YSI 6500 Environmental Process Monitor - Manual (Page 49)

Proper Use and Care of the 6500
Section 5
641-655 Read only Scaled integer parameter data
The PLC should only read data from the 6500 using this
method if it cannot handle floating point data. Most PLCs
can manipulate floating point values, so you should try to
avoid reading scaled integer values. The value in register 641
corresponds to the parameter type in register 129 and so on.
The values are scaled according to a fixed table in the 6500.
The scaled data is in an unsigned integer format. Each
parameter type has a specific range and resolution. Refer to
the scaled integer range table for values for each parameter.
For example temp C has the range of –50 to 605.35, with a
resolution of 0.01. Here’s some integer values that could be
returned and their engineering equivalents:
0: -50 C or less.
1: -49.99 C
2: -49.98 C
5000: 0 C
7234: 22.34 C
7500: 25 C
65534: 605.34 C
65535: 605.35 C or higher
656-and
up Unused
MODBUS BASE ADDRESS
The 6500 is designed to allow multiple sondes to be connected at the same time. Each sonde has
its own address that must be different from each other. For example you could connect 4 sondes
at the same time with address 0, 1, 2, and 3. These addresses will be displayed on the 6500’s
screen during normal operation. In order for the PLC to access data from each of the sondes, the
6500 system consumes 1 Modbus address for each of the sondes. The effective address is
computed by adding the sonde address to the address that you assigned in the Modbus Setup
menu. Continuing with the previous example, if you set the 6500’s Modbus address to 10, then
the 4 sondes would be accessed at Modbus addresses 10, 11, 12, and 13. Note that if you have
only 1 sonde connected to the 6500, you will still need to know what the sonde’s address is in
order to access the data. To force the sonde address to be displayed on the screen, go to the
“Main” menu, then “Display” and enable the item “Multi sonde”. When you exit to the normal
display you will see the heading “Sonde:X” where “X” will be the sonde address.
Note that the 6500 “consumes” 10 contiguous Modbus address starting from what you defined for
the base address. This is true even if no sondes are on line. Therefore if you have more then one
6500 connected to the same Modbus port make sure the base address on each differ by at least 10.
For example, if the base address on one 6500 is 1 then you could set the base address on another
6500 to 11 and yet a third 6500 to 21. A good scheme would be to use bases addresses like 10,
20, 30, etc.
YSI Incorporated 6500 Environmental Process Monitor 46