Quantcast BINARY ANGULAR MEASUREMENT

 
  
 
the greatest weight is the most significant bit (MSB). The bit with the least weight or representing the smallest value is the least significant bit (LSB). Natural binary code is used in a system of digital data transmission and conversion called  binary  angular  measurement (BAM). Other coding systems such as  Gray code and binary-coded   decimal   (BCD)  are  also  used  by analog-to-digital converters. BINARY ANGULAR MEASUREMENT. Binary  angular  measurement  words  (BAMs)  are standardized binary words used to transfer angular measurements between shipboard tactical data system equipments. BAM data words are used to transfer quantities  between  digital  equipments,  from  digital equipments to D/A converters, or from A/D converters to digital equipments. BAM  data  words  are  specifically  designed  to indicate up to 360 degrees of angular values in binary form, often in  steps or increments  of as small as 0.009766 degree (the LSB value). Figure 13-3 shows one example of a BAM word. This 12-bit word (2°-211) can indicate 360 degrees of angle in steps of 0.088 degree. The LSB is equal to 0.088 degree when set (ONE), while the MSB is equal to 180 degrees when set. When all 12 bits are set, a maximum angle of 359.902 degrees is indicated. ZERO or 360 degrees is indicated when all bits in the BAM data word are clear (ZEROS). BAM words are also used to transmit non-angular values such as range or height. When non-angular values are being used, the LSB value indicates the smallest  step  or  increment  of  the  quantity  being transmitted.  The  MSB  value  represents  half  the maximum value that may be transmitted. The sum of all bits when set indicates the maximum quantity that can  be  transmitted.  This  corresponds  to  the  0-  to 360-degree  capability  of  common  shipboard  synchro systems. GRAY CODE. —Gray code or reflected binary code is used in devices where a transition from one consecutive value to another takes place, such as angular  measurement  and  encoding.  The  code  is designed to change from one value to the next with only one bit change. Table 13-1 shows the relationships between Gray code, BCD, and natural binary code. BINARY-CODED DECIMAL (BCD). —BCD represents decimal values with a 4-bit code, called the 8-4-2-1 code. Each of the 4-bit groupings represents one decimal digit. BCD encoders allow for immediate decimal display of the converter output. They are found in such devices as digital voltmeters and other types of decimal  display  devices.  Table  13-1  shows  the relationships  between  BCD,  Gray  code,  and  natural binary  code. SYNCHROS Up to this point, we have discussed basically single-phase analog data signals. One of the most common  shipboard  analog  signals  requiring  conversion is the 3-phase or 5-wire synchro signal. Synchros are used throughout naval ships for the rapid transmission of  analog  information  between  equipments  and stations. They are found in just about every weapon, communication,  underwater  detection,  and  navigation system  in  use  in  the  Navy.  Numerous  kinds  of information  involving  angular  displacement  or ranges of values  are transmitted. For the combat direction  system  (CDS)  equipments  to  use  this information, the synchro signals must be converted to their digital equivalent. The following information provides a limited overview of synchros as they apply to   digital   systems   and   synchro-to-digital   (S/D) conversion. Figure  13-3.—A  12-bit  binary  angular  measurement  (BAM)  word. 13-4

 


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