A programmable logic controller (PLC) is a device that is employed and programmed for controlling or regulating a machine or system. These controllers can be found in application areas in the widest variety of industries, e.g. in fully automated production systems, injection moulding machines and likewise in hardness testing machines.
A PLC is equipped with inputs, outputs, an operating system (firmware) and an interface that allows an application program (operating software) to be loaded. The application program stipulates how the outputs should be switched as a function of the inputs.
The operating system (firmware) ensures that the current status of the primary unit is always available to the application program. Based on this information, the application program can switch the outputs in such a way that the machine or system operates in the desired manner.
The PLC is connected to the machine by means of sensors and actuators. The sensors are connected to the PLC's inputs and communicate events in the hardness testing machine to the PLC. Sensors not only include probes and limit switches, but also force sensors (load cell). The actuators are connected to the PLC's outputs and make it possible to control the hardness testing machine. Examples of actuators include various servomotors for force application or axis activation.