The example program below uses analog input 0 as the feedback from the temperature sensor and analog
output 0 as the control voltage to the heater. An update rate of 25msec was set using the CL command, but a
slower update rate could have been chosen due to the slow nature of temperature response. The PID values
entered were experimentally found to provide optimum results based on the system. The desired set-point
was chosen as 1V. A dead-band of 0.1V was added in order to prevent the system from responding to minor
disturbances of the sensor.
#PCL
CL 25;
'25msec update rate
AF 0;
'analog input 0 as feedback
AZ 0;
'analog output 0 as control
KP 1;
'proportional gain to 1
KD 10;
'derivative gain to 10
KI 0.5;
'integral gain to 0.5
DB 0.1;
'deadband of 0.1V
PS 1.8;
'set-point at 1.8V
Note: When the Process Control Loop is enabled, the Analog output voltage is normalized to half of the total
voltage input. For instance, with a 0-5V analog input range such as the RIO-47100 – the voltage is
normalized to 2.5V. This allows the output to go below 2.5 to compensate for a negative error and above
2.5V to compensate for positive error.
The AQ and DQ must be set on the RIO-47120 to configure the Analog input and output ranges before the
process control loops are run and prior to setting AZ & AF. The range of the PS command is dependant on
the AQ command.
Current vs Flow Control Mode
The PID loop on the RIO-47xxx by default works as a “current” mode loop. This means that when position
error is 0 the analog output will also be set to zero.
Firmware revisions Rev D and newer allow the user to set a negative value for the DB command that will set
the Process control loop into a flow control or velocity mode. When DB is set to a negative value, the analog
output will be held at its current value and the PID’s will be held constant when the feedback is within the
range set by the DB command. This mode is preferable for many fluid and temperature control applications.
48 Chapter 4 I/O
RIO-47xxx
Содержание RIO-47**0
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Страница 93: ...RIO Dimensions RIO 471xx Units in centimeters RIO 47xxx Appendix 87...
Страница 94: ...RIO 472xx Units in millimeters 88 Appendix RIO 47xxx...
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