Trolex AirXD Modbus Addresses

Modified on Thu, 21 Mar at 5:46 PM

The AIR XD contains the following three MODBUS registers:

Input Registers - FC04

This is a read-only register containing factory programmed instrument parameters, including serial numbers, firmware versions and live data sets.

Register	Description	Data Type	Units
0	Product TX number	Uint16_t
1	Firmware Version (major)	Uint16_t
2	Firmware Version (minor)	Uint16_t
3	Firmware Version (patch)	Uint16_t
4	Serial number (characters 1 & 2)	Char	Ascii format
5	Serial number (characters 3 & 4)	Char	Ascii format
6	Serial number (characters 5 & 6)	Char	Ascii format
7	Serial number (characters 7 & 8)	Char	Ascii format
8	Serial number (characters 9 & 10)	Char	Ascii format
9	Bin 0 to 0.46 μm	Uint16_t	Counts
10	Bin 1 to 0.66 μm	Uint16_t	Counts
11	Bin 2 to 0.89 μm	Uint16_t	Counts
12	Bin 3 to 1.17 μm	Uint16_t	Counts
13	Bin 4 to 1.47 μm	Uint16_t	Counts
14	Bin 5 to 1.80 μm	Uint16_t	Counts
15	Bin 6 to 2.5 μm	Uint16_t	Counts
16	Bin 7 to 3.5 μm	Uint16_t	Counts
17	Bin 8 to 4.51 μm	Uint16_t	Counts
18	Bin 9 to 5.76 μm	Uint16_t	Counts
19	Bin 10 to 7.25 μm	Uint16_t	Counts
20	Bin 11 to 9 μm	Uint16_t	Counts
21	Bin 12 to 11 μm	Uint16_t	Counts
22	Bin 13 to 13 μm	Uint16_t	Counts
23	Bin 14 to 15.01 μm	Uint16_t	Counts
24	Bin 15 to 17.01 μm	Uint16_t	Counts
25	Bin 16 to 19.02 μm	Uint16_t	Counts
26	Bin 17 to 21.02 μm	Uint16_t	Counts
27	Bin 18 to 25.76 μm	Uint16_t	Counts
28	Bin 19 to 26.51 μm	Uint16_t	Counts
29	Bin 20 to 29.51 μm	Uint16_t	Counts
30	Bin 21 to 32.51 μm	Uint16_t	Counts
31	Bin 22 to 35.51 μm	Uint16_t	Counts
32	Bin 23 to 38.51 μm (140μg/m extended)	Uint16_t	Counts
33	Sampling period	Uint16_t	Counts
34	Sample flow rate	Uint16_t	0.01 ml/s/bit
35	Sensor temperature	Uint16_t	0.01°C/bit
36	Sensor humidity	Uint16_t	0.01%/bit
37	PM A size (lower 16 bits)	Float32_t	μg/m^3
38	PM A size (upper 16 bits)	Float32_t	μg/m^3
39	PM B size (lower 16 bits)	Float32_t	μg/m^3
40	PM B size (upper 16 bits)	Float32_t	μg/m^3
41	PM C size (lower 16 bits)	Float32_t	μg/m^3
42	PM C size (upper 16 bits)	Float32_t	μg/m^3
43	PM D size (lower 16 bits)	Float32_t	μg/m^3
44	PM D size (upper 16 bits)	Float32_t	μg/m^3
45	TSP (lower 16 bits)	Float32_t	μg/m^3
46	TSP (upper 16 bits)	Float32_t	μg/m^3
47	PM A "Average 1" (lower 16 bits)	Float32_t	μg/m^3
48	PM A "Average 1" (upper 16 bits)	Float32_t	μg/m^3
49	PM B "Average 1" (lower 16 bits)	Float32_t	μg/m^3
50	PM B "Average 1" (upper 16 bits)	Float32_t	μg/m^3
51	PM C "Average 1" (lower 16 bits)	Float32_t	μg/m^3
52	PM C "Average 1" (upper 16 bits)	Float32_t	μg/m^3
53	PM D "Average 1" (lower 16 bits)	Float32_t	μg/m^3
54	PM D "Average 1" (upper 16 bits)	Float32_t	μg/m^3
55	TSP "Average 1" (lower 16 bits)	Float32_t	μg/m^3
56	TSP "Average 1" (upper 16 bits)	Float32_t	μg/m^3
57	PM A "Average 2" (lower 16 bits)	Float32_t	μg/m^3
58	PM A "Average 2" (upper 16 bits)	Float32_t	μg/m^3
59	PM B "Average 2" (lower 16 bits)	Float32_t	μg/m^3
60	PM B "Average 2" (upper 16 bits)	Float32_t	μg/m^3
61	PM C "Average 2" (lower 16 bits)	Float32_t	μg/m^3
62	PM C "Average 2" (upper 16 bits)	Float32_t	μg/m^3
63	PM D "Average 2" (lower 16 bits)	Float32_t	μg/m^3
64	PM D "Average 2" (upper 16 bits)	Float32_t	μg/m^3
65	TSP "Average 2" (lower 16 bits)	Float32_t	μg/m^3
66	TSP "Average 2" (upper 16 bits)	Float32_t	μg/m^3
67	Air XD supply voltage	Uint16_t	mv/bit
68	Laser current / mA	Uint16_t	mv/bit
69	Fan current / mA	Uint16_t	mv/bit
70	Status register	Uint16_t

Coil Registers - FC1, FC5

This is a read/write register containing the instrument binary settings, including alarm status,

PM units and 4 - 20 mA output “Enable”/“Disable” status.

Writing to this register will result in the setting being changed permanently. However, if an alarm is activated, writing to the alarm status coil will dismiss the active alarm until the alarm threshold parameters have been re-exceeded.

Register	Description	Data Type	Units
0	"Channel 1" alarm status	Bool
1	"Channel 2" alarm status	Bool
2	"Channel 1" alarm latch	Bool	0: Auto-reset 1: Latch
3	"Channel 2" alarm latch	Bool	0: Auto-reset 1: Latch
4	"Channel 1" alarm mute	Bool
5	"Channel 2" alarm mute	Bool
6	PM units	Bool	0: μg/m^3 1: mg/m^3
7	Reserved for future use	Bool
8	Memory module fitted	Bool	0: Not fitted 1: Fitted
9	4-20 mA "Channel 1" Enable/Disable	Bool	0: Disabled 1: Enabled
10	4-20 mA "Channel 2" Enable/Disable	Bool	0: Disabled 1: Enabled
11	Top cap status (read only)	Bool	0: Disabled 1: Enabled
12	Alarm "Channel 1" Enable/Disable	Bool	0: Disabled 1: Enabled
13	Alarm "Channel 2" Enable/Disable	Bool	0: Disabled 1: Enabled
14	Relay 1 override	Bool	0: Relay under alarm control 1: Relay override active
15	Relay 2 override	Bool	0: Relay under alarm control 1: Relay override active
16	Floating point data endianness	Bool	0: Big Endian 1: Little Endian
17	Floating point data byte swap	Bool	0: No byte swap 1: Byte swap enabled

Holding Registers - FC3, FC6

This is a read/write register containing the instrument settings and parameters, including instrument date, time, PM assignment and MODBUS settings. Writing to this register will result in the setting being changed permanently.

Note: Writing to the MODBUS settings will result in communication errors until the user has changed their local instrument MODBUS parameters to match the new setting selected on the AIR XD.

Register	Description	Data Type	Units
0	Time (seconds)	Uint16_t
1	Time (minutes)	Uint16_t
2	Time (hours)	Uint16_t
3	Date (day)	Uint16_t
4	Date (month)	Uint16_t
5	Date (year)	Uint16_t
6	UTC offset (minutes)	Uint16_t
7	UTC offset (hours)	Uint16_t
8	PM A assignment	Uint16_t	x100
9	PM B assignment	Uint16_t	x100
10	PM C assignment	Uint16_t	x100
11	PM D assignment	Uint16_t	x100
12	Alarm 1 assignment	Uint16_t	0: PM A live 1: PM B live 2: PM C live 3: PM D live 4: TSP live 5: PM A Avg 1 6: PM B Avg 1 7: PM C Avg 1 8: PM D Avg 1 9: TSP Avg 1 10: PM A Avg 2 11: PM B Avg 2 12: PM C Avg 2 13: PM D Avg 2 14: TSP Avg 2
13	Alarm 2 assignment	Uint16_t	0: PM A live 1: PM B live 2: PM C live 3: PM D live 4: TSP live 5: PM A Avg 1 6: PM B Avg 1 7: PM C Avg 1 8: PM D Avg 1 9: TSP Avg 1 10: PM A Avg 2 11: PM B Avg 2 12: PM C Avg 2 13: PM D Avg 2 14: TSP Avg 2
14	Alarm 1 threshold	Uint16_t	As μg/m^3
15	Alarm 2 threshold	Uint16_t	As μg/m^3
16	4-20mA "Channel 1" assignment	Uint16_t	0: PM A 1: PM B 2: PM C 3: PM D
17	4-20mA "Channel 2" assignment	Uint16_t	0: PM A 1: PM B 2: PM C 3: PM D
18	4-20mA "Channel 1" scaling	Uint16_t
19	4-20mA "Channel 2" scaling	Uint16_t
20	Average "Channel 1" time	Uint16_t	As minutes
21	Average "Channel 2" time	Uint16_t	As minutes
22	Baud rate	Uint16_t	0: 4800 1: 9600 2: 14400 3: 19200 4: 38400 5: 57600 6: 115200
23	Modbus Address	Uint8_t

Reading floating point registers

MODBUS itself does not define a floating point data type but it is industry standard to use the IEEE-754 standard for defining floating point numbers. There is, however, there is no clear-cut definition of the byte order of the data payload.

By default, the Trolex AIR XD uses a little-endian format for the floating point numbers split across two 16-bit MODBUS registers. If this is not compatible with your system and a big endian format or byte swapping is required, the byte ordering can be switched using the on-device menus.