Siemens Automation and Drives is launching the 3TK2826 safety relay for applications in the area of functional safety. The device monitors the functioning of sensors and actuators, as well as safe shutdown of the outputs. Up to eight functions can now be programmed on one device using DIP switches on the front panel. Users therefore save space in the plant and reduce acquisition costs.
Either one sensor with two contacts or two sensors with one contact each can be connected to the safety relay. These can be rectified sensor contacts such as NC contacts or contrarotating contacts in electromagnetic switches. Using cross-circuit detection, the device determines that the sensor lines of both channels are not electrically connected in the case of a two-channel connection. This rules out the possibility of the safety system failing due to damaged cables.
Other functions include setting of the debouncing time (10 or 50ms), autostart, monitored start, and startup testing. The function 'automatic start following voltage failure' is said to be of special interest to the water industry because it avoids the need for physically separate plants to be started manually following a power failure.