ANALOG DEVICES Solid State Control Differential Transmitter SCDX/REDX1623 FEATURES Accuracy is +4 Arc Minutes 14 Bit Resolution Small Size 3.125 x 2.6 x 0.8 Low Power Dissipation 1.5 Watts Mil. Spec. Versions Available DESCRIPTION The SCDX/RCDX Series are solid state control differential transmitters. Their function is analogous to an electro- mechanical CDX except that the mechanical input of the CDX has been replaced by a binary input angle. The solid state differential transmitter accepts a digital angle input together with either a 3 wire synchro (SCDX) (or 4 wire resolver; RCDX) angle input and gives as output synchro or resolver signals representing the difference between the two input angles. Thus the outputs can be described by A sin wt sin(@ 9) and Asin wt cos(@ ) where 0 represents the synchro or resolver input angle, represents the binary input angle (14 bits) and w is the synchro excitation frequency. The outputs from the SCDX resemble in their function the out- puts from a conventional resolver but they are not transformer isolated. The outputs are from a pair of operational amplifiers (5.0 volts rms at maximum) which can be fed into a power amplifier and Scott transformer to provide either 3 wire synchro or 4 wire resolver outputs at appropriate voltage levels. Both 60Hz and 400Hz versions of the SCDX series are available. The 400Hz modules have the input transformers contained inside the module for either synchro or resolver inputs. The SCDX modules for use on 60Hz do not contain the input transformers; suitable external transformers are available for either synchro or resolver inputs. These transformers are designated STM 1671/XYZ or RTM 1671/XYZ where the X, Y and Z signify the temperature and voltage conditions. 13 14 BIT DIGITAL tNPUT 1 7 s1 1 _ __ 581 = ASINGI SING oF ASIN G1 SING. i ASINw1 SIN Ui. ot ll $3 RCODX 1623 | ____+ _ A SIN wt COS 0 fern 82 = ASIN wt SIN Go + 120%) ' Q ASINGtCOSIG-0) oF 1 T pi? $3 = A SIN ut SIN - * 2469) Lee LI Figure 7. SYNCHRO & RESOLVER CONVERTERS VOL. Il, 13-45SPECIFICATIONS (typical @ +25C: and +15V unless otherwise noted) Accuracy* Resolution Digital Inputs Digital Input Levels +4 arc minutes 14 bits (1 LSB = 1.3 arc minutes) 14 bits natural binary TTL, DTL Digital Input Loading Response Time to 180 digital or synchro input step 3 TTL loads 300 micro seconds Signal Inputs Signal Impedance Resolver 5.0 volts 400Hz Synchro 11.8 volts rms 400Hz Resolver 11.8 volts rms 400Hz Resolver 26.0 volts rms 400Hz Synchro 90 volts rms 60Hz or 400Hz Resolver 90 volts rms 60Hz or 400Hz Resolver 115 volts rms 60Hz or 400Hz Low level 20K ohms L-L High level 200K ohms L-L Transformer Isolation Output Voltage Carrier Phase Shift Power Supplies $00 volts DC 5 volts rms into 2K ohms (min) Less than 1 degree +15 volts at 45mA -15 volts at 45mA +5 volts at 20mA Operating Temperature Range -55C to + 105C oF 0C to +70C Storage Temperature Range -55C to + 125C Warm up Full accuracy upon switch on Dimensions 3.125" x 2.525" x 0.8" 79.4mm x 66.6mm x 20.5mm Weight 7 0z. (200 g:aims) "Note: Accuracy spplics over operating temperature range and for a) +10% signal amplitude variations b) 10% signal harmonic distortion c) 410% signal frequency variation d) 5% power supply variation Specifications subject to change without notice. PRINTED CIRCUIT CARDS FOR SCDX/RCDX 400Hz AND 60Hz MODULES Printed circuit cards are available for both the 400Hz and the 60Hz SCDX or RCDX modules. In the case of the 400Hz versions of the SCDX or RCDX the input transformers are contained inside the modules which are mounted on the smaller printed circuit card. For 60Hz use the input transformer module is mounted on the printed circuit card. The edge connections are shown in table ] the connections are 22/22 way 0.156 pitch. (Pin 3, i.e. Sy is only used on AC 1656 in which case it is connected to W.) The card type numbers are AC 1637 for mounting the 400Hz module and AC 1656 for mounting the 60Hz module and its transformer unit. PINS-040%001"DIA BRASS,GOLD PLATED, 2 yd 2.625" 212 2-20" | (csp) 140 3d 120 | 1 os3 10 9 82 TOP VIEW 9 o 9os1 8o- -36 +15 76 @ GND 6Q : 50- - SV 4 o- ?*8) SCDX1623. 0 97 oO SINE o- -ocos - 1 5 (ms) Figure 2. 400Hz SCDX Module 2, 0-8" . 2-625" 212; 2-20" >| 1-0" 3.125" TTVUTISI ma GeitcHes oF -4"= 2-4" eo | wager ee GO TOP VIEW w oS @ R Ss 82. $I TOP VIEW | STM1671 | N.C. N.C. NAC. Nc UT: SCDX1623 pba ----G-- - +b---9- 4 __ . _2 PITCHES 9-8", | 2PiTCcHEs oes 8 OF. eB Figure 3. STM 1671 and 60Hz SCDX Modules VOL. I 13-46 SYNCHRO & RESOLVER CONVERTERSApplying the SCDX/RCDX1623 USE OF THE SCDX AND RCDX The inputs to the SCDX are two angles one as either resolver or synchro wires and the other in digital form. The output from the SCDX or RCDX is from operational amplifiers giving 5 volts RMS capable of driving into loads of 2K ohms or more and it is in resolver form. The output can in some cases be used directly or via a directly connected Scott transformer to convert to synchro three wire data. The output magnitudes represent the sine and cosine of the difference between the input angle and the digital angle. CONNECTIONS The SCDX modules can be used for either synchro or resolver use and in each case they can be used at 400Hz or 60Hz. 400Hz operation. In the case of 400Hz operation the input transformers are contained inside the SCDX module or RCDX module. The internal connections are different for the resolver and synchro use but in both cases the input pins marked S,, S2 and 3 are used for the signal voltages. For resolver use S$, is the sin input, S, is the cosine input and S3 is the common connection. For synchro use the signals are applied to the pins S,, 8, and 83 in rotation. The distinction between the modules is in the marking RCDX or SCDX. Different signal voltage levels are accommodated by different transformer windings and are determined by the number representing Z in the ordering code; see the back page for details. A diagram showing the pin arrangement for the 400Hz version of the SCDX and RCDX is shown in Fig. 2. 60Hz operation. In this case the signal input uses four pins to the SCDX or RCDX modules which will be marked QRST, these pins take in resolver format signals (2 volts rms max.) Pin T is common, S is plus cosine, R is plus sine, and Q is minus cosine. The pins QRST on the RCDX or SCDX module must be connected to the pins QRST on the transformer module, i.e. Q>Q etc. In the case of 60Hz synchro use the inputs must be applied to the pins marked S,, S. and S3 on the transformer module. In the case of 60Hz resolver use the sine input must be applied between S, and S, and the cosine input between S, and W. (The sense of the connections is such that if W and S, are regarded as common then S, and S9 will be in time phase with each other in the first quadrant.) No reference input is used in this module. A diagram showing the SCDX module and the STM 1671 transformer module pin arrangement and marking is shown in Fig. 3. Warning /n no circumstances should the synchro or resolver voltages be connected directly to the pins marked QRST. The outputs are directly available frorn the module on the pins marked sine and cos. Pins | to 14 are the TTL digital angle input pins, pin | is the MSB (180). The power supplies and ground are as shown in Fig. 2. The power supply lines should not be reversed. punwo ft [2/3/44 15(617] 8] 9 |10/99[t2 (13 [14{15| 16/17] 18/19 nc{Nc|wcjNc|Nc |S, FUNCTION ' S4)S3|S2}NC AJBIClOLE, FI Als [KP ty MP NP PLA PST TP ULV Wwe xy 2 FUNCTION |NCINC WC co Nc +8 nc (NC TABLE 1. Edge Connections for Cards AC1637 and AC1656 When Used to Hold SCDX or RCDX Modules BIT WEIGHT TABLE Bit Number Weight in Degrees | (MSB) 180.0000 2 90.0000 3 45.0000 4 22.5000 5 11,2500 6 5.6250 7 2.8125 8 1.4063 9 0.7031 10 0.3516 11 0.1758 12 0.0879 13 0.0439 14 0.0220 APPLICATIONS The SCDX so far described has an input angle @ from Synchro lines and a digital input angle , the output is either resolver or synchro signals representing the angle (@ ). Alternative types of SCDX are available in which the output due to the input angles @ and is synchro or resolver signals representing (9 +). With the availability of SCDX units which can either add or subtract the input angles a greater flexibility of application is available. A common and obvious application for the SCDX is to add computer provided angular information to synchro wires. The example of application shown here has been chosen to show how apart from coupling in and out of computer systems, the advent of angle to digital conversion and visa versa has generated applications which do not have simple electromechanical equivalents. L INPUT _ OUTPUT 1623 SCDX 1623 () (2) m SOCI Figure 4. Gear-Box Using SCDX Modules Fig. 4 Shows three interconnected modules i.e. two SCDXs and one synchro to digital converter. The inputs and outputs are either three wire synchro or four wire resolver signals. Modules interconnected in this way are used to give the electrical equivalent of gear changing. K represents the angular rotation of the input signals, L represents the angular rotation of the signals coupling the output of SCDX (1) to the input of SCDX (2) and M represents the angular rotation of the output signals. The coupling between the 16 bit synchro to digital converter and the SCDX (1) has been offset by n bits from the M.S.B. As a result of this the rotation L will be given by: L=K + 2K----(1) In (1) the plus or minus sign will depend upon whether the SCDX (1) is of the type that gives out @ + or 0 6. The interconnections between the synchro to digital converter and the SCDX (2) have also been staggered by m digits from SYNCHRO & RESOLVER CONVERTERS VOL. Il, 13-47the M.S.B. and this means that M wil! be given by: -- M=L+ 2K-~----(2) again the plus or minus sign will depend upon whether the SCDX (2) adds or subtracts. Combining (1) and (2) gives, M=K(1+ 29 + 2) For n and m up to 3 all the odd ratios from 3 -- | to 17 -- 1 are possible. For n = O (i.e. direct connection) using an adding SCDX (1) and the non-binarv even ratios 6 and 10 are obtained for m = 2 and m = 3. Higher ratios can be obtained at the expense of angular resolution by taking n and m greater than 3. If in Fig. 4 the staggering of the interconnections is reversed ie. the M.S.B. on the synchro to digital converter is connected to the second M.S.B. on SCDX (1) reduction ratios can be obtained but there will be severe limitations on the total output excursion in angle due to the saw toothed behaviour of the input information to the SCDXs. This difficulty can be overcome by using the system of Fig. 4 in a feed-back loop. Showing the unit of Fig. 4 as a step up ratio box N in Fig. 5 an alternative method of speed reduction is obtained. With such a system however instability may occur unless the frequency response characteristic of the synchro to digital converter in Fig. 5 is shaped for the particular ratio. enbestegtess {rend nchroto igital Converter B SCDX Figure 5. Reduction Gearing Using Step Up in the Feedback Path In Fig. 5 K is the input angle L is the cutput angle, N is the step up ratio, and the following hold: -- M=LN L=K--M =K-LN _ Kk L=TSN giving a ratio of 1 + N. The problem of shaping the frequency response of the synchro to digital converter or putting some dominant lag around the loop should not be overlooked. An interesting application of the SCDX occurs in providing a focal method of deviating or biasing a controlled system, for example a radar antenna. Fig. 6 shows a system for controlling an output rotation from a digital input. The unit marked SSCT is a solid state control transformer which is another module produced by Analog Devices. This module, the SSCT, is the equivalent of its electromechanical counterpart. It has as inputs an angle in synchro format @ and a control angle @ in digital form. It gives out a carrier voltage with an amplitude proportional to sin (0 -- ). By using a phase sensitive detector shown as A and a D.C. motor system the control loop is formed. The output shaft will take up an angle demanded by the digital input angle . VOL. Il, 13-48 SYNCHRO & RESOLVER CONVERTERS DIGITAL INPUT ANGLE yi " L. 1 Error signal ASinwt Sint-@} SSCT an + DIGITAL ANGLE Figure 6. The Use of an SCDX to Produce an Offset Angle Inside a Control Loop If an SCDX is inserted in the loop as shown by the dotted lines, the setting of the output angle will be determined by both the input digital angle @ and the digital angle a, being either the sum or difference according to how the SCDX is connected. The input angle & applies a shift in angle equivalent to altering the mechanical connection between the antenna and the electromechanical control transmitter or adding an angle to the input demand. Such a scheme could be very useful in the initial stages of on site commissioning of equipment. ORDERING INFORMATION The module numbers RCDX 1623 and SCDX 1623 must be followed by a code XYZ defining the requirements in more detail. X signifies temperature range, Y signifies the frequency of operation and Z determines the signal and reference voltage levels. XY and Z must be replaced by numbers following the number 1623 where: = $ signifies temperature range 0 to 70C = 6 signifies temperature range 55C to + 105C | signifies reference frequency of 400Hz = 2 signifies reference frequency of 60Hz = | signifies synchro signal voltage 11.8 volts, reference 26.0 volts (Y must equal 1) = 2 signifies synchro signal voltage 90.0 volts, reference 115.0 volts (Y may equal 1 or 2) = 3 signifies resolver signal voltage 11.8 volts, reference 11.8 volts (Y must equal 1) signifies resolver signal voltage 26.0 volts, reference 26.0 volts (Y must equal |) = 5 signifies resolver signal voltage 90.0 volts, reference 90.0 volts (Y may equal | or 2) signifies resolver signal voltage 115.0 volts, reference 115.0 volts (Y may equal 1 or 2) = 8 signifies resolver signal voltage 11.8 volts, reference 26 volts (Y must equal 1) Z = 9 signifies resolver signal voltage 5.0 volts(SCDX only) CY must equal 1) EXAMPLE: RCDX 1623/5144 is for a solid state control transmitter with resolver inputs, suitable for operation over the temperature range 0 to 70C working at 400Hz with 26.0 volts signal and 26.0 volts reference. N N << KM 1} N ON il + N N N tt a Transformer module. For 60Hz operation the transformer module STM 1671/XYZ is required where the XYZ are as above. Mounting Cards. For plug-in mounting cards order: AC 1656 - for 60Hz units, AC 1637 for 400Hz units