ECM NH3CAN, Инструкция по эксплуатации, Страница: 15 / 35

15
8.0 Commands to the NH
3
CAN Module
There are several commands that can be used with the NH
3
CAN module. The commands are
executed by performing an SDO Write to OD address 0x1023, subindex 0x01. A list of the
commands can be found in Appendix B.
8.1 ZEROing and SPANing
All calibration information, including sensor constants and the user-performed span, is stored in
a memory chip located in the connector of the NH
3
sensor. The NH
3
value does not depend on
what module the sensor is plugged into, they depend on the factory calibration and user zero and
span information stored in the sensor’s connector that is attached to the sensor.
To compensate for sensor aging, the NH
3
sensor can be recalibrated. To perform a recalibration
of the NH
3
measurement, three messages must be sent to the NH
3
CAN. The procedure is as
follows:
i) SDO Write to OD address 0x5000 of the current NH
3
value output by the module.
ii) SDO Write to OD address 0x5001 of the true/correct NH
3
value.
iii) OS Command to ZERO/SPAN NH
3
.
The first message contains the NH
3
CAN output for NH
3
. Bytes 4-7 contain a single precision
32bit floating point value that conforms to the IEEE-754 standard. It is loaded least significant
byte first (Intel format).
CANid byte 0 byte 1 byte 2 byte 3 byte 4 byte 5 byte 6 byte 7
0x600+NID 0x23 0x00 0x50 0x00 value output by NH
3
CAN (float)
The second message contains the true value of NH
3
.
CANid byte 0 byte 1 byte 2 byte 3 byte 4 byte 5 byte 6 byte 7
0x600+NID 0x23 0x01 0x50 0x00 true value (float)
The third message sent is the OS Command to ZERO NH
3,
or SPAN NH
3
.
To ZERO NH
3
send:
CANid byte 0 byte 1 byte 2 byte 3 byte 4 byte 5 byte 6 byte 7
0x600+NID 0x2F 0x23 0x10 0x01 0x0F
To SPAN NH
3
send:
CANid byte 0 byte 1 byte 2 byte 3 byte 4 byte 5 byte 6 byte 7
0x600+NID 0x2F 0x23 0x10 0x01 0x10