The Solartron Electronic Group Limited

John Gerald Cook

Julian David Shaw

In a bipolar mark-space analogue-to-digital converter, two opposed-polarity reference voltages are applied to an integrator during a first conversion interval to balance a square-wave forcing-function signal and an input signal whose magnitude is to be measured, and a counter receives clock pulses at up and down inputs during application of the positive and negative reference voltages respectively. Subsequently, zero input signal is applied during a second conversion interval, and the inputs to the counter are interchanged, so that up- and down-counted pulses correspond to the negative and positive reference voltages respectively. At the end of the second conversion interval, the counter contains a digital representation of the input signal, corrected for zero drift. The application of the reference voltages is controlled by two level detectors which compare the integrator output with fixed detector levels, the magnitudes of which are chosen so that at zero input each reference voltage is applied for substantially half the period of the square-wave forcing-function signal. The operation of the converter may be coordinated by a microprocessor which is arranged to aggregate the counts of clock pulses accumulated by the counter during each cycle of the forcing-function signal.

Bipolar mark-space analogue-to-digital converter with balanced scale

A digital voltmeter for measuring an input voltage which can lie in any one of M successive ranges comprises an input scaling device which scales the input voltage to produce a voltage lying in a single predetermined range, and which also produces a range signal indicative of the range in which the input voltage lies. An analogue-to-digital conversion circuit then converts the scaled voltage to a corresponding digital signal which has up to N significant decade figures of resolution, where N&lt;M. The voltmeter has a display unit with M decades, each of which represents a fixed order of magnitude of the input voltage, and control means responsive to the range signal to direct the digital signal to the group of N adjacent decades of the display means appropriate to the magnitude of the input voltage.

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Farnborough, United Kingdom

John Gerald Cook