Analogue Inputs Resolution Assignment

Transcription

1 Analogue Inputs Resolution Assignment a) Describe the relationship between the number of bits used in an analogue signal and the resolution available. b) A system has a level sensor which measures the level of water in a tank. It provides -1V signal which is read by a 12 bit A-D converter. Given the system has a stroke of 25mm, calculate the minimum increment in the height of the water that the system can discern. LO2.2

2 Analogue Inputs - Resolution The resolution, the smallest change that an Analogue input can detect, is determined by how many binary bits the A-D converter has. If we read a 1v signal and we only have 1 bit signal V PLC A-D

3 Analogue Inputs - Resolution The resolution, the smallest change that an Analogue input can detect, is determined by how many binary bits the A-D converter has. If we read a 1v signal and we only have 1 bit signal 1V PLC A-D 1 States 2, steps 1 Resolution 1V

4 Analogue Inputs - Resolution The resolution, the smallest change that an Analogue input can detect, is determined by how many binary bits the A-D converter has. If we read a 1v signal and we only have 2 bit A to D converter V PLC A-D Bit 1 Bit

5 Analogue Inputs - Resolution The resolution, the smallest change that an Analogue input can detect, is determined by how many binary bits the A-D converter has. If we read a 1v signal and we only have 2 bit A to D converter 3.33V PLC A-D Bit 1 Bit

6 Analogue Inputs - Resolution The resolution, the smallest change that an Analogue input can detect, is determined by how many binary bits the A-D converter has. If we read a 1v signal and we only have 2 bit A to D converter 6.66V PLC A-D Bit 1 Bit

7 Analogue Inputs - Resolution The resolution, the smallest change that an Analogue input can detect, is determined by how many binary bits the A-D converter has. If we read a 1v signal and we only have 2 bit A to D converter 1V PLC A-D Bit 1 Bit States 4 steps 3 Resolution 3.33V

8 Analogue I/O Resolution 4 bit binary enables us to count to 15 Bit 3 Bit 2 Bit 1 Bit Analogue Voltage V max = 1V States 16, steps 15 resolution 1V/15 steps =.66v

9 Analogue Inputs - Resolution The resolution, the smallest change that an Analogue input can detect, is determined by how many binary bits the A-D converter has. If we read a 15v signal and we now have 12 bit A to D converter 15v PLC A-D

10 Analogue I/O Resolution Step size is 3.66mV 12 bit binary enables us to count to.495 Bit 11 Bit 1 Bit 9 Bit 8 Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit Analogue Voltage V max = 15V mV mV mV 1 etc v

11 Analogue I/O Resolution 12 bit binary enables us to count to 495 Step size = V max There are 496 different states But only 495 steps between them. V max = 15V then step size (resolution) is 15/495 = 3.66mV

12 Analogue I/O Resolution 16 bit binary enables us to count to? Step size = V max There are...different states But only... steps between them. V max = 1V then step size (resolution) is 1/ =

13 Analogue I/O Resolution 16 bit binary enables us to count to 65536? Step size = V max There are different states But only steps between them. V max = 1V then step size (resolution) is 1/65535 =.152mV

14 Example Question a) Describe the relationship between the number of bits used in an analogue signal and the resolution available. b) A system has a level sensor which provides 1 bit -1V signal and measures the level of water in a tank. Given the system has a stroke of 5mm, calculate the voltage change per step and the minimum increment in the height of the water that the system can discern.

15 Example Question b) A system has a level sensor which provides a 1 bit -1V signal and measures the level of water in a tank. Given the system has a stroke of 5mm, calculate the minimum increment in the height of the water that the system can discern. Vmax/2 1-1 = 1/123 =.97v per step 5/123 =.488mm End

16 Analogue Inputs - Resolution The resolution, the smallest change that an Analogue input can detect, is determined by how many binary bits the A-D converter has. 6.2v PLC 12 bit A-D (-1V output)

17 Analogue I/O Resolution 4 bit binary enables us to count to 15 Bit 3 Bit 2 Bit 1 Bit Analogue Voltage V max = 15V Step size = There are 16 different states V max But only 15 steps between them.

18 Analogue I/O Resolution Digital to Analogue Conversion Four bit binary number Analogue -15V v Digital 4 bit

19 Analogue I/O Resolution Digital to Analogue Conversion Four bit binary number Analogue -15V 1v 1 Digital 4 bit

20 Analogue I/O Resolution Digital to Analogue Conversion Four bit binary number Analogue -15V 1 2v Digital 4 bit

21 Analogue I/O Resolution Digital to Analogue Conversion Four bit binary number Analogue -15V 1 3v 1 Digital 4 bit