Detcon PI-600 - Manual (Page 35)

Reg40004 Data Hi 00 0 0000 0000
Reg40004 Data Lo 14 20 0001 0100
Reg40005 Data Hi 05 5 0000 0101
Reg40005 Data Lo 50 80 0101 0000
CRC ## #### ####
CRC ## #### ####
Additional Notes:
The calibration LED will light when the transmitter is sending a response to a Master Query.
Communications are 9600 baud, 8 data bits, 1 stop bit, No parity, half duplex 485.
On ranges set from 1 ppm to 10 ppm the reading and alarm set points are displayed as ##.##ppm.
On ranges set from 15 ppm to 50 ppm the reading and alarm set points are displayed as ##.#ppm.
To accommodate these fractional readings using the Modbus™ interface, the reading and alarm set points are multi-
plied by 100 before they are stored for retrieval by a Modbus™ command.
Examples:
The transmitter is set for a range of 5 ppm.
The display on the transmitter reads 2.74 ppm.
The transmitter is polled for its reading using a Modbus™ command.
The value returned in the response is decimal 274.
Obtain the correct reading by dividing.
274/100 = 2.74 ppm.
The transmitter is set for a range of 25 ppm.
The display on the transmitter reads 22.9 ppm.
The transmitter is polled for its reading using a Modbus™ command.
The value returned in the response is decimal 2290.
Obtain the correct reading by dividing.
2290/100 = 22.9 ppm.
On ranges above 50 ppm there is no math involved. The readings are stored the same as they are seen on the transmit-
ters display.
3.15 T
ROUBLE
S
HOOTING
Sensor reads Over-range after Power-up
Probable Cause: Sensor requiring additional stabilization time, VOC gases present in background air, Improper zero or
span calibration.
1. Verify that there is not large amounts of target gas or interfering gases in background.
2. Redo zero and span calibrations.
3. Make sure transmitter range is consistent with PID sensor head range.
Reading Higher than Anticipated
Probable Causes: Target or Interfering gases in background, Incorrect calibration for Zero or Span.
1. Verify no target or interfering gases are present. If so, use the Zero Offset feature.
2. Redo Zero and Span calibrations with validated Zero Gas and Span Gas standards.
Reading Lower than Anticipated
Probable Causes: Zero Calibration done before unit f inished stabilizing, Incorrect Span Calibration.
1. Redo Zero and Span calibrations with validated Zero Gas and Span Gas standards.
2. Disengage Zero Offset feature if it is not necessary.
3. Contact Detcon to determine if target gas will not diffuse past the 316 Stainless Steel f lame arrestor.
Zero Calibration Fault
Probable Causes: Target gas or Interfering gases in background during Zero Calibration, Failed PID sensor.
PI-600 Toxic Gas Sensors PG.35