摘要:
A change in impedance of a electromechanical resonating sensor is utilized to detect and/or measure a change in mass accumulated on the sensor. The impedance is monitored at a fixed frequency. The fixed frequency may be at or near the resonance frequency of the sensor. In various configurations, the sensor comprises a quartz crystal microbalance sensor or a piezoelectric cantilever sensor.
摘要:
Conditions of a mechanical system driven (12) by a motor (14) can be assessed by monitoring an admittance or impedance at an input to the motor (14) over a period of time. The admittance or impedance may be determined by measuring the input voltage (22) and current (20). Variations in admittance or impedance are associated with known conditions including faults. An analyser (24) processes the admittance or impedance and provides a warning signal if a known fault condition is determined. The processing may be done using a neural processor.
摘要:
The invention relates to a method for ascertaining a resistance value (Z) between a first contact (2) and a second contact (3) in a subscriber line interface circuit (4), where a protective circuit (9) for protecting the subscriber line interface circuit (4) against overvoltages is provided between the two contacts (2, 3) and comprises a parallel circuit containing a protective capacitor (5) with two resistors (7, 8) connected in series via a node (K), the node (K) being connected to a third contact (10) in the subscriber line interface circuit (4), where the method has the following steps: a predetermined charging voltage (UCharge) is applied to the protective capacitor (5); a threshold voltage (UTH) is calculated on the basis of the resistance values (R1, R2) of the two resistors (7, 8) and the applied charging voltage (UCharge); a measured voltage (UM) tapped off across one of the two resistors (7, 8) is measured while the protective capacitor (5) is discharging; the measured voltage (UM) is compared with the calculated threshold voltage (UTH); a period (Δt) between the start of the discharging of the protective capacitor (5) and the time at which the measured voltage (UM) is the same as the threshold voltage (UTH) is ascertained; and the resistance value (Z) is calculated using the ascertained period (Δt) and the resistance values (R1, R2) of the two resistors (7, 8).
摘要:
A method and apparatus includes a signal generator, a power supply, a micro-controller a transmitter and a receiver for determining the condition of a line. The signal is passed through the line and any reflection is used to determine varying characteristics of the line.
摘要:
An apparatus for measuring electrical parameters for an electrical system measures a first and second parameters of the electrical system between connections to the electrical system. A processor determines a third electrical parameter of the electrical system as a function of the first parameter and the second parameter.
摘要:
An apparatus detects a position of an armature within a solenoid coil by superimposing a fixed frequency sensing signal onto the coil driver signal. The combined signal is applied to the solenoid coil and an alternating current component varies with changes in inductance of the solenoid coil that result from position changes of the armature. A current sensor produces an output signal indicating a level of current flowing through the solenoid coil and a filter extracts the alternating component of that output signal that results from the sensing signal. A position circuit determines the position of the armature from an output from the filter.
摘要:
A method and apparatus for resistivity mapping of semiconductor materials by causing currents to flow in a semiconductor body and measuring resultant potentials created between pairs of surface probes. A resistivity map is produced using the information gathered.
摘要:
Motor current and voltage waveforms are measured and converted to digitized current and voltage waveforms. A weighted discrete fourier transform is applied to the digitized current and voltage waveforms to obtain negative sequence current and voltage phasors; and the negative sequence current and voltage phasors are used to determine the existence of a turn fault. The use of the negative sequence current and voltage phasors can be performed by employing one of several techniques. In a first embodiment, an apparent negative sequence impedance is estimated by dividing the negative sequence voltage phasor by the negative sequence current phasor for comparison with a threshold negative sequence impedance. In a second, related embodiment, a current differential is estimated by dividing the negative sequence voltage phasor by a characteristic negative sequence impedance and subtracting the result from the negative sequence current phasor for comparison with a threshold current differential. In a third, related embodiment, a voltage differential is estimated by multiplying the negative sequence current phasor by a characteristic negative sequence impedance and subtracting the result from the negative sequence voltage phasor for comparison with a threshold voltage differential. In either of the second or third embodiments, the characteristic negative sequence impedance can be obtained by inserting a calibration device into one phase of the motor.
摘要:
A current in a circuit is measured without breaking the circuit. A relatively low resistance element in the circuit such as a component lead is chosen. A current is forced through the element and the voltage drop measured. Another current is forced through the element and the voltage drop measured. The values of these currents and voltages are used to determine the original current in the circuit.
摘要:
A system for measuring a broad range of impedance values with high precision and over a broad frequency band. Both the broadrange impedance measurement capability of the V-I method and the broadband frequency measuring capability of the reflection coefficient method are provided. A remote measurement capability is also available. Based upon the V-I method, a selection is made between a circuit to achieve an ideal open and a circuit to achieve an ideal short circuit in response to the impedance values. A boundary for selecting the impedance is, for instance, 50.OMEGA.. To measure a high impedance, the ideal open type circuit is selected; to measure a low impedance, the ideal short circuit is selected. The source and measuring instruments are extended by a coaxial cable. A floating measuring instrument is obtained by using a balun. Impedance measurements for 1 MHz to 2 GHz are possible.