TF1100-CH transit-time handheld flowmeter manual
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6.4 PROTOCOL PREFIX USAGE
(1)
Prefix P
The prefix P can be added before any command in the above table to have the returning data
followed with two bytes of CRC check sum, which is the adding sum of the original
character string.
Take the DI+(CR) command as an example. Assume that DI+(CR) would return
+10m3(CR)(LF)( the string in hexadecimal is 2BH, 31H, 32H, 33H, 34H, 35H,
36H, 37H, 45H, 2BH, 30H, 6DH, 33H, 20H, 0DH, 0AH) , then PDI(CR) would return
+10m3!F7(CR)(LF). ‘!’ acts as the starter of check sum which is yielded by adding
up the string 2BH, 31H, 32H, 33H, 34H, 35H, 36H, 37H, 45H, 2BH, 30H, 6DH, 33H, 20H.
Please note that there will be SPACES (20H) before ‘!’.
(2)
Prefix W
The prefix W should be used in the network environment. The usage format is W + digit
string which stands for the IDN (Identification Number of the meter) + basic command.
The digit string should have a value between 0 and 65534 except 13(0DH), 10 (0AH),
42(2AH,*), 38(26H, &).
For example, if the IDN=254 instrument is addressed and returning the velocity of that
instrument is requested, the command will be W254DV(CR).
(3)
Prefix N
The prefix N is a single byte IDN network prefix, not recommended in a new design. It is
reserved only for the purpose of the compatibility with the former versions
(4)
Command Connector &
The & command connector can connect up to 6 basic commands to form a longer command
so that it will make the programming much easier.
For example, assume that the measurement of an instrument with DID=254 are going to be
returned, and (then) all the following 3 values--- (1) flow rate (2) velocity (3)POS
totalizer---will be returned simultaneously. The combined command would be
W254DQD&DV&DI+(CR), and the result would be:
+1.12m3/d(CR)
