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H-424ms – Xylem H-424MS V1.0 User Manual

Page 20

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2-4 SDI-12 Command and Response Protocol

H-424MS

Example of a H-424MS "aV!" command:

Command

Response

Time Values

Description

-------------

---------------------

------- --------

---------------------------

"aV!"

"a0013"

1 sec 3

Return fixed data and diagnostic

data for testing purposes.

Subsequent Command

Response

---------------------------

--------------------------------------------

"aD0"

a+123.456+78.9+y

Key

Description

Units

-------------

-------------------------

----------------------------

+123.456

Fixed test data

+78.9

Fixed test data

y

ROM checksum test

0 = Failed, 1 = Passed

2.4 Initiate Verify Command

The Verify Command causes a verify sequence to be performed. The result of this command is

similar to the "aM!" command except that the values generated are fixed test data and the results of

diagnostic checksum tests. The data generated in response to this command is placed in the sensor's

buffer for subsequent collection using "D" commands. The data will be retained in the sensor until

another “M”, “C” or “V” command is executed.

Command

Response

Description

-------------

-------------------------

---------------------------

"aV!"

"atttn"

Initiate verify sequence

Where:

a

is the sensor address ("0-9", "A-Z", "a-z", "*", "?").

V

is an upper-case ASCII character.

ttt

is a three digit integer (000-999) specifying the maximum time, in seconds,

the sensor will take to complete the command and have data available in its

buffer.

n

is a single digit integer (0-9) specifying the number of values that will be

placed in the data buffer. If "n" is zero (0), no data will be available using

subsequent "D" commands