Abstract: The invention relates to a control circuit for a synchronous machine (1) of a dental handpiece, comprising a voltage supply (2) and a clamping circuit (7) connected by switches (6). The invention also relates to a method for determining an angular position of a rotor of a synchronous machine (1), wherein a power supply is switched off for a total period of time (T2), a clamping circuit (7) is connected for a time interval (T1), whereupon an electromotive force is measured, and the angular position is determined from the electromotive force.

Abstract: The invention relates to a control circuit for a synchronous machine (1) of a dental handpiece, comprising a voltage supply (2) and a clamping circuit (7) connected by switches (6). The invention also relates to a method for determining an angular position of a rotor of a synchronous machine (1), wherein a power supply is switched off for a total period of time (T2), a clamping circuit (7) is connected for a time interval (T1), whereupon an electromotive force is measured, and the angular position is determined from the electromotive force.

Abstract: A dental device having at least one pneumatically operable handpiece, the rotational speed of which can be influenced by a control element designed as a foot-operated switch, and a further handpiece, which can be driven by means of an electric drive, and the compressed air present at the pneumatic handpiece influences the control of the electric drive. A graduated filter is mounted on a pneumatically actuated hollow body and the graduated filter has regions thereon which can be sensed by a light barrier generating an electric signal in dependence on the properties of the regions.

Abstract: A HF surgery device had a microprocessor and a comparator which in combination generate a control signal which acts on a rectified operating voltage, which drive a HF generator. The HF generator can be modulated with a modulation signal. In order to automatically maintain the effective output power at a constant level in the event of a modulation of the HF generator, the microprocessor forms a reference value from the modulation signal and from a prescribed setting signal for setting a HF output power. The reference value is compared to the operating voltage in the comparator for forming the control signal.

Abstract: A circuit for controlling the speed of a subfractional horsepower DC motor has a driver stage with a switch that interrupts the motor current in repeated succession so that a pulse-like current is provided, and the motor EMF is sampled synchronously with the motor current interruption, with the sampled value being supplied to a comparator wherein it is compared to a rated value. The output of the comparator is used to control the driver stage which includes the switch. Two pulse duration modulators are provided which respectively independently control the motor current and voltage. The pulse duration modulator which controls the current generates pulse pauses which are always sufficiently long to permit the EMF measurement to be completed. The pulse duration modulator operates at a frequency above the audible frequency range so that its pulse pauses are short enough to prevent the motor current from noticeably failing or being completely interrupted.

Abstract: Dental equipment having means for delivering RF and LF energy to a dental handpiece. Given a supply of RF energy, the dental equipment transmits a further energy that is significantly lower-frequency in comparison to the RF energy or a DC voltage for supplying a lamp located in the handpiece without disturbing influences. A common transmission cable is provided for the transmission of the RF energy and of the energy for the lamp, this common transmission cable contains an inner conductor and a shielded line arranged coaxially relative thereto and has a third conductor for transmission of the energy for the lamp. This third conductor is arranged relative to the shielded line such that a high capacitive coupling exists between shielded line and third conductor.