Vaisala WINDCAP WS425 User's Guide download pdf (Page 179)

Chapter 5 _________________________________________________________________ Operation

WS425 A/B SDI-12 Message for V Command

When you have given the commands aV! and aD0!, the response

is the following:

a<watchdog><WS_unit><SDI-mode><spare><CR><LF>

where

Single-digit WMT700 address that corresponds to the

first character of the address value

Number of times the watchdog has triggered. Ideally

should be zero. Format: +(c)c

<WS_unit>

Wind speed unit. The options are:

+0 = mph

+1 = kt

+2 = km/h

+3 = m/s

<SDI-mode>

Current sub mode setting. The options are:

+0 = SDI

-12 sub mode A

+1 = SDI

-12 sub mode B

<spare>

1 digit for factory use, format: +c

Terminates the response

The above are verification data fields.

Requesting Cyclic Redundancy Check

Error detection capability can be enhanced by using the aCC! or

aMC! command to start the measurement. These commands have

the same function and send the same response as commands aC!

and aM! respectively. The difference is that Cyclic Redundancy

Check will be appended to the data returned by aD0! command.

The 16-bit Cyclic Redundancy Check value is appended to the

response of aD0! command before the <CR><LF>. It is encoded

as three ASCII characters using the following algorithm:

1st character=0x40 OR (CRC shifted right 12 bits)

2nd character=0x40 OR ((CRC shifted right 6 bits) AND

0x3F)

3rd character=0x40 OR (CRC AND 0x3F)

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Vaisala WINDCAP WS425 User's Guide Page 179