Oldham iTrans, User Manual, Page: 56 / 88

ModBus Interface iTrans Fixed Point Single/Dual Gas Monitor
6-2 iTrans User Manual (P/N: 77023554-1)
Example: Gas reading of 5 ppm = register value of $0005.
Example: Gas reading of 20.9% = register value of $0209.
For Channel 2 you can access the gas reading by looking at register 40202.
For a full list of ModBus commands and registers that are accessible on the
, refer to the next section or, for the most up-to-date list, contact the
Technical Support group of Oldham at 1-713-559-9280.
6.3. ModBus Register List
ModBus register addresses are provided in Table 6-2.
Table 6-2. ModBus Registers
Addr
Inst
R/W
Host
R/W
Range Description
40101 R/W R/W MSB = $01 to $FF
LSB = $01 to $F7
Sensor Type
Holds the sensor instrument type code and
ModBus address. The most significant byte
(MSB) holds a value indicating the type of
instrument (see below). The least significant
byte (LSB) holds a value which is the ModBus
address of the sensor.
MSB = Instrument type code $01 to $FF
$03 = BBIR (broad band infrared)
$04 = TOX (toxic)
$05 = OXY (oxygen)
$06 = AAW (toxic)
$07 = CAT (catalytic)
LSB = MODBUS sensor address $01 to $F7
(1 to 247)
40102 W R $0000 to $FFFF Gas Reading
Holds the gas reading in ppm or percent
depending upon the sensor in the instrument.
The range is from $0000 to $FFFF and
represents a signed decimal value range
from -32768 to +32767.
Examples:
+5 ppm = register value of 00005
10
= $0005
-5 ppm = register value of 65531
10
= $FFFB