ST100A Series Flow Meter OPERATION
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in the Modbus standard integer register form. And lastly registers 4111, 4112, 4113, and 4114 offer the flow totalizer as a single precision
floating point value in the Modbus standard register form. Because the Totalizer values can become a very large number, the single
precision floating point presents the data as two register groups. Group 1 called TOTALIZER 1 holds the lower count with a defaulted
count limit of 65,535.996. TOTALIZER 1 resets back to zero when the count limit is reached. Group 2 called TOTALIZER 2 holds the upper
count and it increments by 1 every time the group 1 registers reach the 65,535.996 count or the set “Totalizer Max Limit” count.
TOTALIZER 2 has a maximum count of 4,294,967,295, after which it resets back to zero.
The TOTALIZER 1 group maximum count value can be set to a lower value of the default value by the user. This is controlled by service
registers 4115 and 4116 for which values above 65,535.996 are not permitted. The default value of 65,535.996 for TOTALIZER 1 provides
a resolution 0.01 to the ST100A Series Totalizer value.
To r
econstruct the double precision floating point value of the Totalizer using the single precision floating point registers do the following:
(
)
= 2
×
1
+
1
Table 21 – ST100A Series Modbus Process Data
Variable/Parameter
Register
Data Type
1
Access
2
2
2
2
2
2
Totalizer Eng. Units Code
Device (Sensor 1) Status Code #1
Device (Sensor 1) Status Code #2
Notes: 1. Data Type: Special1 is a collection of discrete registers that contain a single precision (32-bit) floating point
value, and must be treated and interpreted as a single precision floating point number by the DCS or the PLC.
Special2 is a collection of discrete registers that contain a double precision (64-bit) floating point value, and
must be treated and interpreted as a double precision floating point number by the DCS or the PLC.
2. (D) indicates double precision (64 bits).
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