Abstract: An AC/DC voltage converter achieving a relatively low loss of power includes a rectifier circuit connected directly to a step-up converter circuit. The voltage converter further includes a storage capacitor and a resistor connected to outputs of the step-up converter circuit. One electrode of the storage capacitor is connected through the resistor to one output of the step-up converter circuit.

Abstract: An apparatus for determining the density of liquids and gases from the length of a period of an oscillator filled with a test sample, an oscillation amplifier being provided for its excitation which excites the oscillator in its mechanical resonance frequency via one or a plurality of actuators and which emits a periodic electrical signal, the period of which corresponds with the period of the oscillator or a multiple thereof. To make highly accurate measurements possible it has been provided that the actuators are disposed between the installation site of the oscillator or the housing of the oscillator rigidly connected with the installation site, and a countermass. In an alternative embodiment, the oscillator housing is eliminated so that the actuator or actuators are interposed directly between the oscillator and the countermass. A thermostatically-controllable plate and thermostatically-controllable elements may be used as in the previous embodiment.

Abstract: An apparatus and method for determining a characteristic of a resistor and/or an environment occurring as a voltage across a measuring resistor (e.g., a voltage across a temperature-dependent resistor) by comparing it with a reference value that occurs as a voltage across a reference resistor (e.g., a voltage across a temperature-stabilized reference resistor) to determine, for example, temperature. A total of four voltages are measured. That is, positive and negative currents are passed through the measuring resistor and the resulting first and second voltages across the measuring resistor are detected. Positive and negative currents then are passed through the reference resistor and the resulting third and fourth voltages across the reference resistor are detected. The difference between the first and second voltage and the third and fourth voltages is determined to eliminate the effect of thermo-electric voltages in the lines to the resistors and the lines of the contact terminals in the switches.

Abstract: A device for determining the density of liquids and gases uses an actuator to physically excite a sample of the material being tested. The oscillations induced by this excitation are detected by a sensor and amplified by an oscillation amplifier, and the amplified signal is used to drive the actuator in a closed-loop fashion. To compensate for errors in the density measurement process arising from non-ideal viscous effects of the sample, a phase change circuit or inverter may be shunted into the amplifier circuit to change the phase of the excitation signal. By observing the effects of the excitation phase change on the oscillation frequency of the sample, the sample's viscosity can be measured, and the system can compensate for its effects.

Abstract: A monolithic integrated high resolution analog-to-digital converter based on a charge balancing process, characterized in that the output of a charge balancing integrator is connected to the control input of a pulse width modulator. An output of the pulse width modulator controls the temporal activity of the feedback signal in the charge balancing integrator. The output of the pulsewidth modulator is also connected to a digital calculation circuit which evaluates the pulse width result of the conversion. The input of the analog-to-digital converter is connected to one input of the charge balancing integrator and the feedback signal from the pulse width modulator is connected to the other input.

Abstract: A density measurement instrument measures the density of a fluid by determining the frequency of oscillation of a vibrating tube filled with the fluid. An electronic excilation system vibrates the tube and the frequency of oscillation is representative of the density and the temperature. The frequency is accurately measured. A temperature control system controls the temperature of the fluid during oscillation by comparing a single temperature set point with the measured temperature of the sample. Based on this comparison, current in a first direction or in a second direction is applied to a Peltier element for heating or cooling the sample. Substantially continuous temperature readings and adjustments of the current are thus provided. The temperature information may be applied to an external data link or to a display.

Abstract: An apparatus for measurement of density, particularly of liquids and gases, by determination of the characteristic frequency of a tube-shaped bending-type oscillator which is filled with the measuring substance, which oscillator is connected with a tensioned body, the tension of which is dependent upon the temperature and/or the pressure of the measuring substance. The tensioned body is bending-slack (a string). A member is provided which guarantees that the deflection of the bending oscillator is transmitted to the string and the restoring force of the string is transmitted to the oscillator.