Max300-LG : Description - Specifications - Installation Guide
Extrel
Core Mass Spectrometers
Page 13
systems within seconds. Physical access to this communication channel is via an external
chassis that connects to the controlling PC.
Varieties of Modbus communications
The MAX300
™
-LG can be equipped with a Modbus Master fieldbus I/O system capable
of accepting a variety of modules that communicate with external devices. Some possible
I/O options include:
• Analog Inputs: 4-20 mA
• Analog Outputs: 4-20mA
• Digital Inputs: 24VDC
• Relay Outputs: Contact ratings vary with the module installed
4-20 mA
The 4-20mA communications option is used to send or receive data over a loop of wire
where the current in the loop is proportional to the signal being transmitted. This mode of
communications is most often used over long distances, in an environment that might
otherwise induce electrical noise in the cable. Data is scaled so 4 mA represents zero and
20 mA represents full scale. The MAX300
™
-LG software is capable of using this method
to transmit data and instrument parameters to external monitors or controllers. The
software can also use this method to receive parameters or instructions from an external
source.
The software is capable of using this method to transmit data and instrument parameters
to external monitors or controllers. The software can also use this method to receive
parameters or instructions from an external source. Physical access to this communication
channel is via an external chassis that connects to the controlling PC.
Digital I/O
The Digital Output in the Digital I/O communications option controls the state of relays
the user can connect to external alarms, monitors, controllers or other devices. The
triggers controling these relays can be various types of alarm conditions or instrument
parameters. A common relay type is single pole double throw (SPDT) with contacts rated
at 125 VAC/30 VDC with a maximum switched current of 5A.
The Digital Input in the Digital I/O communications provides MAX300
™
-LG with the
ability to monitor digital input signals that conform to the “IEC 61131-2, type 1”
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