Unit 13 A plc revision

 Convert the binary number 10111101 to decimal

• 174

• 189

• 157

• 182

Convert the decimal number 146 to binary

• 10010001

• 10010011

• 10010010

• 1001100

Convert the decimal number 124 to hexadecimal

• 18

• 9

• 6c

• 7c

The majority of PLCs work using the refresh or batch process mode. This involves the PLC in a continuously repeating scan cycle of copying the status of all inputs to memory, working through the stored program and then updating the outputs. Give TWO significant limitations of this process:

How many binary bits are needed to store the BCD number 1375? 

• 1=001

  3=011

  7=111

  5=101

  16bit

• 1=0001

  3=0011

  7=0111

  5=0101

  16bit

• 1=0011

  3=0001

  7=0111

  5=0101

  8bit

• 1=0001

  3=0011

  7=111

  5=101

  8bit

A PLC system has an input filter delay of 5ms, relay outputs with a quoted delay of 8ms and, when monitored, the program scan times are 12ms minimum and 32ms maximum. For a given input change calculate the best case AND worst case response for an output directly controlled by that input: Marks 

• Min = 24ms

  Max = 78ms

• Min = 25ms

  Max = 29ms

• Min = 25ms

  Max = 77ms

• Min = 26

  Max = 82