Siemens SIMATIC S5 Manual page 153

Channel 13 is intended to monitor power supply voltage fluctuations.
With heating current monitoring, the heating current is monitored for 2 and 3-step controllers both
when it is on and off. Either solid state relays or contactors are permitted as the switching devices
for heating bands. Switching devices with switching times up to 50 ms can be used for hot channel
control. This means that when the heating current is on, currents can only be monitored when the
ON time per sampling period is at least 100 ms. The same applies for monitoring currents in the
OFF state.
For standard temperature control, switching devices with make times of maximum 100 ms,
maximum 150 ms or maximum 200 ms can be used (see Fig. 3.3.4/1). Using main control byte 3,
bits 6 and 7, you can inform the IP of the maximum make times of your switching devices. The break
times of the switching devices must be a maximum of 50 ms.
Currents can only be measured in the ON state when the heating is switched on for at least 150 ms
(make time 100 ms) or 200 ms or 250 ms (for make times of 150 ms or 200 ms) during a sampling
period. To monitor currents in the off state, the OFF time per sampling period must be at least 100
ms.
For measuring the actual value of the currents and power supply voltage, a software filter minimizes
the influence of disturbances.
Fig. 3.3.4/2 Typical make times of contactors of different capacities
IP244
C79000–B8576–C860–02
Special Functions for Plastic Machines
4–87