Abstract: A precision and high-speed analogue-to-digital converter has two separate groups of comparators linked by an intermediate network comprising a digital-to-analogue converter made up of current generators which are controlled by the logical outputs from the first group of comparators. These outputs represent the higher-order bits of the digital equivalent of the analogue input signal which is transmitted to the second group of comparators via a delay line. The digital-to-analogue converter causes a change in the threshold voltages applied to the comparators in the second group, which supply the lower-order digits of the coded input signal. The linking network further comprises means to compensate for errors at the inputs of the second group of comparators due to variations in the biasing currents of its comparators and also in the setting of their thresholds.

Abstract: A digital voltage level measuring device includes an amplifier having a capacitive feedback the output voltage of which is brought to a value dependent upon the integration result reached within a given interval of time of a voltage to be measured. After disconnection of the voltage which is to be measured, the output voltage is fed back to the amplifier input. The interval of time from the beginning of the feedback phase until the reaching of a given voltage value by the exponentially changing output voltage is then digitally measured.

Abstract: A method of and apparatus for determining when an unknown quantity is within a desired range of a reference quantity. The apparatus includes a dual slope integrator which integrates the reference quantity and the unknown quantity and discharges the resultant integrated levels. By integrating the reference quantity at least once and the unknown quantity at least twice for three different time periods which differ from one another by amounts which are proportional to the desired range, a comparison of the discharge times of the resultant integrated levels will provide an indication of whether the unknown quantity is within the desired range, when the desired range is a percentage of the value of the reference quantity.

Abstract: A digital meter incorporates a circuit which senses the input voltage and automatically energizes a digital readout device only if the input voltage is greater than a predetermined absolute value.

Abstract: A tristimulus colorimeter including a modified dual slope integrator digital voltmeter measures the red, blue and green light reflected from a sample and displays the same in digital form as optical density units. The colorimeter includes a light conducting probe with a diffusing member and a movable collar for blocking ambient light, and a rotating color filter wheel is synchronized with the voltmeter for effecting a continuous update of the data displayed thereby. Moreover, a color averaging method provides for prediction of the ultimate color of a mixture of two differently colored porcelains or the like especially used in the construction of artificial teeth or the like.

Abstract: An analog-to-digital converter adapted to utilize a counting circuit including a quartz crystal vibrator time standard as the time reference for effecting analog-to-digital conversion. The converter includes oscillator means for producing a time standard signal, and counter means including a plurality of series-connected divider stages adapted to produce timing signals representative of the counts thereof in response to the time standard signal. Coincidence circuitry is coupled to a first plurality of the divider stages to produce a signal in response to the coincidence of the count of the first plurality of counters and a preselected count of the coincidence circuit. Control means produce first and second control signals in response to the coincidence signal from the coincidence circuit and the timing signals from the remaining divider stages in the counter circuit.

Abstract: Elimination of an inverting amplifier and a video switch, which provide selective polarity reversal to permit usage of unipolar A/D conversion in prior art bipolar A/D converters, for improved economy and performance, is achieved by usage of two comparators, one for comparing positive input signals and one for comparing negative input signals, the output of one of the comparators, at any one time, providing the input to unipolar A/D converter successive approximation logic, and establishing the sign of the result.

Abstract: In a DVOM of the dual slope type, an unknown resistance or conductance to be measured is connected to a reference signal source to generate a voltage or current which is measured by the DVOM. However, if the input impedance of the DVOM is not extremely high, it loads the unknown resistance or conductance, and renders the relationship between the value of the unknown resistance or conductance and the actual voltage or current measured by the DVOM non-linear. In order to correct for this, a proportion of this actual voltage or current is algebraically summed with the reference signal used in the DVOM for generating the second slope of its dual slope operation, the proportion being selected in dependence on the input impedance of the DVOM (which can thus now take any convenient value) to linearize the relationship between the value of the unknown resistance or conductance and the output signal of the DVOM.

Abstract: An improved sweep circuit for an oscilloscope or the like has an adjustably delayed sweep which is time shared to display separate recurring events of interest alternately to provide an apparently simultaneous display of the events. The adjustable delay between sweeps may be directly indicated as a time interval between sweeps.

Abstract: Structure for and a method of detecting peaks in an electric signal comprising circuits for and the steps of converting a selected one of a plurality of analog signals into a current digital signal, comparing the developed digital signal with a digital signal previously developed from the selected analog signal and stored, and replacing the previously developed and stored digital signal with the current digital signal when the current digital signal is greater than the previously developed and stored digital signal and of the same polarity, and providing for readout of the currently stored digital signal in either analog or digital form.Direct reading of the digital output in terms of standard engineering units is provided for. Also, the analog input signal may be directly read at the output of the peak detector and the peak detector may be utilized as a volt meter with a direct current signal passed directly into a digital output portion of the peak detector.

Abstract: Method and apparatus for measuring the repetition rate of a series of electrical input pulses. An electrical quantity having a predetermined initial value changes at a predetermined rate in response to the presence of an input pulse; a later value of the quantity is detected in response to the presence of the next input pulse; and, in response to the later value of the quantity, an electrical output signal is provided that is indicative of the repetition rate of the input pulses. Typically the steps are repeated for a plurality of successive input pulses and a control signal maintains the detected later values of the quantity substantially equal to a predetermined comparison value. An alarm may be provided in response to any substantial change in the repetition rate of the input pulses.

Abstract: Centralized telephone circuit testing equipment with receptacles for selectively receiving a wide variety of electronic circuit modules, various modules being provided to make the equipment capable of performing a large number of commonly employed telephone tests. A scanning system is disclosed as part of the central measuring equipment for determining which of a plurality of remote testing stations has requested access to the central measuring equipment, one requesting remote station at a time being given complete control over a test function of the central measuring equipment for conducting tests on a telephone trunk.

Abstract: The analog-to-digital converter comprises a comparator having first and second inputs, and an output. A first switch is capable of connecting a signal to be measured to the first input and a second switch can connect a reference source to said first input. A capacitor is connected between said second input and the reference source and serves to store a charge fed by way of a feed back loop from the output of the comparator. The feed back loop includes current generator means arranged to provide a positive or negative current at the second input until the charge is equalized and change of state occurs at the comparator output. A selector means determines the polarity of the current from the generator means depending upon the state of the output from the comparator. A counter determines the number of counting pulses emitted from a pulse generator during a counting period in which the current generator means is applied to the comparator.

Abstract: This invention relates to a range changing circuit that operates in conjunction with a digital panel meter of fixed sensitivity. The circuit decodes the output of the panel meter and uses that information to change the gain of an input amplifier to the panel meter in order to insure that the maximum number of significant figures is always displayed in the meter. The circuit monitors five conditions in the meter and responds to any of four combinations of these conditions by means of logic elements to carry out the function of the circuit.

Abstract: Electronic analogue to digital converters of the integrating type wherein a capacitor is successively charged by an input signal and discharged by a reference signal, the time required for discharge serving as a measure of the amplitude of the input signal.

Abstract: The analogue to digital converter is of the bipolar mark-space type and includes an integrator for integrating the analogue input signal to be converted. A square wave generator is connected to the input of the integrator so as to superimpose a triangular periodic signal on the output signal produced by the integrator.First and second level detectors are connected to compare the output signal from the integrator with first and second detector levels respectively to produce first and second control signals respectively when the magnitude of the output signal from the integrator exceeds the first level and falls below the second level respectively. Switch means responsive to the first and second control signals are provided to respectively apply first and second reference signals. The conversion interval is set equal in duration to the duration of an integral number of cycles of the periodic triangular signal.

Abstract: A digital signal linearizer for obtaining a linear digital output from a non-linear input. The output voltage of a thermocouple is converted to a train of pulses by a dual slope analog to digital converter. The number of pulses in the pulse train is proportional to the voltage and is linearized by a pulse rate multiplier programmed to vary over successive ranges of pulse counts corresponding to linear segments approximating the non-linear characteristic relating temperature and voltage. The linearized pulse train out of the multiplier is counted and displayed directly in temperature units.

Abstract: A ramp type analogue to digital converter including an integrating circuit the output of which is first set to a level dependent upon the magnitude of an analogue input voltage to be converted. A reference signal is then applied to ramp down the integrator output level to a datum level and the conversion is effected by counting clock pulses while the integrator output is ramping down to datum level. The magnitude of the reference signal and the numerical weighting of the clock pulses being counted are scaled down by a common factor when the ramp reaches a value close to the datum level so that the slope of the ram is reduced and the resolution of conversion is increased as it approaches datum. Thus, compared with a ramp type digital voltmeter having a constant slope discharge ramp and a given resolution, the discharge time is reduced for the same resolution of conversions.

Abstract: In an analogue to digital converter the unknown voltage is applied continuously to an integrating circuit during each conversion period. An opposing reference voltage is switched on and off to cause the amplifier output to ramp up and down between two detection levels. One or both of these levels varies as a periodic function of time, e.g. a sawtooth waveform. Clock pulses are counted when the slope of the output ramp is of one sign only and it is shown that the ratio of the unknown voltage to the reference voltage is simply related to the number of clock pulses actually counted when the slope is of said one sign and the total number of clock pulses occurring during the conversion period.