TZAFRIR SHEFFER
Pilots at 50 Ave, Seattle, WA

4716361, Dec 29, 1987

Jun 11, 1985

6/743622

Tzafrir Sheffer - Seattle WA

John Fluke Mfg. Co., Inc. - Everett WA

G01R 2700

324 60R

An apparatus for performing ratiometric capacitance measurements by comparing the output of a digital-to-analog converter with the voltage at a tap between an unknown capacitance and a first inherent capacitance of the apparatus. A common input voltage is supplied to both the series circuit, including the first inherent and unknown capacitances, and to the digital-to-analog converter which accomplishes attenuation of the input voltage in response to a digital value. The digital value is generated by a successive approximation register supplying a digital output relating the unknown capacitance to the known capacitance. The apparatus is adapted to ratiometrically measure the first inherent capacitance by supplying the common input voltage to a series circuit, including a known reference capacitance and the first inherent capacitance, such that the digital output of the successive approximation register relates the first inherent capacitance to the reference capacitance. The apparatus is further adapted to ratiometrically measure a second inherent capacitance by supplying the common input voltage to a series circuit, including the first and second inherent capacitances, such that the digital output of the successive approximation register relates the second inherent capacitance to the first inherent capacitance. The measured value of the unknown capacitance is then corrected by the amount of the second inherent capacitance appearing in parallel with the unknown capacitance during measurement thereof with reference to the first inherent capacitance.

5559427, Sep 24, 1996

Apr 4, 1994

8/222156

Mark E. Hinds - Seattle WA
Robert J. Lewandowski - Seattle WA
Thomas P. Locke - Woodinville WA
Tzafrir Sheffer - Seattle WA

Fluke Corporation - Everett WA

G01R 3102

324 66

An instrument and method for the troubleshooting and verification of copper-wire local area network (LAN) cable systems provides a series of resistance and capacitance measurements between all possible wire pairs using a pair of switch matrices and a software method for evaluating the measurements which are stored in a two-dimensional matrix. The stored measurements are evaluated against predetermined figures of merit and the decision pattern in matrix form is compared to that of a known good LAN cable system. Error messages responsive to mismatches are generated and presented to the operator via a user interface. Near-end cross talk (NEXT) isolation is evaluated using a mathematically calculated differential capacitance technique. Error messages are generated responsive to difference capacitance values larger than a figure of merit correlated to an acceptable level of NEXT isolation.

5629628, May 13, 1997

May 23, 1996

8/652767

Mark E. Hinds - Seattle WA
Robert J. Lewandowski - Seattle WA
Thomas P. Locke - Woodinville WA
Tzafrir Sheffer - Seattle WA

Fluke Corporation - Everett WA

G01R 2704

324628

An instrument and method for the troubleshooting and verification of copper-wire local area network (LAN) cable systems provides a series of resistance and capacitance measurements between all possible wire pairs using a pair of switch matrices and a software method for evaluating the measurements which are stored in a two-dimensional matrix. The stored measurements are evaluated against predetermined figures of merit and the decision pattern in matrix form is compared to that of a known good LAN cable system. Error messages responsive to mismatches are generated and presented to the operator via a user interface. Near-end cross talk (NEXT) isolation is evaluated using a mathematically calculated differential capacitance technique. Error messages are generated responsive to difference capacitance values larger than a figure of merit correlated to an acceptable level of NEXT isolation.

5436555, Jul 25, 1995

Jun 9, 1994

8/257597

Thomas P. Locke - Woodinville WA
Tzafrir Sheffer - Seattle WA

Fluke Corporation - Everett WA

G01R 3102

324 66

A LAN cable identifier for testing and identifying copper-conductor LAN cables in conjunction with a LAN cable test instrument is provided. Series combinations of resistors and diodes allow for both resistance measurements and polarity determinations for selected pairs of conductors of the LAN cable. Resistance values are chosen to allow for identification of each combination in order to diagnose wiring errors and to identify the particular LAN cable identifier. In addition, capacitance measurements are accommodated with minimal contribution to measurement error by careful orientation of the resistors and diodes so that the diodes may be reverse biased by a d. c. bias voltage provided by the LAN cable test instrument. The reverse biased diode junctions contribute only a small amount of shunt capacitance to the measurement.

4998072, Mar 5, 1991

Feb 20, 1990

7/482290

Tzafrir Sheffer - Seattle WA

John Fluke Mfg. Co., Inc. - Everette WA

H03K 513, H03C 150

328 14

The frequency resolution of a direct digital synthesizer is increased by varying the phase increment used to accumulate wave lookup table addresses between two integer values. The time periods during which the larger integer value is employed is proportional to a fractional part of the desired phase increment for providing an analog output at a selected frequency.

4951004, Aug 21, 1990

Mar 17, 1989

7/325359

Tzafrir Sheffer - Seattle WA
Eric Drucker - Seattle WA

John Fluke Mfg. Co., Inc. - Everett WA

H03B 1900, H03L 718

331 1A

A coherent direct digital waveform synthesizer, capable of generating a waveform in response to a decimally or other non-binary related reference frequency while obtaining the advantages of the use of a binary radix phase accumulator generating binary addresses for a waveform memory. The interface between these elements include a frequency converter including a voltage controlled oscillator and a further binary radix phase accumulator in the feedback path of a phase locked loop. A binary radix related digital waveform synthesizer may be thus made to produce non-binary related frequency waveforms coherent with a non-binary radix reference frequency source, and of decimal or other non-binary radix related resolution.

5045817, Sep 3, 1991

Sep 7, 1990

7/579032

Tzafrir Sheffer - Seattle WA

John Fluke Mfg. Co., Inc. - Everett WA

H03C 306, H03C 309

332117

In a direct digital synthesizer providing a frequency modulated output the modulation input is bit shifted and the rate of the direct digital synthesizer phase accumulation is controlled to provide enhanced FM deviation resolution.

4992743, Feb 12, 1991

Nov 15, 1989

7/436634

Tzafrir Sheffer - Seattle WA

John Fluke Mfg. Co., Inc. - Everett WA

H03C 150, H03B 1900

328 14

Arrangements are provided for generation of dual-tone waveforms utilizing direct digital waveform synthesis techniques and architecture and retaining the advantageous characteristics of direct digital waveform synthesis. Preferred embodiments feature combination of generated waveforms at an analog adder, a digital adder using a single digital-to-analog converter and at a single wave table, respectively, each providing particular hardware economies and operational advantages with respect to other preferred embodiments.