CHAPTER 3: SYSTEM INFORMATION
SNAP PAC R-Series Controller User’s Guide
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•
Ramping
—Some devices attached to analog outputs should not be abruptly stepped
up or down, because a sudden change might damage the equipment or cause other
problems. Instead, you can gradually ramp the device up or down to the desired value.
•
Analog totalizing
—For an analog input, a totalizer accumulates readings by sampling
the input point at set intervals and storing the total value, for example to determine
total flow based on a varying flow rate signal.
Serial Communication
R-series PACs can communicate with serial devices either through the RS-232 connector on
top of the controller (Port 0) or though SNAP serial communication modules on the rack.
The default configuration for Port 0 is communication with a host PC using a modem and
PPP. To communicate with a serial device, first change Port 0’s configuration in PAC
Manager. Here are brief instructions; for more details, see “Configuring Direct
Communication to Serial Devices” in the
PAC Manager User’s Guide
, form 1704.
1.
In PAC Manager’s Inspect window, click Communications and choose Communication
Port Control from the pop-up menu.
2.
For Com Port 0, click PPP in the Control Function field and choose None from the
dropdown list. Click Apply.
3.
Save the configuration to flash memory.
Communication through the RS-232 port is handled through PAC Control commands. See
“Communication Commands” in Chapter 10 of the
PAC Control User’s Guide
.
For additional serial connections, use SNAP serial communication modules. Most serial
modules provide two channels of serial data, typically to interface with printers, scales, chart
recorders, RFID readers, or Wiegand
®
security devices. A Profibus
®
module provides one
channel of data from Profibus DP devices. See the serial module’s user’s guide for details.
PID Loops
Proportional integral derivative (PID) loops are used to drive a variable, often from an analog
input, toward a desired value. The PID monitors the variable, compares it to the setpoint
(the desired value) and calculates an output that will push the variable very close to the
setpoint. Temperature control is a typical application for a PID.
Each SNAP PAC R-series controller can run up to 96 PID loops. PID loops run on the I/O side,
independently from a PAC Control strategy. To use PID loops, configure them in PAC Control
or PAC Manager, and use PAC Control tuning tools for ease in debugging. See Opto 22 form
#1700, the
PAC Control User’s Guide
, for more information.
Additional Features
For information on configuring additional features available in the SNAP PAC R-series
controller, including security, wireless LAN communication, and the use of protocols such as
SNMP, SMTP, and FTP, see the
PAC Manager User’s Guide
.
