Instruction manual

MODBUS System Set Up
025-9209 33
An illegal data address exception will be returned to queries beginning at unused addresses,
40005 - 41010, 41088 - 42010, and 42167 - 99999.
Only one accumulator or counter can be polled at a time.
Table 17. Analog Accumulator Holding Register Addresses
Accumulator Value # Samples Sample Rate
1 41011 - 41013 41014 - 41016 41017
2 41021 - 41023 41024 - 41026 41027
3 41031 - 41033 41034 - 41036 41037
4 41041 - 41043 41044 - 41046 41047
5 41051 - 41053 41054 - 41056 41057
6 41061 - 41063 41064 - 41066 41067
7 41071 - 41073 41074 - 41076 41077
8 41081 - 41083 41084 - 41086 41087
Table 17 shows the MODBUS holding register addresses used for analog input accumulators.
The average value of the accumulator and the total accumulated value - scaled to real world
units - can be calculated with the formulas presented below. An example will follow to help
clarify things, but first, some definitions.
Values to be calculated are:
A = Average analog input value scaled to real world units.
T = Total accumulated value, scaled to real world units.
P = The time period, in seconds, that the accumulator has been running.
Values returned when the accumulator is read are:
V = Accumulator value, unscaled.
N = Accumulator number of samples.
R = Sample rate
Values that are dependent on the sensor being used are:
M
L
= lowest real world value measured by the sensor.
M
H
= highest real world value measured by the sensor.
S
L
= sensor output corresponding to ML - in Volts or mA.
S
H
= sensor output corresponding to MH - in Volts or mA.
I = analog input range - 5 Volts or 20mA depending on the type of sensor.
The formula for calculating the average analog input value in real world units is: