A contact monitoring device for monitoring an electrical contact with a first contact state and a second contact state, wherein the contact monitoring device has the following features: an oscillator circuit which is configured to generate an excitation signal, a coupler with a signal input and a signal output, wherein the oscillator circuit is connected upstream of the signal input in order to apply the excitation signal to the coupler, wherein the coupler is configured to convert the excitation signal into a contact monitoring signal and to output the contact monitoring signal at the signal output for applying the electrical contact, wherein with the electrical contact in the first contact state, a first impedance value is set on the oscillator circuit, and with the electrical contact in the second contact state, a second impedance value is set on the oscillator circuit, and a detector which is configured to detect a version of the excitation signal in order to monitor the electrical contact, characterized in that the oscillator circuit is configured to generate a resonant oscillation with the electrical contact in the first contact state and the first impedance value and to output the excitation signal, wherein the oscillator circuit has a means for thermally stabilizing the oscillator circuit, wherein the oscillator circuit has an oscillating circuit with a feedback branch and an amplifier, where the amplifier amplifies the signal fed back via the feedback branch, where the amplifier has at least one transistor whose operating point is adjustable, where the amplification of the at least one transistor is stabilized by the means for thermal stabilization by adjusting the operating point. an oscillator circuit which is configured to generate an excitation signal, a coupler with a signal input and a signal output, wherein the oscillator circuit is connected upstream of the signal input in order to apply the excitation signal to the coupler, wherein the coupler is configured to convert the excitation signal into a contact monitoring signal and to output the contact monitoring signal at the signal output for applying the electrical contact, wherein with the electrical contact in the first contact state, a first impedance value is set on the oscillator circuit, and with the electrical contact in the second contact state, a second impedance value is set on the oscillator circuit, and a detector which is configured to detect a version of the excitation signal in order to monitor the electrical contact, characterized in that the oscillator circuit is configured to generate a resonant oscillation with the electrical contact in the first contact state and the first impedance value and to output the excitation signal, wherein the oscillator circuit has a means for thermally stabilizing the oscillator circuit, wherein the oscillator circuit has an oscillating circuit with a feedback branch and an amplifier, where the amplifier amplifies the signal fed back via the feedback branch, where the amplifier has at least one transistor whose operating point is adjustable, where the amplification of the at least one transistor is stabilized by the means for thermal stabilization by adjusting the operating point.