Hewlett-Packard Company

Toshio Tamamura

Kiyoyasu Hiwada

Shinichi Tanida

Akira Hoshika

A voltage/current measuring unit includes a signal generating source having a digital error detecting unit and a digital-to-analog converter (DAC) connected in series, a current measuring resistor having first and second terminals respectively connected to an output terminal of the signal generating source and a connection terminal, a voltage measuring circuit connected to the digital error detecting unit for measuring a voltage at said second terminal of the current measuring resistor and for providing a voltage feedback signal to the signal generating source, a current measuring circuit connected to the digital error detecting unit for measuring a voltage across the first and second terminals of the current measuring resistor, and for providing a current feedback signal to said signal generating source, the voltage measuring circuit and current measuring circuit both include analog-to-digital converters for respectively converting a voltage appearing at the second terminal of the current measuring resistor and a voltage appearing across the first and second terminals of the current measuring resistor into digital voltage values that are fed to the signal generating source.

Voltage/current measuring unit and method

A test head comprising an electrically conductive cylindrical member for coupling to a device under test, a first path for connecting a first type of signal with the device under test, the first path being located outside the cylindrical member, and a second path for connecting a second type of signal with the device under test, the second path being located inside the cylindrical member, thereby preventing interference between signals of the first and second types. The first type of signal may be a digital signal and the second type of signal may be an analog signal.

Test head with improved shielding

A test head comprising an electrically conductive cylindrical member for coupling to a device under test, a first path for connecting a first type of signal with the device under test, the first path being located outside the cylindrical member, and a second path for connecting a second type of signal with the device under test, the second path being located inside the cylindrical member, hereby preventing interference between signals of the first and second types. The first type of signal may be a digital signal and the second type of signal may be an analog signal.

A measurement circuit includes two signal sources, one for generating a test input signal to a DUT and the other for generating a sampling signal. Both sources are coupled to one crystal oscillator and one or both sources may be fractional N oscillators. A phase locked loop stabilizes the sampling signal generated by the fractional N oscillator. The test input signal and the output signal from the DUT are separately mixed with the sampling signal and the resulting sampled signal are converted to digital values by A/D converters and stored in a microprocessor. The stored values can later be compared and analyzed by the microprocessor to determine the characteristics of the DUT.

Circuit for measuring characteristics of a device under test

A method and an apparatus for measuring settling characteristics of a device under test. A measurement system for measuring an input signal by sampling and digitizing that input signal is employed to obtain reference data by measuring a reference signal, at least one level of which is flat, and to obtain measurement data by measuring a second signal representing the settling characteristics to be measured but containing an error component due to inclusion of the measurement system itself. The error component is removed from the measurement data by adjusting the timing and level of the reference data relative to those of the measurement data.

Method and apparatus for measuring settling characteristics of a device

Apparatus for measuring the A.C. characteristics of an electronic circuit under test having signal generators and a signal measuring device synchronized by a clock signal from a control device. The signal generators and the control device are electrically isolated from the measurement device so that reference potential fluctuations in the signal generators or in the control device do not affect the measurement. The synchronizing clock signal is transmitted from the signal generators to the measurement device through a shielded twisted pair cable terminated at each end by a high impedence connection.

Apparatus for measuring circuit element characteristics with VHF signal

A device for evaluating the accuracy and dynamic response of a digital to analog converter (DAC). A digital word generator which provides inputs to the DAC and a sampler which samples the analog output signal from the DAC are triggered by a stream of clock pulses. Clock pulses for the sampler pass through a fixed delay line, to provide time for the DAC to stabilize. Clock pulese for the digital word generator pass through a pulse swallower capable of eliminating clock pulses to phase shift the digital word input to the DAC one step with respect to the sampler trigger signal, to move the sampling point to the next step in the cycle of the digital input waveform.

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Hachioji, Japan

Toshio Tamamura