A Modbus/Tcp Interface - Honeywell Midas S2 User Manual

Fixed single-point extractive gas transmitter

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6.8 A Modbus/TCP Interface

The Midas S2 gas detector can report concentration information in a variety of formats

including relay contact closure, an analog 4-20 mA loop, Ethernet/ IP/HTML web pages and

via the Modbus/TCP networking protocol. This section defines the format of data in

Modbus/TCP registers. More information about Modbus/TCP can be obtained from www.

modbus.org.

The Midas S2 is a Modbus/TCP "server" as defined in the MODBUS Application Protocol

Specification V1.0 . It supports command 03 ("read holding registers") for registers 40001 to

40122 as listed in the following table.

The Midas S2 reports floating-point concentration numbers in little-endian or Intel format. This

is scaled in units of ppm for gasses which have display units of ppm or ppb. For other display

units the concentration is scaled directly in display units. This applies to registers Gas

Concentration and Alarm Threshold.

The Midas S2 fills 122 Modbus/TCP holding registers as listed in the following table. The

Monitoring Status register is a concise summary of Midas S2 status. The other registers provide

more complete information.

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