Analog Adjustments - Siemens SIMATIC S7-200 System Manual

6.7

Analog Adjustments

The analog adjustment potentiometers are located under the front access cover of
the module. You can adjust these potentiometers to increase or decrease values
that are stored in bytes of Special Memory (SMB28 and SMB29). These read-only
values can be used by the program for a variety of functions, such as updating the
current value for a timer or a counter, entering or changing the preset values, or
setting limits.
SMB28 holds the digital value that represents the position of analog adjustment 0.
SMB29 holds the digital value that represents the position of analog adjustment 1.
The analog adjustment has a nominal range of 0 to 255 and a repeatability of
counts.
You use a small screwdriver to make the adjustments: turn the potentiometer
clockwise (to the right) to increase the value, and counterclockwise (to the left) to
decrease the value. Figure 6-10 shows an example program using the analog
adjustment.
I0.0
SMB28
Q0.0
/
VW100
T33
Figure 6-10
S7-200 Programmable Controller System Manual
A5E00066097-02
LAD
B_I
Read analog
EN ENO
adjustment 0
and save the
word-based
IN OUT VW100
value in VW100.
T33
Use the word-based
TON
IN
value as a preset
for a timer. Turn on
Q0.0 when T33
PT
reaches preset.
Q0.0
Example of Analog Adjustment
CPU and Input/Output Configuration
STL
LD I0.0
BTI SMB28, VW100
LDN Q0.0
TON T33, VW100
LD T33
= Q0.0
2
6-13