Abstract: An identification system with a reading device having a single turn transmission coil for continuously radiating alternating energy. A portable tag receives via a magnetic coupling, the energy from the reader and charges a storage capacitor to 5 volts. The capacitor is discharged rapidly during a time period less than the charging time period. This discharge of the capacitor powers a coded information transmission circuit during a small percentage of the duty cycle.

Abstract: Apparatus for decreasing effect of transition of more significant bits in D/A converter reference of A/D converter. A pair of D/A converters are connected in tandem to eliminate transition of more significant bits of half scale. Also, three D/A converters are connected in parallel with each being offset from one another so that the effect of bit transition is minimized and occurs at different steps in analog output.

Abstract: The differential linearity of an analog-digital converter is measured by a test method that eliminates the need for precision calibrated test equipment. A triangle waveform with a pseudo random period is applied to the analog/digital converter input. The waveform has a uniform amplitude probability density function. Therefore, any analog/digital converter input voltage has an equal chance of being sampled by the analog/digital converter. The number of times each possible analog/digital converter output code word occurs is counted by a microprocessor. These numbers are a direct measure of differential linearity with an accuracy described by the theory of repeated random sampling.

Abstract: One aspect of the present invention provides for apparatus for dynamically calibrating the internal offsets of the various range conversion paths as well as the overall offset of a successive ranging A/D conversion system over time and temperature variations. More specifically, this apparatus includes at least two time-gated integrator circuits which are respectively coupled to each of the range conversion paths of the conversion system. Each integrator is operative at predetermined times to generate a corresponding compensating signal in response to the digital code of one of the path conversion results. The compensating signals are used to dynamically calibrate the internal and overall offsets of the A/D conversion system. Further included in the apparatus are switching devices disposed at the input and feedback paths of the system to provide for appropriate system conditions at the predetermined calibration times.