3.3.2 Alarm blocking at the beginning of power on
Sometimes the fault alarm may occur at the beginning of power on. In a heating system, at the
beginning of power on, its temperature is much lower than the set point. If low limit and deviation
low limit are set and the alarm conditions are satisfied, the instrument should alarm, but there is no
problem in the system. Contrarily, in an refrigerating system, the unnecessary high limit or deviation
high limit alarm may occur at the beginning of power on. Therefore, AI instruments offer the function
of alarm blocking at the beginning of power on. When Act is set to rEbA or drbA, the corresponding
low or high alarms are blocked until the alarm condition first clears. If the alarm condition is satisfied
again, the alarm will work.
3.3.3 Communication function
S or S4 module can be installed at COMM slot to communicate with a computer or the Modbus
master device through RS485 network.. The instrument can be controlled by computer. AI
instruments can be connected to the computer through RS232 or USB communication port(with
RS232 to RS485 or USB to RS485 converter). Every communication port of a computer can
connect up to 60 AI instruments, or 80 AI instruments if a repeater is installed.
A computer with 2 communication ports can connect up to 160 instruments. Please note that every
instrument connecting to the same communication line should be set to a unique communication
address. If the number of instrument are enough, 2 or more computers can be used and a local
network can be set up.
AIDCS application software(Not free), a distributed control system software developed by Rievtech,
can control and manage 1
～
160 AI instruments, record the data, generate and print reports. If users
want to develop their own distributed control system by themselves, the communication protocol of
AI instruments can be free offered. There are many famous distributed control system software
support AI instruments.
Communication protocol
AIBUS is the communication protocol designed for AI-series displaying and controlling
instruments.It functions by easy instructions and is characterized by the function of setting and
reading parameters at the same time. Thus, Circle Time is not damaged while setting parameters.
With its shorter instruction length, AIBUS has quicker rate than MODBUS( especially when setting
instruction in MODBUS, it cannot be read meanwhile since circle time will be influenced and
prolonged). AIBUS has system control ability to construct large scale process. It exploits 16 bit
SUM correcting code, operates with higher speed and more reliable communication since
it supports 9600, 19200 and other wave frequencies. With 19200, the average time for an upper
computer to visit a high performance controller like AI-5 series is 40mS.
One RS485 is allowed to connected with up to 80 pc of controllers ( to promise the reliability of
communication, one RS485 repeater is added when over 60 pc). AI sereis controllers can be
connected with touch screen and PLC with full resource and higher speed. PC is widely used when
under WINDOWS operation environment for its conveniece and powerful function. The application
of the latest Industrial PC touch screen further brings a new environment to industrial automation.
This results in the much lower cost and much higher performance of controllers+PC much than that
of the traditional DCS.
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