Bosch Rexroth Ag

Karlheinz Panzer

Alexander Meisselbach

Rudolf Stenger

Reiner Vathjunker

Richard Knüttel

Peter Hartmann

In the case of a measuring device having a sensor supplied from an oscillator for a non-electrical variable and having a circuit arrangement downstream of the sensor for rectifying the output voltage of the sensor, interference pulses, which are superimposed on the output voltage of the movement sensor and are rectified when the output voltage of the movement sensor is rectified, falsify the measurement result. This is particularly true for spiked interference pulses having a high amplitude. In order to reduce such falsifications of the measurement result, the output voltage of the sensor is supplied to a ramp-generating circuit arrangement, in which the mathematical sign of the transmission behavior can be controlled. The mathematical sign of the transmission behavior of the ramp-generating circuit arrangement is controlled by a switching signal, whose flanks correspond to the zero crossings of the output voltage of the sensor. Such circuit arrangements can advantageously be used in measuring devices for non-electrical variables having sensors which are supplied with an alternating current. These include, for example, movement transducers having sensors which convert the position of a moveable component to an electrical output signal, in particular in the form of an electrical DC voltage. The moveable component may be the control piston of a pneumatic or hydraulic valve.

Circuit arrangement for rectifying the output voltage of a sensor that is fed by an oscillator

An electric circuit arrangement for controlling a solenoid-operated fluid valve.

Electric circuit arrangement for controlling a solenoid-operated fluid valve

In a Wien-Robinson oscillator, a negative feedback path and a positive feedback path are arranged between the output of an operational amplifier and a reference ground potential. The negative feedback path contains two resistors which are connected in series and whose common circuit point is connected to the inverting input of the operational amplifier. The positive feedback path is formed from two RC elements which are connected in series and whose common circuit point is connected to the non-inverting input of the operational amplifier. If the aim is to keep the amplitude of the output voltage from the oscillator constant, additional measures are required, which increase the circuitry complexity. In order to stabilize the output voltage from the oscillator with little complexity, a third resistor is arranged between the output of the operational amplifier and that end of the positive feedback path which faces away from the reference ground potential. The common circuit point between the positive feedback path and the third resistor is connected via diodes which are connected in opposites senses, to a positive auxiliary voltage and to a negative auxiliary voltage. The magnitudes of the two auxiliary voltages are of the same magnitude, and the diodes are connected such that they limit the voltage at the common circuit point. Oscillators such as these are used, inter alia, for feeding inductive or capacitive movement sensors.

Wien-Robinson oscillator with stabilized output voltage

When using solenoid coils in an explosion-hazard environment, in order that no sparks are produced in the event of a discontinuity in an electrical line leading to the solenoid coil, two or more identical zener diodes are connected in parallel with one another and to the solenoid coil. In order to verify the operability of all the zener diodes which are connected in parallel with one another and to the solenoid coil, the electrical values of the zener diodes and of the solenoid coil are measured before assembly. The total capacitance of the circuit arrangement is measured after assembly. The capacitance of the solenoid coil is subtracted from the total capacitance, and the remaining value is divided by the number of parallel-connected zener diodes. The result is compared with the capacitance of a single zener diode, with the magnitude of the difference between these values being used as a criterion for the operability of the zener diodes.

Method for detecting the operability of a number of identical zener diodes that are connected in parallel to one another and to a solenoid

An electromagnetic actuator with a control circuit, a combinational circuit and a power section as well as with a magnetic coil, which is connected via electrical lines to the output of the power section, the output signal of the control circuit is passed on to the power section only when, in addition to the output signal of the control circuit, the combinational circuit is fed a release signal. For safety reasons, current is to flow via the magnetic coil only when the release signal is simultaneously available. For monitoring the effectiveness of the combination of the output signal of the control circuit connected upstream of the power section with the release signal with respect to the current flow via the magnetic coil, the voltage of that line which is supplied with the operating voltage on activation of the power section is fed to an evaluation circuit. The evaluation circuit has a threshold switch, which converts the voltage fed to it into a switching signal. The threshold voltage of the threshold switch is slightly greater than the reference potential. The actuator is particularly suited for hydraulic or pneumatic proportional valves in applications with increased safety requirements.

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Schwebheim, Germany

Karlheinz Panzer