Switching monitoring device

Abstract

A switching monitoring device for monitoring a switching operation of a relay switching contact of a relay includes a control terminal, a controller, and an impedance circuit. The control terminal is configured to apply a control signal for switching the relay switching contact to the relay switching contact. The controller is configured to produce an excitation signal. The impedance circuit has a signal input and a signal output, and the controller applies the excitation signal to the signal input. The impedance circuit converts the excitation signal into a switching monitoring signal and outputs the switching monitoring signal at the signal output for application to the relay switching contact. The controller is further configured to detect a change in a signal present at the impedance circuit and, if the change in the signal is present, detect the switching operation of the relay switching contact.

What is claimed is: 
     
         1 . A switching monitoring device for monitoring a switching operation of a relay switching contact of a relay, the switching monitoring device comprising:
 a control terminal configured to apply a control signal for switching the relay switching contact to the relay switching contact;   a controller configured to produce an excitation signal; and   an impedance circuit having a signal input and a signal output, wherein the controller is configured to apply the excitation signal to the signal input, wherein the impedance circuit is configured to convert the excitation signal into a switching monitoring signal and to output the switching monitoring signal at the signal output for application to the relay switching contact,   wherein the controller is further configured to detect a change in a signal present at the impedance circuit and, if the change in the signal is present, to detect the switching operation of the relay switching contact, and   wherein the signal input is bipolar with a first input connection and a second input connection, and wherein the signal output is bipolar with a first output connection and a second output connection, and wherein a first capacitor is arranged between the first output connection and the first input connection, and wherein a second capacitor is arranged between the second output connection and the second input connection such that the second capacitor capacitively couples the switching monitoring signal to the relay switching contact.   
     
     
         2 . The switching monitoring device according to  claim 1 , wherein the signal present at the impedance circuit comprises one or more of the excitation signal or the switching monitoring signal. 
     
     
         3 . The switching monitoring device according to  claim 1 , wherein the relay is configured to transmit signals in a first frequency range and the switching monitoring signal is in a second frequency range, and wherein the second frequency range has higher frequencies than the first frequency range, and wherein the impedance circuit has a higher impedance in the first frequency range than in the second frequency range. 
     
     
         4 . The switching monitoring device according to  claim 3 , wherein the controller is configured to produce the excitation signal in the second frequency range. 
     
     
         5 . The switching monitoring device according to  claim 1 , wherein the controller comprises a measuring circuit configured to monitor a change in the excitation signal. 
     
     
         6 . The switching monitoring device according to  claim 5 , wherein the controller comprises a signal generator configured to generate the excitation signal. 
     
     
         7 . The switching monitoring device according to  claim 6 , wherein the measuring circuit has a current sensor connected between the signal generator and the impedance circuit, wherein the current sensor is configured to detect a current flow between the signal generator and the impedance circuit and to provide a measured current value of the current flow to the controller, and wherein the controller is configured to detect a change in the current flow between the signal generator and the impedance circuit based at least in part on the measured current value. 
     
     
         8 . The switching monitoring device according to  claim 6 , wherein the impedance circuit is configured to galvanically separate the relay switching contact from one or more of the signal generator or the controller. 
     
     
         9 . The switching monitoring device according to  claim 1 , wherein the impedance circuit has an inductance connected downstream of the first capacitor, and wherein the inductance forms an oscillating system with the first capacitor between the first output connection and the first input connection. 
     
     
         10 . The switching monitoring device according to  claim 1 , wherein the impedance circuit has an inductance connected downstream of the second output connection, wherein the inductance forms an oscillating system with the second capacitor between the second output connection and the second input connection. 
     
     
         11 . The switching monitoring device according to  claim 1 , further comprising:
 a first coupling capacitor, a second coupling capacitor, and a signal monitoring circuit, wherein the first coupling capacitor is configured to connect to the first output connection and the second coupling capacitor is configured to connect to the second output connection, wherein the first coupling capacitor and the second coupling capacitor are connected to the signal monitoring circuit and are further configured to convert the switching monitoring signal into a test signal and to provide the test signal to the signal monitoring circuit, and wherein the signal monitoring circuit is adapted to detect a change in the test signal and to detect the switching operation of the relay switching contact when the change in the test signal is present.   
     
     
         12 . The switching monitoring device according to  claim 1 , wherein the controller is configured to connect to the control terminal and apply the control signal to the control terminal. 
     
     
         13 . The switching monitoring device according to  claim 12 , wherein the controller comprises a switching controller configured to produce the control signal for switching the relay switching contact and to apply the control signal to a magnet system of the relay to switch the relay switching contact. 
     
     
         14 . The switching monitoring device according to  claim 12 , wherein the controller is configured to apply the control signal to a signal generator that is configured to produce the excitation signal with the control signal. 
     
     
         15 . The switching monitoring device according to  claim 14 , wherein the signal generator is adapted to generate the excitation signal as a periodic clock signal, and wherein the controller is adapted to detect a switching time delay of the relay switching contact, including detecting a time interval between the generation of the excitation signal and a change in the excitation signal when an impedance at the signal output changes, based on a constant period of the excitation signal. 
     
     
         16 . The switching monitoring device according to  claim 1 , wherein the controller has a control output, wherein the controller is configured to provide a status signal at the control output, and wherein the status signal is active after the relay switching contact is switched on and is inactive after the relay switching contact is switched off. 
     
     
         17 . The switching monitoring device according to  claim 1 , further comprising:
 a first damping element that follows the first output connection of the signal output, wherein the first damping element is configured to dampen high-frequency signals applied to the relay switching contact via one or more of the impedance circuit, an electrical load, or a voltage source coupled to the relay switching contact.   
     
     
         18 . The switching monitoring device according to  claim 17 , further comprising:
 a second damping element that follows the second output connection of the signal output, wherein the second damping element is configured to dampen high-frequency signals applied via the impedance circuit to one or more of the relay switching contact, the electrical load, or the voltage source coupled to the relay switching contact.