Example: Heating A Liquid - Siemens SIMATIC ET 200S Operating Instructions Manual

5.4.3

Example: Heating a Liquid

Description
A liquid is heated with an electrical heating element. The energy needed to do this is
supplied to the heating element by a switching element (a contactor, for example).
The 2PULSE generates a 24 V control signal on its digital output for the switching element.
The temperature of the heating element is determined by the on/off length of the 24 V control
signal.
The longer the 24 V control signal is switched on, the longer the heating process and
therefore the greater the rise in temperature of the fluid.
Figure 5-19
Requirements
• The heating element only has two switching states: ON or OFF.
• The actual heating current corresponds to the ratio of the on/off duration of the 24 V
• The minimum pulse or minimum interpulse period must be greater than the response
Pulse-Width Modulation (PWM) Mode
Use channel 0 of the 2PULSE in pulse-width modulation mode to control the heating
element. In this mode, the 2PULSE generates a pulse train on the digital output DO (24 V
control signal) with a specifiable ratio of pulse duration/period to control the switching
element.
Technological Functions
Operating Instructions, 02/2007, A5E00124867-05
Heating a Liquid
control signal.
times of the switching element and heating element.
2PULSE
5.4 Application Examples
295