LS A2C-SG2-M12, Руководство пользователя

Страница: 35 / 44

A2C-SG2-M12
WWW.LILLIESYSTEMS.COM
35 of 44
13.2.2
Command: Get Periodic Messages to follow ADC - J1939 style
Send this command:
Command Sub Command Data[0] Data[1] Data[2] Data[3] Data[4] Data[5]
0x6F
DLC = 0x01 (values above 0x01 are also valid, but Data bytes are not used)
Reply:
Command Sub Command Data[0] Data[1] Data[2] Data[3] Data[4] Data[5]
0x6F VAL
DLC = 0x02
VAL returns 0x00 / 0x01 / 0x02 - as described for the Set command 0x6E
14 Signal to Noise calculations
The A2C-SG2 can be setup to output the SNR (signal to noise ratio) continuous in order to check the system for interference or
noise. The output is calibrated in dB comparing the sampled data to the full swing of the ADC input voltage.
To evaluate the performance of the setup, the strain gauges must be held in a steady state. Alternatively, the input may be shorted
at the gauge.
Both channels will be computed when the SNR is enabled. It is not possible to only enable one channel.
To setup SNR messages the number of samples must be specified. The value depends on the rate of SNR measurements required
and on the data rate. If the data rate i.e. is set to 300 Hz, and the number of SNR measurements is set to 300, then the SNR will be
outputted every second. The peak minimum and maximum values of those 300 samples are used to calculated the SNR.
To turn off the SNR calculations send 0 as the number of samples.
14.1.1 Command: Set SNR sample numbers
Command Sub Command Data[0] Data[1] Data[2] Data[3] Data[4] Data[5]
0x48 RESV Data MSB Data LSB
DLC = 0x04 (values above 0x04 are also valid, but Data bytes are not used)

RESV: Reserved for future use

Data:
16b unsigned integer containing the number of samples
When the SNR calculations are ready the A2C-SG2 will send the following message with the result which is identical to a standard
message (value type mean):
Reply:
Command Sub Command Data[0] Data[1] Data[2] Data[3] Data[4] Data[5]
0x0B Channel 0x01 0x04 Data MSB Data Data Data LSB
DLC = 0x04
Channel: is the channel number that is requested and must be one of the following values

0x00 = channel 1

0x01 = channel 2
Data:
32b float type, big endianness.
From the A2C-Sensor Utility you can directly enable the SNR function. Under the Digital Filters tap, set the Samples and click “Start
SNR measurements”