Abstract: A multimeter is provided with two slide switches, one switch providing a selection of four functions, i.e. "OFF", "AC", "DC/JUNCTION" and "RESISTANCE/CONTINUITY" and the other switch providing a selection of six range settings and a "JUNCTION/CONTINUITY" setting. The multimeter also has three input sockets for insertion of test leads. At least two of the combinations of the switches and sockets are incompatible, i.e. "AC" and "JUNCTION/CONTINUITY", and a current input socket and "RESISTANCE/CONTINUITY". An internal buzzer is incorporated in the multimeter to provide an audible indication to a user that an incompatible combination has been selected. The buzzer is preferably also used in junction and continuity test modes.

Abstract: An analog/digital converter wherein an analog input signal is applied to a variable gain input amplifier which has an output connected to a subtractor. Also connected to the subtractor is the output of a D/A converter, the input of which is connected to the output of an integrator. The subtractor forms from the output signal of the input amplifier and that of the D/A converter a difference signal which is used by a tracking circuit for generating tracking signals for the integrator. For the purpose of widening the dynamic range, the input amplifier contains four scaling amplifiers, one of which is connected by a selection switch to the output of the input amplifier. The scaling factors of the second, third, and fourth scaling amplifiers are 1/4, 1/16, and 1/64, respectively, of that of the first scaling amplifier.

Abstract: An oscilloscope having multiple controls, wherein control functions are selected from a plurality of functions. Controls are located adjacent to the oscilloscope display which indicate the control parameter label and control parameter values. The control parameter selection is implemented by software program control.

Abstract: Apparatus for displaying a plurality of remotely measured parameters. The data words representing the parameters have different scale factors and include a parameter identifier and a parameter value. The apparatus includes a decoder for determining from the parameter identifier the scale factor associated with a data word and a scaling circuit for scaling the parameter value. The scaling circuit can include binary dividers, one of which is selected by the decoder output. The scaled parameter value addresses a ROM which provides BCD digits for energizing a display unit associated with the parameter.

Abstract: A modular field strength measuring and indicating instrument that includes as one component a sensing module with a sensitive D'Arsonval meter movement and a receptacle for interchangeable plug-in type sensing modules for measuring an electrical condition, such as electrical power. The other component is a field strength sensing module that plugs into the receptacle and which includes a self-contained DC voltage source, a sensing antenna, a high-impedance, variable gain, linear DC amplifier operatively connected to the voltage source for amplifying the field strength voltage signal sensed by the antenna, and circuitry for transmitting the amplifier output voltage signal to the D'Arsonval meter movement for indicating the field strength detected by the instrument. The field strength sensing module may be used in the meter module interchangeable with other modules, such as modules for measuring RF power in RF transmission lines.

Abstract: An encoding apparatus provides range or other data as determined by the setting of a control or selection knob therefor. The encoding apparatus is intended for use with an instrument providing an output voltage representative of data within a range, and providing output signals indicative of the setting for the range control or selection switch of the instrument. The encoding device is adapted to fit externally of the instrument chassis and is mounted between the range selecting knob and the chassis. The encoding apparatus is non-invasive, requiring no connection to or modification of the internal components of the measuring instrument.

Abstract: A sensor communication system uses a shared analog signal to duty cycle converter for producing a comparison between a predetermined free-running triangular waveshape and a selected output signal from a plurality of analog signal sources such as process sensors, to convert the amplitude of the analog signal to a variable duty cycle signal. The variable duty cycle signal is subsequently converted to a digital signal which may be represented by a count stored in a counter counting clock pulses during the occurrence of the pulse width waveshape of the variable duty cycle signal. The digital signal is utilized as a digital word by a microprocessor operating in accordance with a stored program to produce a characterized digital output signal for use in a communication after conversion to a 4-20 ma control signal for communication and control in an industrial process control system.

Abstract: A ranged precision voltage monitor with out-of-range enunciator characterized by a power supply and reference voltage stage, a voltage sensing stage, and an enunciator stage. The power supply stage provides power for the monitor, and further provides a reference voltage and a sensing voltage. The voltage sensing stage senses and displays voltage levels within a predetermined range, and further senses and displays over-range and under-range conditions. The enunciator produces a first audible tone for under-range conditions, and a second audible tone for over-range conditions.

Abstract: A case for encasing a meter movement and its associated pointer comprised of an assembly at least a portion of which is transparent which completely encases the meter movement and pointer, connecting means for providing input signals to the meter movement through the assembly, a rear cover having openings for receiving the connecting means and proportioned to abut the rear of the assembly with the connecting means disposed within those openings, a scale of generally flat dimensions for displaying the parameter to be measured by the meter movement and indicated by the pointer which scale is held fixedly between the rear cover and the assembly in a position allowing a sweeping of the pointer across the face of the scale to indicate the level of the parameter sensed by the meter movement thereby allowing an exchange of the scale for some second scale without any possibility of physically engaging the pointer or the meter movement and causing damage thereto.

Abstract: An oscilloscope vertical calibration system is provided in which gain control elements in one or more vertical input channels are automatically controlled with respect to cursor voltages applied to the vertical output amplifier. Such calibration process is performed for each deflection factor setting either manually or automatically and the correct gain control signals are stored in memory.

Abstract: A hybrid integrated circuit data acquisition channel apparatus employing an operational amplifier fed by a low current differential bipolar transistor preamplifier having separate feedback gain and signal gain determining elements and providing an amplified signal output to a sample and hold and analog-to-digital converter circuits. The disclosed apparatus operates with low energy and small space requirements and is capable of operation without the sample and hold circuit where the nature of the applied input signal permits.

Abstract: The converter system includes a conventional N bit analog-to-digital (A/D) converter and also includes an automatic gain control circuit and DC offset circuit to alter the input analog signal to utilize the full N bit capacity of the A/D converter regardless of the amplitude of the input signal, within the range of the calibration of the system.

Abstract: A method and an apparatus for rating a thermometer probe, wherein the thermometer probe includes a small thermistor sensing element and a pair of conductors connected with the thermistor contacts and being supported upon a substrate. With the thermistor held at a particular temperature, the electrical resistance of the thermometer probe is measured and the difference between the resistance of that probe and a standard resistance is fed to a computer which operates a laser to encode a machine-readable character on the probe representative of the difference between the measured resistance of the probe and the standard resistance. In use, the probe is inserted in a readout and the readout senses the actual resistance of the thermometer probe which is dependent upon the temperature of the thermistor.

Abstract: Circuitry for use in a voltage measurement and display device provides automatic function change for measurement of AC or DC voltages. Voltage measurement in a predetermined mode (DC, for example), is assumed. Upon detection of an input voltage component exceeding a predetermined threshold of the other mode, (AC, for example), the measurement function is changed to that other mode. Upon detection of a component in the other mode, in a range between the predetermined threshold and a second (preferably lower) threshold, an annunciator is activated to alert the user to the presence of the other mode (AC) voltage, for manual activation of a function-selecting switch if desired. Thus, in a specific embodiment, automatic function changeover is provided upon detection of AC components exceeding a predetermined threshold, along with activation of an AC annunciator.

Abstract: An analog to digital conversion method and apparatus includes the use of a scaling circuit 15 to scale the magnitude of an analog signal D applied to ADC 4 to within an acceptable input range. A calibration circuit 16 generates a signal M indicative of the effect of the scaling circuit 15 upon a digital signal E produced by the ADC 4. An adder 14 adds the calibration signal M and the digital signal E of ADC 4 to yield a digital output signal N which is the digital representation of measured analog input signal A.

Abstract: The operating range for a process variable transmitter used as a pressure transmitter is selectively non-interactively adjusted by successively applying upper and lower range values (URV and LRV) of input pressure to produce an LRV output signal and calculating the URV and the Span which is equal to the difference between the upper and lower range values, i.e., URV-LRV, to produce outputs from the transmitter representing the new upper and lower range values corresponding to the calculated Span.

Abstract: A multielement-sensor measuring device having a number of sensor elements is provided with a switching means, a measurement means, a memory data extraction means and an offset and gain compensation means. In adjustment of the device prior to actual measurement, the sensor elements are sequentially switched over to the measurement means which measures their output and produces and forwards to the memory for storage offset and gain values according to the variation in offset and gain among the sensor elements. During operation, the stored offset and gain values are extracted from the memory by the data extraction means and used to control the offset and gain compensation means, whereby the outputs from the sensor elements are compensated so as to be made free from variation in offset and gain.

Abstract: An apparatus for measuring liquid level in a container, particularly the fuel tank of a motor vehicle, has a plurality of detector stages for sensing or detecting a plurality of liquid level ranges, whereby an indicator stage can be arranged to indicate a first, normal range of measurement, and a second, precise resolution can be obtained of at least a portion of the overall measurement range, without requiring an excessively larger indicator stage. This is accomplished by arranging at least two groups of sensing elements one above the other in the tank and connecting them to indicator elements via change-over circuits such that one range of measurement is made via one group of sensing elements and a second, more precise range of measurements is made via a second group of sensing elements.

Abstract: Portable multimeter, including an indicating subassembly for visualizing a measured value of a measuring variable to be examined, a processing subassembly for converting or adapting the measuring variable, separate housings for the subassemblies being connected to each other and having edges about which the housings are swingable for folding together into a rest position, control and indicating parts to be protected being disposed toward the inside of the housings in the rest position, a bead disposed in the vicinity of the edges forming a hinge and increasing the useful interior space of the housings, the hinge including at least one interacting hinge element being integral with each housing and rotatably connecting the housings together.

Abstract: A low cost volt/ampere meter for consumer use employs a single liquid crystal bargraph display and a simple voltage divider network to display both line voltages and appliance currents encountered in a residential environment. The instrument employs standard line voltage prongs on one end and a socket for accepting standard line voltage prongs on the other end. A range switch connects the instrument to read either voltage across the meter prongs or current through the prongs. When the prongs are inserted into a duplex receptacle and an appliance is plugged into the meter socket, current drawn by the appliance will be displayed on the bargraph when the range switch is selected to read amperes.

Abstract: A range switching device for an electric meter, e.g.

Abstract: A device for determining the operational costs of electrical devices. A case encloses a measuring instrument including a circuit which is connectable to a power source and to the device being checked. The instrument has a dial calibrated to give readings directly related to current consumption. The user applies the applicable energy rate at computation means on the case to determine the operational cost in a period of time.

Abstract: An input terminal adapted to receive 0 to 300 volts AC or DC is connected through AC or DC connecting circuits, coupled into the path by switches, and attenuating apparatus including a plurality of ranges automatically switched into the path in response to the amplitude of an input signal, to a buffer which includes overvoltage protection and provides a relatively high input impedance with a relatively low output or source impedance. A frequency counter is connected through a hysteresis amplifier, a digital volt meter is connected through an amplifier including 60 cycle filtering and an oscilloscope is connected through an independent gain amplifier to the output of the buffer.

Abstract: A metering and control system is provided which in one embodiment provides a continuous reading vacuum gage and a controller for activating relays when the vacuum pressures indicated by the gage pass through one or more set points. The controller comprises solid state electrical control circuitry which is separate from the meter, and which may be switched into the meter circuit for calibration purposes. The control circuitry is made up of individual circuits which may be individually adjusted to selected set points, as indicated on the meter. For this purpose, the meter is selectively switched to the various individual circuits. Then, the meter is switched back to indicate the vacuum pressures encountered in the particular system in which it is installed. As the vacuum pressures pass the various set points, the corresponding relays are activated.

Abstract: A fault indicator for indicating the occurrence of a fault current in an electrical conductor includes an externally viewable target which is positioned to a fault-indicating position by a trip circuit within the indicator upon occurrence of a fault current. The trip circuit is responsive to a magnetic field within a predetermined sensing plane generally parallel to the conductor. To increase the sensitivity of the indicator to the magnetic field of the conductor, the fault indicator includes flux concentrating pole pieces which form a low reluctance magnetic circuit between the circumference of the conductor and the sensing plane.

Abstract: A companding analog to digital converter for converting an analog signal into a variable length multi-bit binary word, the number of said bits being a function of the magnitude of the analog signal being converted relative to the high end of the range of magnitudes capable of being converted. The analog signal is temporarily stored and is attenuated by a predetermined amount. The attenuated signal is converted into a multi-bit digital word. A group of the most significant bits of said digital word are examined to alter the attenuation of the stored analog signal dependent upon its magnitude relative to the full scale. The attenuated analog signal is again converted into a multi-bit digital word which is temporarily stored. The group of binary bits initially stored together with results of the second conversion operation are combined to develop a multi-bit digital word whose bit length is a function of the magnitude of the stored analog signal relative to scale.

Abstract: A power level measurement system includes a power level sensor having a linear response to power level variations for power levels below a predetermined level and a non-linear response above the predetermined level, a DC amplifier and linearity compensator for measuring power and amplitude levels above the predetermined power level, a switched amplifier circuit containing a DC to AC converter circuit, an AC amplifier and a detector for measuring power levels below the predetermined level, means for determining whether the power level of the high frequency signal is above or below the predetermined power level and for accordingly selecting either the DC amplifier or the switched amplifier system in accordance with this power level, and display means for displaying the output from the selected amplifier system.

Abstract: An analog-to-digital tester having at least two distinct ranges of full scale sensitivity is provided. The tester includes signal conditioning means for receiving an analog measurand and digital display for displaying a value representative of the measurand. The signal conditioning means includes first and second attenuation levels differing by a multiple of at least 100 and circuit means for selecting the attenuation level corresponding to the magnitude of the measurand. The analog-to-digital converter circuit has full scale sensitivity over a first range and additionally full scale sensitivity over a second range ten times greater than the first range and includes range detecting means for detecting the magnitude of the measurand applied to the signal conditioning means and in response thereto selects the first or second full scale sensitivity range to thereby apply a digital value representative of the measurand to the digital display.

Abstract: A digital multimeter having a tone generating circuitry and operable in a tone mode of operation for providing an audible indication when a measured electrical characteristic has a predetermined relationship with a reference value. The audible indication may be provided when a voltage level exceeds a preselectable limit, such as 1 or 2 volts. Predetermined limits for resistance values may also be selected for actuation of the audible tone. The device may be utilized as a conventional multimeter when the tone mode is non-operative.

Abstract: A preamplifier circuit for a voltage measuring instrument which provides for noninteracting span and zero adjustments. Two voltage follower circuits are used. The first produces a current through the output resistor of the preamplifier proportional to the voltage being measured while the second produces a current through the output resistor proportional to a fixed reference voltage. For both amplifiers, the proportionality is adjustable by a potentiometer which modifies the feedback on the first amplifier and the part of the reference used as input to the second amplifier.

Abstract: Power measuring apparatus for electric appliances including interconnected male and female connectors for attachment to a source of power and to an appliance to be measured, a transformer having a primary winding in series with one of the conductors interconnecting the connectors, a potentiometer having a resistance element connected with the secondary winding on said transformer and a movable contactor, and an indicator connected between the contactor and one end of the resistance element, the potentiometer being calibrated in terms of cost per kilowatt-hour and the indicator being calibrated in terms of cost per hour.

Abstract: A multi-function alternating current meter having a voltage probe and clamp type current probe for sampling voltage and current of a alternating current line without physically breaking into the line. Components include the two input probes which are connected to a squaring circuit and compensated low pass active filters which are arranged for feeding the respective output signals into an analog summing amplifier. Subsequently the signals are fed into a calibrated output indicator. A scaled multiplier and phase lead/lag detector are included in the circuit. Switches are capable of rerouting the input signals through various components, and the various outputs are individually applied to the calibrated output indicator to indicate the A.C. line's power factor, phase angle, true power, apparent power, voltage, current, or lead/lag status, as selected.

Abstract: A cathode-ray tube for a multipurpose test and measurement or information display instrument is provided with multiple internal graticules. One of the graticules is permanently visible and functional at all times the instrument is in operation. Another of the graticules is formed in a manner such that it is not easily visible in normal ambient lighting conditions alone, but becomes plainly visible when edge lighted by suitable means.

Abstract: A portable battery-powered audio cable tester having two jacks for connecting with the cable to be tested. A signal light and push-button "short" switch are connected with the battery such that the light will go on when a cable not having a "short" is connected to the tester and off when the "short" switch is opened, indicating such absence of a short. A second push-button "check" switch is connected across the jacks such that the tester can be checked when a malfunctioning cable is connected and the signal light fails to operate. A three position toggle switch, for indicating whether the malfunction is due to a broken conductor or an open shield, is connected so as to alternately bypass the conductor and ground wires, following release of the "check" switch. The normally open toggle switch is flipped upwardly or downwardly, such that the signal light will flash at one of the two readings, i.e., broken conductor or open shield.

Abstract: A digital voltmeter device is disclosed which displays both the numerical value of a measured voltage and a visual representation of an input waveform. The device includes an electro-optical display matrix utilizing display elements arranged in lines and columns. In order to make maximum use of the display matrix for representing input waveforms, the peak-to-peak voltage of the input waveform is measured and utilized as a reference for an analog to digital converter having output signals which form the address signals for the display matrix. The peak values of the input waveform thus appear at the top and bottom of the display matrix respectively.

Abstract: The variable attenuator and variable current shunt of a battery-powered auto-ranging digital multimeter uses latching relays, each of which, since it is stable in each of its two switching states, requires only a current pulse to change its state. The circuit which operates the relays provides a drive pulse only when the desired relay state differs from the actual state, thus minimizing the power required, and includes a tank circuit for minimizing disturbance to the multimeter power supply. To ensure that the tank circuit can recharge, each relay is driven by a tri-state output.

Abstract: A photometer adapted for use with interchangeable calibration cards, comprising a galvanometer having a transparent cover over its indicator needle, the cover being provided with a slot along its edge which faces the center of the photometer, the slot being adapted to permit insertion of one end of one of the calibration cards into the covering, beneath the needle; a zone adjacent the galvanometer and the slot containing an orifice adapted to receive a photometer cell, a first control knob located on a side of the photometer for setting the photometer to its blank value; and a second control knob, for adjusting the wavelength of the photometer, having coded means thereon for corrolating various wavelengths of the photometer, produced by rotating the second control knob to various settings, to data contained on the calibration cards.

Abstract: A device for measuring the thickness of coatings, wherein a thickness gauge is electrically coupled to a circuit intended to convert the electric signal at the output of said thickness gauge into an electric signal proportional to the thickness of the coating. The conversion circuit comprises a peak detector whose output is electrically coupled to inputs of an automatic measurement range switching unit and a subtractor. Another input of the automatic measurement range switching unit is connected to an output of a reference voltage forming unit, its one output is electrically coupled to another input of the subtractor, another output is connected to an input of an adder, whereas a third output is electrically coupled to an input of a measuring sensitivity control unit. An output of the subtractor is connected to another input of the measuring sensitivity control unit whose output is connected to another input of the adder.

Abstract: A voltmeter comprising a diode detector, a square root converter and a linear amplifier each connected to receive the diode detector output signal, a resistance network connected to receive the outputs of the square root converter and the linear amplifier, means for selectively switching the resistances of the resistance network to change the proportion at the resistance network output between the signal from the square root converter and the signal from the linear amplifier to inversely match the response curve of the diode detector, and means for displaying the amplitude value of the resistance network output signal.

Abstract: A meter system for indicating a plurality of variables with a single meter comprises a first switch for selectively supplying one variable to the meter, a plurality of dial plates which are arranged such that one of the dial plates is selectively displayed in correspondence with the selected variable by means of a second switch arranged to be operated together with the first switch.

Abstract: The subject invention relates to digital multimeter instruments for the measurement of physical quantities and, more particularly, to increasing the effective measurement resolution and accuracy thereof. In one form, a multirange digital voltmeter is provided with scales and ranges in a 1-2-5-10 relationship. The voltmeter includes an analog-to-digital converter which is connected through a digital multiplier to a digital display. The multiplier provides multiplication ratios of 1, 2 or 5, depending on the selected scale. The displayed value will change in increments of 1, 2 or 5 units of the least significant displayed digit for a change of one unit of the analog-to-digital converter output, depending on the selected scale and corresponding multiplier setting. This allows the various scales to have at least approximately the same number of digital steps over their full ranges.

Abstract: An air core gage having a pair of coils in quadrature to drive a pointer has the first coil energized by a relatively constant reference current while the second coil is energized by a current which varies as a tangent function of the input quantity in order to drive the pointer through an octant of the gage. The current polarity to the second coil is reversed and the current is again varied in the same manner to vary the pointer through a second octant. Then, the reference current is applied to the second coil and the current is varied in the first coil according to the tangent function to drive the pointer through a third octant, and so on for a wide angle pointer drive. When the input quantity is a frequency, the driving circuit is conveniently a digital circuit including a ROM which stores the tangent function of the input quantity and a steering logic circuit which selectively applies the steady state and the variable signals to the gage coils to effect the appropriate pointer movement.

Abstract: Magnetometer instrumentation which processes the signals from an array of magnetometer assemblies wherein the need for multiple sets of motor driven resistors to change the gain of the signal processing channels is eliminated by the provision of an arrangement which utilizes multiplying digital-to-analog converters that are directly commandable by digital signals.

Abstract: This invention relates to the modification of a moving magnet type of a direct current reading meter wherein by the addition of an electro-magnetic coil, the permanent magnet of the meter is influenced by the magnetic field of the coil with respect to the current flow to provide a reading to indicate full scale values of a much lower current value than that of the basic movement of the meter.

Abstract: A temperature detecting device which comprises an electrical bridge circuit including four arms, a temperature responsive resistance contained in one of the arms, a resistance type potential divider having at least one intermediate terminal which represents an output terminal of the network, and switching means connected across two power source terminals thereof for inverting the connection of the potential divider in accordance with a temperature state, positive or negative, which is detected by said device, the respective divided portion divided by the intermediate terminal forming two arms of the network.

Abstract: This invention provides an apparatus for adjusting the scale and range of D'Arsonval pointer-type meters providing an uncluttered accurate readout particularly adapted for compact hand-held meters. Display wheels imprinted with numerals for a plurality of different scales are provided enabling the user to set, by manual rotation of a drive gear engaging a ring gear one of a plurality of desired ranges. The invention also provides for the simultaneous automatic selection or interconnection of circuit elements for driving the meter movement in accordance with the selected range.

Abstract: A voltage indicating meter is connected between the outputs of two high impedance operational amplifiers, the first of which receives an input signal to be measured through a range setting resistance dividing network and having a gain which can be set to one of a plurality of different values. A zero control network applies a bias voltage to the inverting input of the second operational amplifier for zeroing the meter. The non-inverting input of the second amplifier can be connected either to the output of the first operational amplifier or to a source of reference potential. When, during operation, the non-inverting input of this amplifier is connected to the source of reference potential, the one terminal of the meter is clamped to the bias level and the other receives a voltage proportional to the voltage of given polarity being measured and the meter needle swings in a given direction.

Abstract: Apparatus for measuring a high voltage in an ignition circuit, in which voltage dividing means has a first arm for connection to a point of measurement in said circuit and a second arm connected to a rectifying means. The output of the rectifying means is connected to means for matching impedance at the rectifying means to a direct current voltage display means connected to the output of the impedance matching means such that a displayed voltage is related to the high voltage in the ignition circuit. Low voltage measuring circuitry is also present which is connectable directly to the display means without the use of an impedance matching circuit.

Abstract: Apparatus and method for detecting the movement of a control device (such as a tuning knob) for controlling the input to a controlled device (such as a frequency synthesizer or display) operating in discrete or digital steps. The rotational direction of a single tuning device such as a "tuning" knob causes an increase or decrease of the frequency. The rate of movement of the positioning device determines frequency bandswitching in differing degrees of coarse to fine tuning modes. The utilization of rotational direction and rate of the device provides a single control for all tuning functions.The apparatus and method is useful in both open and closed (servo) loop systems.

Abstract: A plurality of measurement readout displays electrically insulated from one another are provided on a plate member, each of which displays is performed by making use of an excitable material which is capable of being visible only upon the application of a voltage thereto.