Manipulated Variable Processing, Outputs-Heating Switch - Siemens SIMATIC S5 Manual

Description of the Firmware
To obtain a temperature related to 0 C, the reference junction is acquired as
U = K T and is included in U
TH 2 2
The temperature compensation is performed via a Pt 100 resistance thermometer with which the
reference junction temperature is read in at the beginning of each cycle. The Pt 100 at channel 15
is also checked for line break. If a line break or a temperature > 60 C is detected, an error bit is
set (message 16, byte 2). In this case, the value of the ambient temperature before the error was
detected is used for further calculation. If the error occurs immediately after parameter assignment,
the ambient temperature 0 C (= 32 F) is used.
To indicate the actual value, a filter can be looped into the signal path. If this is required, appropriate
parameters must be assigned. The actual value is displayed with a time delay after averaging eight
values.
If more than 1024 or 2048 encoding units (or 3997 encoding units in pure Pt 100 operation and 1536
encoding units with the special function) are read in, the actual value is limited to the maximum
value. The actual values can be represented either as binary or BCD coded values as required. The
actual values are stored in message 17.
If BCD coding is required, the values are stored as follows:
S5 format
Address n:
Address n + 1:

1.1.3 Manipulated Variable Processing, Outputs-Heating Switch

The module has 17 digital control outputs for the 13 controllers. This means that nine 2-step
controllers and four 3-step controllers or a maximum of eight 3-step controllers and one 2-step
controller can be configured (control byte 1).
Depending on the configuration, the outputs of 2 or 3-step controllers are assigned to the inputs
internally by the firmware. If, for example, three controllers are configured as 2-step controllers with
input channels 0, 1 and 2, the manipulated variables are output at outputs 17, 16 and 15
respectively. If a 3-step controller is configured as the fourth controller with input channel 3, the
manipulated variable (e.g. heating, cooling) will then be output at outputs 14 and 13.
The manipulated variable calculated from the control algorithm forms a 2 or 3-step signal depending
on the configuration. With the pulse-duration modulation (percentage output), the manipulated
variable (heating or cooling) is only output for the part of the sampling time (T
to the calculated value of the controller output signal. The smallest ON interval is 50, 55, 60 or 80 ms
depending on the parameter assignment (see Operating Instructions in this manual, Section 3.4.2).
At a sampling time of 10 s, for example, a resolution of maximum 0.5% is achieved at an ON interval
of 50 ms. To suppress short ON or OFF times, a response threshold can also be input.
4–8
.
Th
thousands hundreds
tens units
) which corresponds
A
IP244
C79000–B8576–C860–02