Sensor Electronics SEC 3000, Instruction And Operation Manual

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SEC 3120 16-bit Modbus Manual Page 5 Of 46 Sensor Electronics Corporation
For Version 1.2 and above December 2012 P/N 1580282, Rev. 1, 20121228
Communication Parameters

Protocol: Modbus RTU slave.

Baud rates: 1200, 2400, 4800, 9600, 19200 bps field selectable, Word length 8.

Parity: Odd, Even, None, field selectable.

Stop Bits: 1 or 2, field selectable.

Electrical Interface:
o
RS 485, multi-drop 2-wire positive/negative (using A/B nomenclature).
o
Transmit and Receive: Half Duplex.
o
Useable speed will depend on cable length.

Modbus addressable: 1-247 (up to 254 if ONLY SEC 3120 units on a single bus).
Modbus Sensor Read Only Registers

Gas concentration (expressed as an integer scaled up by factor) representing the
units of measurement for that specific sensor’s current gas type (PPM, % LEL,
%V/V, etc.)

Operating Status (normal, calibrating, self test, start up, in an alarm (low, mid
high) or fault

Gas category Type (toxic, hydrocarbons, oxygen, etc.)

Sensor firmware version

Sensor serial number

Alarm relay mode (trip above or below threshold, audible or normal action)

Modbus address (Network ID)

Sensor Range and Gas Factor

Sensor Status and Error code, as well as Cell Test Warn code

ASCII Gas name and Gas Units Name
Modbus Sensor Read/Write Registers

Alarm thresholds (low, mid and high set points)

Zone ID (Network Zone ID)

Execute Self Test
Modbus 3120 Unit Read Only Registers

Unit Operation Status

Unit Fault Relay Reason Code

Unit Serial Number

Maximum Number of Sensors That Can Be Attached

Unit Clock- Read Current Time

Unit Type

Unit Firmware Version Info