Connecting to Generators

Connecting generators to Critical Labs is a bit more challenging than many other devices because most generators do not speak SNMP or Modbus Natively.

The three most common methods for connecting a generator to Critical Labs is Modbus TCP, Modbus RTU 485, and contact closure.

Modbus TCP

Modbus TCP is the newest and easiest method to connect a generator to Critical Labs. Modbus TCP provides the most comprehensive list of sensor information. Modbus TCP displays detailed information such as volts, KW, oil pressure, and coolant temp. Refer to your generator installation manual to see if your controller supports Modbus TCP.

Modbus RTU 485

Modbus RTU 485  displays similar information to Modbus TCP, the technology is older and slower than Modbus TCP. Modbus RTU 485 requires a Modbus RTU 485 to Modbus TCP converter.

Contact Closures

If the generator controller does not support Modbus TCP or Modbus RTU 485, contact closure may be a good option. Most generator controllers will support “Generator Running”, and “Common Alarm” via contact closure. Review the generator installation manual to see a full list of supported contact closures. 

Modbus TCP Modbus RTU 485 Contact Closure
Easy connection, only one Cat 5/6 Ethernet cable to generator controller from customers Ethernet network

       X

Generator interface needs to support Modbus TCP

       X

Fast speed 10/100

       X

Displays detailed sensor information from the generator, volts, KW, amps, oil pressure, and more

       X

       X

Requires Modbus RTU 485 to Modbus TCP conversion hardware

       

       X

Requires I/O controller hardware that converts contact closure to SNMP

       X

External power needed for powering conversion hardware

       X

       X

Additional cable needed, Shielded twisted pair cable between generator and conversion box

       X

One pair of tested pair cable is needed for each contact closure from the generator

       X

The generator must support Modbus RTU interface

       X

The generator must support contact closure, minimum "On Gen" and "Common Alarm"

       X

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