ECT 464 Lecture 6a Analog I/O

Today’s Quote: A marriage may be made in heaven, but the maintenance must be done on earth. However, each one of you also must love his wife as he loves himself, and the wife must respect her husband. Ephesians 5:33

Analog Input Devices We don’t use special instructions to input and output analog values. Ports treated as specialty I/O Analog values are 16 bit signed integers (SLC-500) Analog Inputs and Outputs vary by PLC type and card +/- 10 V +/- 5 V 0-5 V 0-10 V 4-20 mA 0-20 mA +/- 20 mA 1-5 V Single vs. Differential

Analog Measurements Position Speed Acceleration Weight Flow Level Pressure Temperature Distance Light

Analog Outputs Speed Valve Position Analog Meter Chart Recorder

Analog Input Addressing I:3.0 Analog Input 0 I:3.1 Analog Input 1 I:3.2 Analog Input 2 I:3.3 Analog Input 3 8 bit analog input Bit 15 is always 0

Analog Output Addressing I:1.0 Analog Output 0 I:1.1 Analog Output 1 8 bit analog input Bit 15, and 0-6 is always 0 MVM (Move with Mask) instruction is used with a mask of 7F80h to move data to the output words

Analog Control Loops Output = (Input-Feedback)*Gain Output = (Input-Feedback)*Gain

Analog Control Characteristics Steady State Error Steady State Error Gain only is adjustable Gain only is adjustable Critical gain Critical gain Damping response Damping response Oscillation frequency Oscillation frequency