Abstract: An interface having nine connections between a probe and test and measurement equipment includes a fixed voltage source located in the test and measurement equipment, which delivers through a first connection a positive fixed voltage, and through a second connection a negative fixed voltage. A voltage-programming resistor located in the probe produces a signal that is delivered from the probe through one of the connections to the equipment to control a programmed voltage source. The programmed voltage is delivered as a positive programmed voltage through one pin and as a negative programmed voltage through a second connection. A probe identification resistor is located in the probe. An ohmmeter in the equipment measures the resistance of the probe identification resistor through one of the connections.

Abstract: A measuring device displays waveforms representative of electrical signals and includes a selector, at least one input terminal, and a graphical display. The graphical display is suitable to view a waveform thereon. The measuring device receives an electrical signal from the input terminal and displays a first waveform on the graphical display representative of the electrical signal. The selector is selectable to one of a plurality of positions and the measuring device selects a set of waveform data in response to each of the positions. The measuring device displays a second waveform on the graphical display representative of the waveform data.

Abstract: An improved current monitor for measuring current over a wide dynamic range. The current monitor includes a low current channel, a high current channel, and a switch for selecting the low current channel if the measured current is below a predetermined level and the high current channel if the current is above the predetermined level. The output of the high current channel is voltage encoded by adding a fixed offset. The current monitor determines that the measured current is from the low current channel if the reading is below the offset and from the high current channel if the reading is above the offset. A current level output device automatically outputs a decoded current reading based on this determination. The current monitor also incorporates a low current error compensation circuit to compensate for parasitic current when the current monitor is using the high current channel.

Abstract: A probe holder mounted to a main housing of an electronic thickness gauge, of the type having a remote probe connected to the main housing by an elongate cable, enables the gauge to be used in its initial configuration when the probe is out of the holder and as an integral unit when the probe is positioned in the holder. The holder may be retrofit onto an existing gauge by making it an integral part of a battery cover that replaces an original battery cover. A second embodiment includes a cylindrical remote probe holder having independent, dedicated sensors mounted at its opposite ends to facilitate switching from one type of sensor to another, a third embodiment provides multiple remote probes independently interconnected to the main housing by elongate cables, and a fourth embodiment mounts remote probes in a "V"-shaped housing to enable switching from a first probe to a second by rotating the housing about an axis of rotation.

Abstract: A volt meter changes the dividing resistance across the terminals of a voltage source between first and second different resistances and measures voltage across the dividing resistor at the different resistances to determine an accurate voltage source magnitude from the measured voltages and the ratio of second to first resistances despite an unknown source resistance.

Abstract: The present invention relates to a digital DC voltage and horse power multimeter device unitized in determining the voltage and horse power on a locomotive system. The meter is permanently mounted onboard the locomotive and is capable of instantaneous determination of the voltage reading and horse power to provide real time evaluation of the locomotive's functions. The meter is built into the voltage test panel, replacing the test receptacles, and is designed to prevent operator error in that a voltage range is not required to be set before the multimeter reads a desired voltage. The meter is capable of reading the main generator, a load shunt test millivoltage, and is capable of determining the horse power of a locomotive system. The invention is therefore a device for metering electrical energy and calculating the horse power on a locomotive system which is permanently installed which operates off the existing 74V DC accessory power and is safer due to the absence of manual range settings.

Abstract: A meter (10) is capable of use with a plurality of different sensor heads (16, 16b). The reading meter (12) includes a digital display (20), a processor (22) and memory (23), and an analog-to-digital converter (ADC 41). Each different sensor head includes a memory (32a) which carries at least the processing algorithm for the particular sensor. In operation, the reading meter (12) reads the detector head memory (32a), and loads the information so read into its processor memory (23). The raw sensor data is converted to digital form, and processed in accordance with the stored algorithm, to produce the desired display. In one embodiment, the detector head memory (32a) is read, and the information is serially coupled to the reading meter. In another embodiment, the serial data is converted to optical signals (634) for transmission.

Abstract: A potable electronic test instrument is adapted for the automatic testing of semiconductor diodes regardless of the orientation of the diode relative to the test probes. The test instrument supplies an a.c. sine wave test voltage coupled to the test probes. The maximum negative voltage and the maximum positive voltage are measured and compared against a set of predetermined open and short circuit values to obtain a decision of open, short, or ok for each value. The combination of the two comparisons is used to determine the device status according to a decision criteria. The diode status is accordingly displayed on the graphical display of the test instrument, indicating the device is open, shorted, a diode with a forward orientation or a reverse orientation with respect to the test probes, or of an unknown type. The diode forward bias junction voltage is displayed regardless of its orientation.

Abstract: A method of improving fault current measurement accuracy on a power line is disclosed. A first sample is obtained from a first input channel. A current magnitude is calculated from the first sample. The current magnitude is compared to a possible current saturation value. If the current magnitude is less than the possible current saturation value, a second sample from a second input channel is obtained, and the current magnitude is recalculated from the second sample. Lastly, the current magnitude is scaled by a scale factor. Also disclosed is an apparatus for improving fault current measurement accuracy on electronic reclosure control.

Abstract: An interface circuit (10) for use with electronic metering equipment (E) to provide a linear output response to an AC or analog input. An air core transformer (12) has a first coil or winding (12a) connected to a load (L). An AC current I.sub.LOAD is produced by the load and is coupled to a secondary coil or winding (12b) of the transformer. The transformer has an air core rather than a ferromagnetic core so to have no saturable core. Because no load is drawn by transformer coil, the voltage across a terminal of the coil equals the EMF induced in the coil. The EMF, in turn, equals the mutual inductance of the coils multiplied by the rate of change of magnetic flux linkages over time. The output from the transformer is applied as an input to an operational-amplifier (16) which has a high input impedance. Further, the amplifier is a low drift amplifier which performs a linear amplification of the input signal provided thereto.

Abstract: An auxiliary device (such as probe or the like) identification system for measuring instruments (such as oscilloscopes or voltmeters or the like) incorporates a commercially-available containing stored personality identification information, that is interrogated by the measuring instrument to establish correct operating mode, setup, and scaling to measure electrical signals provided by the auxiliary device. The measuring instrument includes an RF generator, a transceiver, and a demodulator to extract the stored personality information from the transponder.

Abstract: A gauge includes a probe for taking measurements, a microprocessor for processing the measurements taken by the probe; and a screen display for displaying the measurements processed by the microprocessor; wherein the screen display can be selectively operated in a first mode wherein the measurements are displayed on the screen display in a first orientation, and in a second mode wherein the measurements are displayed on the screen display in a second orientation.

Abstract: A variable color display system exhibits a display unit in a color in accordance with the value of a limit. The color signals are developed in accordance with the value of the limit and applied to a color control input of the display system to control its color substantially continuously.

Abstract: A digital multimeter is provided with a highly reliable seal at a connection interface between an upper and lower enclosure forming an enclosure. The multimeter also has a highly reliable seal at peripheral boundaries of operating elements disposed on a surface of the enclosure thereby providing a highly-reliable, water-proof and dust-proof mechanism at a low cost. A packing serves as an elastic sealing material and is disposed at the connection interface between the upper enclosure and the lower enclosure. The packing is pressed and crushed in a slant direction relative to the direction of the thickness of the enclosure thereby providing a sealing mechanism at the connection interface. The periphery of a rubber key serving as an operating element is sealed by a double sealing mechanism comprising an uneven face formed on a peripheral side and an even face formed on the upper enclosure.

Abstract: A multimeter is provided having an erroneous input prevention mechanism that allows more than one mode to be assigned to an input terminal hole located in a central section of a shutter board based on movement of a rotary switch. When the rotary switch is rotated, the first and the second drive-side protrusions formed at separate locations from the selector push away the first or second slave-side protrusions in the slave shell to rotate the shutter board about the center at the negative common terminal hole. Thus, only a specific terminal hole is in the open state. Even when the rotary switch is rotated to a predetermined position, the shutter board does not rotate to leaving the first input terminal hole in the open state.

Abstract: An integrated device test system (10, 40) having AC and DC measurement modes of operation comprises a drive circuit (11, 41), a programmable measurement unit (12) and a switch (18). The drive circuit (11, 41) may be a current mode drive circuit (11) or a voltage mode drive circuit (41). The drive circuit (11, 41) is coupled to the programmable measurement unit (12) and a device under test (64). In a DC mode of operation, the switch (18) is configured to couple a sense terminal (39) with one end of an isolation resistor (66). A second end of the isolation resistor (66) is connected to a pin (63) of the device under test (64). In an AC mode of operation, the switch (18) is configured to couple the sense terminal (39) with the drive circuit (11, 41) and the force terminal (35) of the programmable measurement unit (12).

Abstract: A method and apparatus for measuring magnetic fields with a magnetically sensitive probe which is introduced into a magnetic field and which transmits a measuring signal to a measuring device for evaluation. After activating the measuring device, a zero point is measured and automatically set and a correction value is calculated and stored. The probe is introduced into the magnetic field and the polarity of the magnetic field automatically determined. A peak value of a plurality of measured values is automatically stored and the measurement range of the device is automatically adjusted to the range of the magnetic field. Thereafter, the measured values are read out, the probe is removed from the magnetic field and the device is switched off.

Abstract: Electric apparatus responsive to currents and/or voltages having wide dynamic ranges incorporates ranging circuits for each input in which a multiplexer providing the ranging selection has a common input connected to the output of an operational amplifier providing the selective gain and has a plurality of outputs connecting selected ones of a plurality of series connected precision resistors in a feedback loop around the operational amplifier. A second operational amplifier is connected as a follower to the last output of the multiplexer so that the gain applied to the output signal is not distorted by the resistance of the switches in the multiplexer. For three-phase systems not having a neutral conductor, phase to neutral voltages with ranging are generated by subtracting a neutral-to-ground voltage produced from an artificial ground created by connecting three resistors in a wye across the phase conductors from the phase-to-ground voltages applied to the ranging circuit input.

Abstract: A digital tester includes structure for: automatically effecting AC/DC determination of an input signal and subsequent AC/DC switch-over of a measurement system, enabling high-response measurement; measuring a pulse width using a simple construction and having high reliability, by handling changes in an input potential as changes in potential zones; and storing the probes and test leads so that the digital tester is easier to handle for a higher degree of convenience in use. The storing of the probes enables each probe to be securely stored with the grooves; to enable the probes to be used in their stored positions; and to facilitate removal of the probes by a user.

Abstract: A capacitance measuring device incorporates the integrating analog-digital converter circuit of a handheld meter. The capacitance measuring device charges an unknown capacitance with a constant current until the voltage across the unknown capacitor reaches a predetermined voltage. At the same time, a reference voltage is applied to the input lead of an integrating circuit of the integrating analog-digital converter such that a corresponding proportional charge is stored in the feedback capacitor of the integrating circuit. The negative of the reference voltage is then applied to the integrating circuit so that charge is removed from the feedback capacitor at the same rate as the feedback capacitor was charged. A counter is used to determine the number of clock pulses it took to completely discharge the feedback capacitor and hence a reading of the unknown capacitance can be determined from the equation C.sub.X =I.sub.CHARGE *T.sub.2 /V.sub.TRIP.

Abstract: A multi-meter comprising a switch for selecting an object and a range of a thing to be measured, a display unit for displaying a value measured according to the object and the range selected by the switch, a measurement circuit including a Z-state measurement unit to measure a Z-state of the thing to be measured, in addition to the object to be measured, the Z-state being an unknown state, and a controller for controlling the switch, the display unit and the measurement circuit. The Z-state measurement unit includes a light emitting circuit having first and second light emitting diodes. The first light emitting diode is turned on when the thing to be measured is not at the Z-state and the second light emitting diode is turned on when the thing to be measured is at the Z-state.

Abstract: A display system comprises a display area for exhibiting in a selective color a digital value, comparator for developing a signal in accordance with a relation of the digital value to a limit, and color control for illuminating the exhibited digital value in a color in accordance with the signal.

Abstract: A multimeter with automatic measurement function setting and automatic recognition of measurement range includes circuitry having a high input resistance for carrying out the recognition of the type of electrical parameter to be measured. When the parameter being measured is recognized as an impedance, however, a low input resistance is automatically switched on, whereupon the magnitude of the impedance is measured at low input resistance and then is displayed, and if the range of measurement changes, the measurement procedure is repeated from the beginning.

Abstract: A digital, DC voltage meter device utilized for metering electric power on a locomotive system. This invention will eliminate the need to use a hand held meter to perform these functions. The meter is permanently built into the Voltage test panel, replacing test receptacles with a large 7/10' LED display that can be read day or night. It is designed to operate in temperatures from -32 degrees Fahrenheit to 158 degrees Fahrenheit. A three position spring loaded switch returning to the off position is used to operate the meter. The present invention is a custom DC voltage meter that is capable of measuring two voltage ranges on a locomotive system; 0-1500 Volts ("V") for main generator voltage can be measured when the switch is in the top position; and 0-75 millivolts ("mV") for load test shunt millivoltage can be measured when the switch is in the bottom position. The meter is also capable of displaying the Dynamic Braking Voltage when the locomotive's dynamic brake is engaged.

Abstract: A digital tester includes structure for: automatically effecting AC/DC determination of an input signal and subsequent AC/DC switch-over of a measurement system, enabling high-response measurement; measuring a pulse width using a simple construction and having high reliability, by handling changes in an input potential as changes in potential zones; and storing the probes and test leads so that the digital tester is easier to handle for a higher degree of convenience in use.

Abstract: An electronic circuit for measuring current in a working circuit is provided with a first operational amplifier having a positive input, a negative input, and an output connected to at least one in-line amplifier to form a first current path. A second operational amplifier having a positive input, a negative input, and an output connected to a differential amplifier is provided within the circuit to form a second current path. An input terminal is connected to the negative inputs of each of the operational amplifiers to provide a connection between the electronic circuit and the working circuit. A variable conductance component is connected in series between the input terminal and the negative input of the second operational amplifier to control the flow of variable currents through the two current paths.

Abstract: In a connector apparatus employed in a measuring system, a sensor is connected by releasable connector to a measuring unit to form a standard sensor connection eliminating any requirement for calibration. The connector apparatus includes a measuring circuit containing a setting line scanning program reading a plurality of setting switches in the connector set in ON/OFF states indicating the type of sensor and correction data employed by the scanning program for measurements made by the sensor.

Abstract: An electronic test instrument adapted for displaying only meaningful information notwithstanding the intermittent arrival of valid input signals due to probing operations is provided. Two independent measurement processes measure the input signal simultaneously. The first measurement process operates in a similar fashion to a digital storage oscilloscope (DSO) by successively sampling the input signal to produce waveform information which are selectively sent to an LCD display device which graphically displays the waveform. The second measurement process continually performs a stability assessment of the input signal by collecting a series of stability measurements of a selected input signal parameter, creating a moving average of the series, and comparing each new stability measurement to the moving average relative to stability criteria.

Abstract: A hand-held detector for determining whether the exposure to electromagnetic fields resulting from electric power lines, faulty wiring, and electrical and electronic appliances is within acceptable limits. The device includes a shielded pickup coil, a filter circuit having a transfer function which provides a distinct response in two frequency bands, a summing circuit which provides a voltage indicative of the detected levels of electromagnetic flux density in the two frequency bands, and a display circuit, to provide a visual indication of the detected energy level. The filtering circuit preferably includes a first, extremely low frequency (ELF) amplifier having an upper cutoff frequency of approximately 2 kHz, and a second, very low frequency (VLF) amplifier having a lower cutoff at approximately 6 kHz.

Abstract: The twice scaled waveform display apparatus combines a twice scaled factor indication with the autoscaled waveform display so that an input data quality indication is produced based on factors such as signal strength, wherein the twice scaled factor is used to modulate the size of the display that is presented to the user. Thus, the generated waveform occupies a predetermined portion of the display when the signal strength and/or other input data qualities are at an acceptable level. The size of the waveform presented to the user on the display is reduced in magnitude when there is a degradation in the input signal magnitude or other quality factors.

Abstract: An arrangement has a unit with at least one plug for pluggable module (MO1, MO2) that forwards signals to a processing and/or peripheral unit, so that the measuring range of the unit is adapted to the measuring range of the signals. The disclosed arrangement requires only one further module (MO1, MO2) for all measuring ranges, i.e., for all voltage and current ranges. The desired measuring range is set by the position of the module (MO1, MO2) on the plug. The invention has application in input and output component groups.

Abstract: A method for measuring various measurable variables with a multimeter includes specifying one of a plurality of measurable variables to be determined through a position of a measurement range switch and/or through a selection between various input connections respectively assigned to the measurable variables. Input circuits are assigned to respective measurable variables. A preliminary test is performed for at least one of the measurable variables to check if an input circuit is suitable for picking up an applied test signal, before an actual main measurement is carried out. A given input circuit is enabled for picking up the test signal only if the preliminary test has shown that the test signal is suitable for the given input circuit. An error signal is issued if a test signal being unsuitable for the given input circuit ensues. A multimeter for measuring various measurable variables includes a measurement range switch and/or various input connections for specifying a measurable variable to be picked up.

Abstract: A solenoid type voltage, polarity and continuity tester has a solenoid operated voltage indicator, and separate positive polarity, negative polarity and continuity indicators. In the circuit for the tester, the solenoid is arranged in series with the polarity and continuity indication circuits so that continuity of the solenoid can be verified when the continuity of a circuit being checked is positively determined. A polarity indication circuit is in parallel with a continuity indication circuit. The continuity circuit has a battery which is switched into a circuit having a high resistance when a voltage is applied to the tester to reduce battery drainage.

Abstract: The present invention involves measurement of an electrical current by means of a current transformer having the current to be measured passing in an axial direction through the current transformer, and the voltage induced thereby in the windings of the current transformer are used to produce a first voltage. A Hall effect is used in series with the current transformer to produce a second voltage measurement corresponding to the current measured by the Hall effect sensor. When the two measurements agree to within a predetermined value (typically 5% of the root-mean-square current values measured by each sensor) then the current transformer reading is used as the more accurate. Otherwise, the Hall effect current sensor is used as the more accurate current measurement.

Abstract: An exhaust gas temperature indicator for a gas turbine engine is disclosed in which data representing discrete overtemperature events occurring at different times is stored in a nonvolatile memory for later retrieval and display on an event-by-event basis. A character display is used to provide detailed digital, alphanumeric or other character information relating to each overtemperature event, such as the number, temperature zone, peak temperature and duration of the event. An indicator is provided for indicating the presence of unacknowledged temperature data in the memory device, and a maximum exhaust gas temperature value for an aircraft flight is stored. An analog display for continuously displaying current exhaust gas temperature values is provided in conjunction with a character display for displaying either current or stored values.

Abstract: A measuring instrument comprises a DC section for processing DC signals, an AC section for processing AC signals, and an OHMS sections for performing resistance measurements. A first switch is provided for selectively activating one of the three measurement sections. The measured value of the signal is digitally exhibited in a color which is controlled by a second switch in accordance with the measurement section selected.

Abstract: Pin electronics for an IC tester are built as an integrated circuit for testing the electrical operation of a device under test (DUT) by applying a test voltage to each of the pins on the DUT and measuring each resulting current. Typically, when the tester switches between the internal measure resistors, a voltage spike occurs on the pin of the DUT of a magnitude that may severely damage the sensitive circuitry on the DUT. Voltage spike suppression is included in the circuitry to minimize the effects on the DUT of voltage spikes.

Abstract: An adaptive loading circuit is provided for adaptively attenuating an alternating differential voltage that is produced by a magnetic sensor in response to the rotation of a wheel while maintaining noise immunity. The circuit includes an input for receiving an input differential voltage from the magnetic sensor via first and second input lines. A resistive divider network is included which has a resistive load serially connected to each of the first and second input lines and a plurality of adaptively selectable parallel resistive loads connected between the first and second input lines. Combinations of the parallel resistive loads are adaptively selected when the input differential voltage exceeds predetermined voltage thresholds so as to divide the input differential voltage into a selected portion thereof as an output differential voltage. In addition, the parallel resistive loads may be selectively switched out when the input differential voltage drops below a low voltage threshold.

Abstract: An analog-to-digital converter utilizes low-resolution and high-resolution conversion paths for precision voltage measurements. A first conversion made using a comparatively low resolution ADC is used to predict the reference voltage to one input of a null detector that receives the input voltage on another input, and effectively magnifies the voltage difference between its inputs. In a preferred embodiment, the duty cycle of a pulse-width modulator is adjusted to precisely adjust the reference voltage to provide a nulled (or near null) reading from the null detector. A low resolution ADC then converts the voltage from the null detector, which when added to the reference voltage, yields a final reading with 18-bit to 22-bit accuracy. The preferred embodiment is implemented to read the output from a pressure transducer and employs a binary search technique to rapidly adjust the duty cycle of the pulse-width modulator.

Abstract: A device for protection of a digital multimeter from misinsertion of an input plug. The device prevents misinsertion of the input plug into an input core having no concern with a selected function and generates an alarm sound when a function switch is unconsciously rotated disregarding insertion of the input plug in an input core. The device comprises a plug misinsertion preventing unit for preventing the input plug from being inserted into specified one of the plug inserts when a function except a specified function is selected, the specified function corresponding to the specified plug insert. An alarm generating unit for alarming when the function switch is operated in order to change a function under the condition that the input plug is continuously inserted in the specified plug insert. The plug misinsertion preventing unit comprises a rotating plate and a shielding layer cooperating with the rotating plate. The shielding layer selectively shields the specified plug insert.

Abstract: Apparatus is disclosed for measuring the fundamental voltage, fundamental frequency and the fundamental voltage divided by the fundamental frequency of the output of a device, such as an inverter. Through the use of an isolation amplifier connected across the output of the inverter and proper component selection, the output signal produced by the isolation amplifier is representative of the fundamental voltage of the output of the inverter divided by the frequency of the fundamental voltage. The output signal from the isolation amplifier is converted into a pulse having a fixed width w, fixed height h and period 1/f to produce a signal representative of the fundamental frequency of the output of the inverter. The output signal from the isolation amplifier is also rectified and applied to a multiplier along with a signal having a fixed width w, height E.sub.in /f and period 1/f and then averaged to produce an output signal representative of the fundamental voltage of the output of the inverter.

Abstract: A wide power range radiation monitor includes a pair of diodes with their cathodes interconnected and with an additional capacitor coupled in parallel to one of the diodes. The detector, of the radiation monitor provides two outputs, a low power output and a high power output, which outputs are connected to the anodes of the detector diodes. The arrangement of dual diodes and capacitance provide the diode detector of the monitor with a greater than 40 dB square law region.

Abstract: A volt/frequency meter includes LED arrays which provide bar-graph style meter displays of the instantaneous voltage and the frequency of a variable electric analog signal. Each LED in the voltage array corresponds to a predetermined voltage range and each LED in the frequency array corresponds to a predetermined frequency range. The meter is switchable among three different voltage scales and three different frequency scales. A separate LED flashes momentarily in response to the input signal crossing a user-determined limit set point which is adjusted through a knob on the front panel. The limit set point controls the operation of the frequency display such that the displayed frequency is the rate at which the analog signal crosses the limit set point.

Abstract: A dual meter mounting plate member carrying an ammeter and a voltmeter, the plate member having therein recesses to receive the voltmeter and the ammeter, the plate member being removably attached to within a battery charging casing, the ammeter being connected to the charging circuit and the voltmeter having terminals across the battery to be charged to indicate the state of charge.

Abstract: A meter provides an arrangement for the optional connection of its voltage circuit to a current path or to a calibration system. The arrangement includes an opening, provided in the housing of the meter for inserting a contact device connected to the calibration system, and a pivoting lever. On insertion of the contact device into the opening, the pivoting lever can be moved from an operating position, connecting the voltage circuit to the current path, into a calibration position connecting the voltage circuit to the calibration system. Consequently, the arrangement can be changed over between the operating position and the calibration position with a minimum possible cost.

Abstract: A digital multimeter includes a microprocessor control and a keyboard input. The microprocessor functions to control the display of parameters measured by the meter and displays such measured parameters. The keyboard includes switches to allow the user to select a parameter which is desired to be measured as well as a range of values for that parameter for use in measuring parameters of a device under test connected to the multimeter. The microprocessor communicates with the keyboard and functions to control a resistor and switch network to configure the multimeter to test selected parameters within selected ranges. The multimeter incorporates an overload protection function which compensates for an over-large voltage on the input leads of the multimeter, thus preventing damage to the circuit and to the multimeter.

Abstract: A wide power range radiation monitor includes a pair of diodes with their cathodes interconnected and with an additional capacitor coupled in parallel to one of the diodes. The detector of the radiation monitor provides two outputs, a low power output and a high power output, which outputs are connected to the anodes of the detector diodes. The arrangement of dual diodes and capacitance provide the diode detector of the monitor with a greater than 40 dB square law region.

Abstract: An instrumentation system includes a hand-held computer-based measuring meter having a visual display and a plurality of individual sensor modules that can be selectively coupled to the measuring meter for measuring one of a variety of parameters such as temperature, pressure, or the like. Each sensor module includes a sensor responsive to a particular stimulus, as well as a data memory for storing information about the sensor. When the sensor module is interconnected with the measuring meter, the measuring meter accesses the memory of the sensor module to input data corresponding to sensor type, an accuracy code, calibration point data, and a calibration date code. The measuring meter compares the calibration date code to the current date to determine whether the sensor module requires recalibration. The measuring meter uses the accuracy code data to determine the number of significant digits displayed by the visual display.

Abstract: An apparatus for the analysis of power quality and the effects of harmonic distortions on machinery or equipment. The apparatus is compact, portable, and non-invasive in that the apparatus can be operatively connected to an electrical carrier without power interruption. A display device is built in allowing graphical display of averaged or continuously updated measurements and analysis. A central processing unit analyzes measurements using Fourier analysis.

Abstract: A multimeter converts an input voltage into decibels. Preferably, the input voltage is converted into dbm. The multimeter includes a table of voltage values wherein each entry is associated with a given decibel value. The input voltage is compared with entries in the table to locate a first entry which is larger than the input voltage. A second entry having a lower value than the input voltage is then located in the table. A fractional value that is indicative of where the input voltage lies at a range between the first entry and the second entry is calculated using the first and second entries. The fractional value is added to a decibel value corresponding the second entry to produce a decibel value for the input voltage. The input voltage may be scaled down into an appropriate operational voltage range and then the calculated decibel value may be scaled up to compensate for this scaling down.