Type Description CR O 6 DO9 Output Dab y 8 D13 Output Da
8. differently from a conventional incremental encoder On the index track an Opaque or transparent region exactly one optical cycle wide aligns correspondingly with every opaque transparent line pair in the adjacent incremental track Around the full circumference of the disc any given index mark is equally likely to be clear or opaque The bit sequence into which the index marks will be translated by the detector dedicated to this track is pseudorandom Absolute position is encoded serially in this one track rather than in parallel over many tracks This simplifies optomechanical alignment compared with traditional absolute encoders A 14 bit VA employs a sequence of 16384 indices These are decoded for cycle position to which 6 bits of interpolated position within the cycle are appended Every possible grouping of 14 consecutive indices in the sequence is unique due to the non repeating design of the code Every optical cycle of the incremental timing track is thus tagged by a unique 14 bit code whose first bit is immediately adjacent to the cycle and whose remaining 13 bits trail behind This arrangement is sometimes called a chain code Because the coding sequence is such that each 14 bit code tag shares 13 bits with its neighboring tags to the left and right in overlapping fashion one might conclude that the code progression is monostrophic like Gray code with only one bit differing between consecutive tags Not so While adjacent tags share all but
9. ing for a full tag to be acquired e Search mode Having acquired a complete new tag from an initialization sweep it may be busy pinpointing the absolute position of the new tag in the overall code sequence How long this tag search will take depends on specific design characteristics of the decoder including its 16 MHz clock speed It also depends on how far away the read station happens to be from the starting point of the search and whether the decoder is chasing the axis position from behind as italso moves during the search In the worst case scenario a 14 bit tag search will take about 4mS e Track mode It may be decoding all new indexing code tags obtained from the read station satisfactorily validating the code bit wise as it s detected and providing reliable absolute position information i e tracking the motion input in servo fashion If scale contamination or overwhelming electrical noise should invalidate the index signal or even the proper operation of the decoder itself this will result in a reported fault e Proper quadrature sequence is verified at all times Since this could corrupt the tag bit due to improper sample timing the decoder resets and awaits a fresh tag e Successors to a false tag will survive very little following motion of the disc before faulting due to the non repeating nature of the code sequence e A supply voltage supervisor and power up reset IC is included to reset the decoder if the power supply dip
10. one bit the positions of all the shared bits within the tags are shifted Tags which truly differ by only one bit are located in seemingly random sections of the scale Improperly decoded tags would therefore result in gross position errors Partly for this reason a sophisticated sequence verification capability is an integral part of GPIl s proprietary Virtual Absolute tag decoder design On power up absolute position is unknown An initialization procedure is executed to obtain a complete tag for decoding There are ways to build a pseudorandom encoder so that absolute information is available on power up without initializing but these techniques require far more complex sensing hardware they often impose slower operation as well And none of them offers the sophisticated built in testing of GPI s Virtual Absolute technology Because the index track is viewed by a single sensor the read station must be bumped in either direction or wiggled in both to cover a minimum net angle In this case a net motion infinitesimally less than 14 optical cycles guarantees 14 major cycle boundaries of the incremental timing track will be crossed This corresponds to 0 308 maximum initialization traverse from any starting position of the disc Discs with higher line counts require shorter initialization traverses but are correspondingly more difficult to install and align Cycle boundary phasing with respect to the index marks is such that indices are sampled only a
11. s below 4 70VDC measured locally inside the encoder Most fault conditions may be cleared by re executing the initialization procedure In the case of disc damage or fouling the host system may measure the affected region by approaching it from alternate directions and observing the Status bit reporting the validity of the absolute position output The Status bit offers a simple mechanism for a microprocessor based host system to quickly assess data validity If the tag decoder detects a fault condition and is waiting for an initial tag sweep or while it is still engaged in a tag search the Status bit will be set to a logic 1 signifying the current output value is invalid and position is unknown Foramore thorough discussion see the V860H User s Manual Gurley Precision Instruments VU S 6 g H 514 Fulton Street Troy NY 12180 U S A PAGE 4 OF 8 800 759 1844 518 272 6300 fax 518 274 0336 v3 1 Online at www gurley com e mail info gurley com SPECIFICATIONS Offset Position WWW A True Position Offset Position SHAFT COUPLING The optional precision flexible metal bellows assembly P N DX00432 compensates for small angular misalignment axial extension or compression or parallel offset in the installation without affecting bearing or bellows life Keeping the misalignments within the following constraints will assure infinite life of the coupling but will introduce some error To preserve the encoder s
12. t their centers i e spatially timed For this reason the incremental track is sometimes called the timing track This arrangement has two important benefits e s with conventional incremental encoders the readout accuracy linearity of the VA encoder depends only on the regularity of its incremental track lines These are easy to create on the disc with precision and easy for the quadrature detectors to read accurately through slit gratings that average out microscopic optical printing imperfections and moderate amounts of contamination This also results in healthier signal amplitudes Conventional absolute encoders have difficulty employing a similar optical averaging technique to improve readout accuracy and signal to noise ratio e The serial indices which must be viewed through a single mask aperture like a conventional absolute rather than through a grating are at their maximal light or dark conditions when sampled This ensures the greatest electrical noise margin immunity to contamination and tolerance of misalignment between disc and read station Unlike a conventional absolute encoder the exact angular position of the transition between light and dark has no effect on decoding reliability or accuracy Gurley Precision Instruments VU S 6 o H 514 Fulton Street Troy NY 12180 U S A PAGE 3 OF 8 800 759 1844 518 272 6300 fax 518 274 0336 v3 1 Online at www gurley com e mail info gurley com THEORY OF OPERATION
13. ta bit Cd 9 D15 f Output Databit_ CCCiCCid OB oo o Et Ooa o S T y O o G T y Oa o G e y a ee 20 DOO Output Data bit MSB weighted 1 2 revolution i 23 DO6 Output Data bit i y Clear falling edge clears fault flip flop Output Fault 1 chain code or quadrature error detected amp stored 320 Offset make current position equal zero Interrogate copy current position to output buffer register BEES H H H LT Ground power supply common PIN 1 PIN 19 nf O O000000000000000000 O 9900000000000000090 N LC PIN 20 PIN 37 The data I O interface connector mates with a standard DC 37S D subminiature connector with spring latches Gurley Precision Instruments VU S S U H 514 Fulton Street Troy NY 12180 U S A PAGE 6 OF 8 800 759 1844 518 272 6300 fax 518 274 0336 v3 1 Online at www gurley com e mail info gurley com COUPLING DETAILS 8 32 UNC 28 THO X 1 4 6 4 DP 468 11 89 TYP 4 210 106 93 SN Leas ae SHAFT 3 750 95 25 250 6 35 2 5000 0002 63 500 005 125 3 18 lt x 1 8 gA DP THIS END 1125 3 18 _ 92 505 663 63 REMAINING LENGTH 093 2 36 2 29 ine j OT 1427 1 HOUSING PILOT 96 00 6152 4 95 80 9147 3 95 24 9133 1 i I 1 10 32 UNF 2B THD X 3 8 9 5 DP 4 PLACES EQUALLY SPACED ON A 95 250 133 35 B C ENCODER HOUSING DUST SHIELD MOUNTING HOLES 4 40 UNC 2B THD X 22 5 6 DP 6
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