Detcon FP-624C Manuel d'utilisateur télécharger pdf (Page 21)

Fail-Safe/Fault Supervision

Model FP-624C MicroSafe™ sensors are programmed for fail-safe operation. Any of the following fault condition

will activate the fault relay, illuminate the fault LED, and cause the display to read its corresponding fault condi-

tion: “SENSOR FAULT”, “SIGNAL FAULT”, “HEATER FAULT”, or “CAL FAULT”. A “Sensor Fault”,

“Signal Fault”, and “Heater Fault”, will also cause the mA output to drop to zero (0) mA.

Sensor Life

The sensor life feature is a reference based on signal output from the sensor cell. When a sensor life of 25% or less

remains, the sensor cell should be replaced within a reasonable maintenance schedule.

3.12 RS-485 PROTOCOL

Detcon MicroSafe™ sensors feature Modbus™ compatible communications protocol and are addressable via rotary

dip switches for multi-point communications. Other protocols are available. Contact the Detcon factory for specific

protocol requirements. Communication is two wire, half duplex 485, 9600 baud, 8 data bits, 1 stop bit, no parity,

with the sensor set up as a slave device. A master controller up to 4000 feet away can theoretically poll up to 256

different sensors. This number may not be realistic in harsh environments where noise and/or wiring conditions

would make it impractical to place so many devices on the same pair of wires. If a multi-point system is being uti-

lized, each sensor should be set for a different address. Typical address settings are: 01, 02, 03, 04, 05, 06, 07, 08, 09,

0A, 0B, 0C, 0D, 0E, 0F, 10, 11, etc.

In most instances, RS-485 ID numbers are factory set or set during installation before commissioning. If required,

the RS-485 ID number can be set via rotary dip switches located on the preamp circuit board. However, any change

to the RS-485 ID number would require the sensor housing to be opened, thus declassification of the area would

be required. See section 3.5.4-f for details on changing the RS-485 ID number.

The following section explains the details of the Modbus™ protocol that the MicroSafe™ sensor supports.

Code 03 - Read Holding Registers, is the only code supported by the transmitter. Each transmitter contains 6 hold-

ing registers which reflect its current status.

High Byte Low Byte

40000 Gas type Sensor Life

Gas type is one of the following:

01=CO, 02=H2S, 03=SO2, 04=H2, 05=HCN, 06=CL2, 07=NO2, 08=NO, 09=HCL, 10=NH3, 11=LEL, 12=O2

Sensor life is an estimated remaining use of the sensor head, between 0% and 100%

Example: 85=85% sensor life

High Byte Low Byte

40001 Detectable Range

i.e. 100 for 0-100 ppm, 50 for 0-50% LEL, etc.

High Byte Low Byte

40002 Current Gas Reading

The current gas reading as a whole number. If the reading is displayed as 23.5 on the display, this register would

contain the number 235.

High Byte Low Byte

40003 Alarm 1 Setpoint

Model FP-624C Combustible Gas Sensor PG.21

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Detcon FP-624C Manuel d'utilisateur Page 21