Owner's manual

10
2.6 - Data Points
The data points available are:
Product – Position of top fl oat, in inches or centimeters.
Interface – Position of bottom fl oat.
Temperature – Fahrenheit or Celsius.
Average temperature – Covered product and interface.
Product temperature – Average temperature of product
only.
Interface temperature – Average temperature of inter-
face only.
Individual Temperature sensors – 5 total, 1 is closest
to the bottom of the probe, 5 is closest to the top.
Maximum temperature - Recorded by any of the sen-
sors, saved through power cycles.
Temperature sensor locations- 5 total, indicates sen-
sor location from bottom of tank.
2.7 - Error Codes
Value of 2000 in the product or temperature registers
indicates a loss of signal.
Value of 2000 in the interface register indicates a loss
of signal.
Value of 1000 in the product register indicates a com-
munication problem or “dead” probe.
Value of 1000 in the interface register indicates a com-
munication problem or “dead” probe.
Status Bit Defi nitions – Internal diagnostic indication
(see Chart)
2.8 - Scaling
All integer formats are scaled X 100 so that the last 2
digits represent the decimal portion of the number. For
example:
Product reading: 1790 = 17.90 inches
Interface reading: 563 = 5.63 inches
Average Temperature: 2382 = 23.82 degrees Celsius
2.9 - Holding and Input registers
All data points can be accessed as either a holding or
an input register. Holding registers start with a 3XXXX
and Input registers start with a 4XXXX. For example,
product can be obtained at both registers 30203 and
40203.
2.10 - Enron Modbus
Enron Modbus has a few differences from Traditional
Modbus. One difference is the register offsets follow
a different numbering scheme, with integer values
residing in the 3XXX range, long integers in the 5XXX
range, and fl oating points in the 7XXX range. The sec-
ond difference is that 32 bits of data can be returned
in one register. The 7231 HT supports both of these
features, by selection of the proper register value.
2.11 - Maximum registers
The maximum number of registers that can be ac-
cessed in a single Modbus request depends on the
mode (RTU or ASCII) and the register size of the data
(i.e Enron uses 4 data bytes per register for fl oats and
longs)
1) For ASCII setting , accessing Enron fl oats or long
integers, the maximum number of registers that can
be requested is 30.
2) For all other modes, the maximum number is 36,
which will retrieve all the data points in a single
message.
2.12 - Examples of Accessing Data in
the 7231 HT
For the following examples, suppose we have
these values:
Product (level) reading: 200.74 inches, 509.88 cm
Interface reading: 120.39 inches, 305.79 cm
Average Temperature: 26.94 degrees C, 80.49 F
1) To access Product as an integer, Big Endian order,
in inches: Request register 31803, length 1, value
returned = 20074
2) To access Interface as a Floating Point, Little
Endian order, in cm :Request register 30905, length
2, value returned = 305.79
3) To access Avg Temperature as a long integer, Big
Endian Byte Swapped, in C: Request register
31511, length 2, value returned = 2694
4) To access product as an integer, Big Endian, in
Enron addressing, in inches: Request register
3002, length 1, value returned = 20074
5) To access Interface as a Floating Point, Big Endian,
in Enron addressing, in cm: Request register 7104,
length 1, value returned = 305.79
6) To access Avg Temperature as a long integer, Little
Endian in Enron addressing, in F: Request register
5610, length 1, value returned = 8049
7) To access all of the data points in Floating point, Big
Endian, English units: Request register 30203,
length 36