Abstract: Highly accurate time interval measurement is achieved for an electrical waveform. The electrical waveform is sampled and converted to a series of voltages, and the series of voltages is interpolated in order to form a time tag list, using interpolations that are optimized for time interval measurement and analysis. The time tag list accurately represents the times at which particular events of interest occur, and is used to generate displays and results analysis such as adjacent cycle jitter and accurate differential triggering and analysis.

Abstract: A calibration apparatus for a programmable comparator is provided which does not need circuits for offset adjustment and gain adjustment or high precision parts makes possible inexpensive construction of the apparatus itself, and at the same has a wide adjustment range and can carry out high precision calibration. The programmable comparator compares the analog voltage value corresponding to a supplied digital code and the voltage value corresponding to the electric current value of an electric current supplied by a predetermined power supply point, and outputs the result. In the calibration apparatus, the power supply means supplies to a power supply point an electric current having an electric current value indicated, and an electric current detection means converts the electric current value of the electric current flowing through the power supply point to a voltage value, and this value is output to the programmable comparator.

Abstract: A digital oscilloscope automatically selects as the initial instance of a waveform parameter to be measured the instance that is both visible in the displayed trace and closest to the trigger reference point. Such a manner of automatic selection allows a greater amount of panning and zooming while the 'scope is subsequently stopped, without causing a different instance to become the measured instance, and also reduces confusion about continuity of measurement while the display is altered with the 'scope is still running. This automatically selected choice can still be overridden, if desired, by a manual selection. A further refinement is to, once an instance is automatically selected, retain it as the selected instance as long as it remains visible as part of a modified displayed trace, even if it would not otherwise become the selected initial instance if the measurement activity were first initiated with that modified trace.

Abstract: Disclosed is a waveform measuring apparatus in which an integration period T can be discretionally set to a value in accordance with the analog voltage cycle of the device being measured with a simple circuit configuration. The waveform measuring apparatus has an integrator circuit for integrating a fixed repeat-cycle analog input voltage during a period when a gate is ON and the waveform measuring apparatus converts the analog input voltage based on the integrated output of the integrator circuit.

Abstract: An apparatus for displaying a waveform of an input signal on a display includes a synchronization detecting circuit, a sweep generating circuit, a horizontal axis drive circuit, a switching circuit, a variable gain amplifier, a vertical axis drive circuit, and a vertical location arrangement circuit. The horizontal axis drive circuit drives the horizontal axis of the display on the basis of a sweep signal generated at the sweep generating circuit synchronously with a sweep trigger signal obtained by dividing synchronization detecting pulses from the synchronization detecting circuit by N (N-1, 2, . . . ). The switching circuit alternately transfers the input signal and a cursor signal at a high rate to provide a multiplexed input/cursor signal to the vertical axis drive circuit through the variable gain amplifier.

Abstract: The method and apparatus of the present invention vary the rate of movement of a marker along a waveform. The rate of movement is varied by changing the distance increment the marker moves in response to a movement command. In a first embodiment of the invention the marker movement increment is proportional to the reciprocal of the derivative of the waveform amplitude with respect to time. In a second embodiment the marker moves only to specified points of interest along the waveform which are calculated in real-time. In a third embodiment the increment depends on how long the input device has been activated. In a fourth embodiment the marker movement is interrupted when the marker steps onto or over a detent. Each embodiment of the present invention moves the marker along the waveform in a manner which improves the ability of the user to examine information of interest in detail while moving rapidly over information that is not of interest.

Abstract: A method of analyzing and displaying waveforms by acquiring an electrical signal, converting it into a stream of digital data points, and sequentially storing each data point to a memory device. Then, analyzing each of the data points to detect whether the data point is an anomalous data point outside of a preselected range. Until an anomalous data point is detected, the steps of acquiring, converting, storing, and analyzing data are repeated. Shortly after the anomalous data point is detected, storage of the data points to the memory device is stopped, so that the anomalous data point and adjacent data points are preserved in memory. Then, the anomalous data point is displayed, preferably along with the immediately preceding and succeeding data points.

Abstract: A method and apparatus for digitally sampling electrical waveforms. A sampling circuit for sampling an electrical signal, a digitizing circuit for digitizing the samples produced by the sampling circuit and an acquisition memory for storing the samples are employed, the acquisition memory being partitioned into a plurality of frames. Each frame is triggered to store samples associated with a respective triggering event. After substantially all of the frames have been triggered, the contents of the acquisition memory are retrieved from the acquisition memory, filtered in an equalization filter and stored in a waveform memory for ultimate display as an ET record under software control. A plurality of digitizing circuits associated with respective inputs of a multi-channel digital sampling oscilloscope are interleaved to increase the sampling rate.

Abstract: In the installation of a scanner of a position measuring apparatus, it is required that parameters such as amplitude and phase position of analog signals generated by a scanner be tested so that the scanner can be correctly installed. For this purpose, a control device with a display field is provided. In the display field, a bar is displayed whose width represents a measure for the range of variation of the radius and whose position represents a measure for the average radius of a Lissajous figure. In addition, a marking is displayed for the admissible range of variation of this radius.

Abstract: A signal scaling system and methodology for use in a signal measurement system such as a digital or analog oscilloscope, logic analyzer, network analyzer, spectrum analyzer or waveform generator that has a graphical user interface which controls a waveform display region on a display device. The signal scaling system determines one or more displayed waveform scaling parameters to cause portions of selected displayed waveforms appearing within a rescaling rectangle to occupy a predetermined portion of the waveform display region other than the rescaling rectangle. For each of the selected displayed waveforms, the scaling parameters may include horizontal scaling, horizontal offset, vertical scaling and vertical offset. Preferably, the predetermined portion of the waveform display region comprises the entire waveform display region and the selected displayed waveforms include all waveforms at least partially within the rescaling rectangle.

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: A signal from an original oscillation circuit is inputted into a phase-locked loop circuit capable of continuously varying a frequency of this signal derived from the original oscillation circuit. The phase-locked loop circuit changes the frequency of the signal derived from the original oscillation circuit into another frequency corresponding to sweep rate variable information derived from a sampling control unit, and then outputs the signal having the changed frequency. This signal outputted from the phase-locked loop circuit is supplied to a variable frequency dividing circuit. This variable frequency dividing circuit frequency-divides the frequency of the signal outputted from the phase-locked loop circuit at an arbitrary frequency dividing ratio corresponding to the sweep rate range information given from the sampling control unit, and thereafter outputs the signal with the frequency-divided frequency as a sampling signal.

Abstract: A graph displaying device and method whereby when functional expression data for producing graphs and the conditions of displaying the graphs are set, graphs for functional expressions data input in accordance with the conditions are displayed in corresponding colors on a display. First, functional expression data and corresponding color data which designate display colors of the graphs are input in corresponding relationship. In addition, range data which display coordinates and color data designating display colors of coordinates involved in the range data are input together. In response to this operation, the graphs for the input functional expression data are produced with the range data to which the color data are designated, the last-mentioned color data corresponding to color data which correspond to the functional expression data. The produced graphs and the coordinates are displayed in the corresponding designated colors.

Abstract: The phase of an acquisition clock for a digital oscilloscope is modulated by summing an offset voltage with the output of the phase detector of a phase lock loop. The offset voltage is generated by a digital-to-analog converter which is fed input values by a microprocessor running a number generator routine.

Abstract: An engine analyzer having a dual-trace digital oscilloscope display provides a discrete waveform plot area for each trace and displays in each plot area a cursor array which may selectively include one or two vertical-line cursors which can be selectively moved one at a time horizontally along the plot area. The movements of the two cursor arrays can selectively be either synchronized or unsynchronized. The scope provides alphanumeric indications of the position of each cursor, the waveform value at the point where each cursor intersects the waveform. When two cursors are displayed on a trace the scope provides alphanumeric indications of the distance between the cursors and the difference between the waveform values at the points where the cursors intersect the waveform.

Abstract: Each acquisition record in a random repetitive oscilloscope is time stamped and stored in a location in the acquisition memory indexed by the associated value of trigger offset. Those acquisition records that are older than a selected and variable amount can be discarded instead of being used to contribute data to the waveform record. This has the effect of preventing old data from intruding into a new measurement. When reformulating the waveform record to pan or zoom while using data already acquired, it is possible to ensure that the newest waveform records are included in that reformulation. This has the effect of ensuring that new data is displayed. The time stamp may be a binary count of an elapsed time interval, in units of the sample clock, since some cardinal event, such as the last time ERASE or RESET was pressed.

Abstract: Methods for producing logic signal displays for an instrument known as a "logic oscilloscope" are disclosed. A digital input signal is first sampled as an analog signal to produce multi-bit digital samples that are representative of the amplitude of the input signal over time. The multi-bit digital samples are then processed using interpolative techniques to ascertain when the input signal crossed a hypothetical logic level threshold or pair of thresholds and when the signal was in one logic state or the other. The resulting transition times and logic states are then used as the basis for generating a variety of digital displays, including logic timing diagrams, state table displays, and cursor readouts similar to those available in a logic analyzer. Setup and hold time violations and measurements may also be obtained using this information.

Abstract: An oscilloscope comprises a trigger circuit for initiating display of the waveform of an input signal in response to a trigger event, at least one detection circuit responsive to the input signal for detecting occurrence of an anomalous event therein, and a counter for reporting the number of occurrences of the anomalous event that have been detected.

Abstract: A first terminal of a device-under-measurement (DUM) is connected to the input of a buffer amplifier having its output applied to the inverting input of an operational amplifier through a resistor having the value "aR". A resistor having a value "R" is connected between the inverting input and ground. A second terminal of the DUM is connected to the input of a buffer amplifier having its output connected to the non-inverting input of the operational amplifier through a resistor having the value "ar". The non-inverting input is also connected to the output of a signal generator through a resistor having the value "r". The second terminal is also connected to ground through a load. An oscilloscope is connected across the outputs of the buffer amplifiers, and a computer controls the signal generator in response to a signal from the oscilloscope.

Abstract: In an oscilloscope having a video signal input, a video signal and the like can be monitored in addition to the normal waveform monitoring operation as the oscilloscope.

Abstract: An instrument is described for the measurement of optical and/or electrical signals, such as an optical time domain reflectometer (OTDR) or an electrical time domain reflectometer (TDR). The instrument includes a display to depict a waveform representative of measured signals, and can be operated by a few buttons, namely a start/stop button, a cursor-key and a select/confirmation-key. After adjustment of display parameters, almost the entire display is available for display of measured signals and data.

Abstract: The phase of an acquisition clock for a digital oscilloscope is modulated by summing an offset voltage with the output of the phase detector of a delay lock loop. The offset voltage is generated by a digital-to-analog converter which is fed input values by a microprocessor running a number generator routine.

Abstract: A system and method for process instrumentation and control equipment. The system including a paperless, microprocessor-based, panelboard recorder having built-in data acquisition functions, a mechanism for archiving data, and a variety of display types. Memory space is conserved by deriving quantized data comprising signal samples received at a first rate and storing them for a first relatively short period in a fine quantized memory, and storing in a coarse memory, for a longer period of time, a subset of said signal samples recurring at a rate lower than the first set and having fewer quantized levels than the first set of samples. The operator can then determine whether coarse data obtained over a relatively long period or fine data obtained over a shorter period are displayed.

Abstract: In a test instrument, display locking is reduced by the addition of a non-constant time delay to each acquisition cycle. The time delay may be randomly chosen or follow a predetermined algorithm. Decreased system throughput caused by the addition of a non-constant time delay may be minimized by alternately storing acquired data in two acquisition memories. Display locking may also be reduced by rejecting selected triggers. The data acquired from these selected triggers is not processed for display. The triggers whose data is not processed for display may be randomly chosen or they may be chosen by a predetermined algorithm. Rejecting triggers and the addition of a non-constant time delay may be used in combination or individually to reduce display locking.

Abstract: A new sampling technique for waveform measuring instruments (including methods and circuits for implementing same) comprises the step of processing a series of digital signal samples through a decimator to extract a decimated sample value from each decimated sample interval in a series of decimated sample intervals. The series of digital signal samples is simultaneously processed through a digital peak detector to extract maximum and minimum values (peak detect sample values) from each decimated sample interval. For a given decimated sample interval, a difference between the maximum and minimum sample values for the interval is calculated. If the difference exceeds a glitch detect threshold value, the maximum and minimum sample values for the given decimated sample interval are transferred to a video sample memory. If not, the decimated sample value for the given decimated sample interval is transferred to the video sample memory.

Abstract: A method and apparatus for generating a horizontally-magnified, scrolling drive-trace line on a graphical display screen of an engine analyzer aids a technician in controlling a vehicle's speed over a fixed driving period of successive driving time intervals. Toward this end, an initial drive-trace line is displayed on the screen representing the ideal vehicle speed at which the technician should maintain the vehicle during a first set of successive driving time intervals. A movable iconic marker is displayed on the screen disposed along the displayed initial drive-trace line. The iconic marker is moved horizontally on the screen after each elapsed time interval until the marker reaches a predetermined position along the drive-trace line, after which time the drive trace line is scrolled.

Abstract: An acquisition memory for storing therein and reading out digital waveform data received from an A/D converter is made up of a dual port serial access memory which stores therein the waveform data in response to a first write clock and reads out the waveform data therefrom in response to a first read clock. A display memory for writing therein and reading out therefrom the waveform data read out from the acquisition memory is made up of a dual port serial access memory which stores therein the data in response to a second write clock different from the first write clock and read out the data therefrom in response to a second read clock different from the first read clock.

Abstract: A waveform measuring apparatus having a dummy readout circuit which applies first read signals of a same period as sampling signals to a read clock terminal of a FIFO memory during an interval between a first moment that a trigger enable signal is outputted from a prepoint counter when digital samples have been stored in the FIFO memory up to a predetermined number (a prepoint value) and a second moment that a trigger signal is generated by a trigger signal generating circuit. Concurrent reading from and writing to the FIFO memory is thereby permitted with a difference between the write pointer value and the read pointer value kept equal to the prepoint value. When a trigger signal is generated, digital data are written into the FIFO memory until the write pointer value catches up with the read pointer value and digital data are read from the FIFO memory by second read signals applied to it by a control unit. A display unit displays the waveform of the measured signal.

Abstract: An engine analyzer for plotting engine cylinder firing or spark voltage information, corresponding to distinct points of a cylinder firing waveform, in histograph form to assist in identifying a cylinder-misfire condition. In an illustrative embodiment, two traces are provided. The lower trace depicts a histograph, representative of the firing or spark voltage and engine speed of each cylinder over successive engine cycles. The histograph consists of successive pairs of adjacent, vertical histo-bars, each pair representing voltage and engine speed for a single cylinder. The first histo-bar in each pair represents the spark or firing voltage for a given cylinder and the second histo-bar represents the instantaneous engine speed measured over the duration of the given cylinder. The vertical histo-bar pairs are plotted sequentially from left to right, representing successive cylinder firings.

Abstract: In a digital oscilloscope, a sharp and fine line can be displayed at high horizontal resolution. The digital oscilloscope includes a memory for storing waveform data to be displayed; a display data output unit including sync signal generating unit for generating a sync signal and an output unit for reading the waveform data from the memory in synchronism with the sync signal to output said read waveform data; and an audio/visual color dot matrix plane display device including a display unit having dots arranged in a matrix form for color representation. The scan clock signal generator generating the scan clock signal in synchronism with the sync signal produced from sync signal generating unit, and the dot scan control unit sequentially supplying the display data outputted from the output unit in synchronism with the scanning clock signal to the dots of the display unit, whereby the content of the waveform data is displayed on the display unit.

Abstract: An oscilloscope of the following type is disclosed. Even though a main unit of the oscilloscope is horizontally placed, a display can be adjusted at an optimal angle. Also, while the main unit remains in such a position, press buttons can be depressed stably. An operating section is covered in the case of carrying the oscilloscope and knobs of the operating section, and the like, can be kept out of the way, thereby not hampering portability. An oscilloscope casing is divided into a display section and an operating section. A part of the top surface of the main unit is lowered and the operating section is placed on the lowered surface. The display section doubles as a cover for the operating section and is pivotally fixed to the top surface of the main unit via a hinge so as to freely open and close. The display section has a display screen inside and forms the top surface of the main unit and covers the operating section outside when the display section is closed.

Abstract: The multichannel oscilloscope has a dot matrix display device, advantageously an LCD, with an integrated controller and character generator for forming a display made up of a plurality of characters consisting of pixels on a display screen, a multiplexer device connected to receive data from a plurality of channels and send the data to the dot matrix display device for multichannel display purposes and an additional controller device for controlling the transmission of the data from the multiplexer to the dot matrix display device and for controlling the parameters of the display device. The additional controller device consists of two EPROM units only and a more expensive but versatile microprocessor chip is not necessary. The additional controller device alternately transmits instruction signals defining a position on the display screen and input data signals from the multiplexer device determining a character to be displayed at that position.

Abstract: An apparatus measures a repetitive signal, including a signal generating circuit to output the repetitive signal in accordance with first clock signals which are generated by a first clock circuit. A sampling circuit samples the repetitive signal in accordance with strobe signals to output sampled signals, the strobe signals are output by a strobe generator circuit. An output circuit stores the sampled signals and outputs a reconstructed signal based on said sampled repetitive signal.

Abstract: An electromagnetic field frequency and image magnetic forms quantum analyzer apparatus for collecting and evaluating magnetic field waves, which includes a sensor, a tape recorder for recording the waveforms, an oscilloscope for displaying the waveforms, film and video cameras to record the locations and wave images, a cassette recorder for recording and playback for studying the waveforms and can include a computer to display and dissect the waveforms.

Abstract: A trigger system for a digital oscilloscope operating in external clock mode. Every n pulses, the trigger system generates a trigger signal. The trigger system therefore provides a trigger every n samples of the input signal waveform.

Abstract: A digital oscilloscope of the type that processes (30) the digital waveform values of the waveform record using interpolation and/or decimation (81) to produce a main trace record (91) and first (92) and second (93) zoomed trace records, and uses those records to produce (40) a main trace display (65) and first (61) and second (62) zoomed trace displays is improved by providing (94) a first zoom box (63) encompassing that portion of the main trace (65) display shown in the first zoomed trace (61) display and a second zoom box (64) encompassing that portion of the main trace (65) display shown in the second zoomed trace (62) display.

Abstract: A split-path isolation amplifier (10) employs a transformer (30) in a high path (26) and a single-input, dual-output closed-loop optocoupler (66) in a low path (24) to achieve a flat, wide frequency response without need for frequency compensation adjustments. In a low path frequency region (106), the optocoupler provides all or most of the signal to the output. The isolation amplifier employs a substantially overlapped crossover frequency region (104) in which the high path signal is applied to a primary winding (28) of the transformer, and the low path signal is applied differentially to secondary windings (40, 42) of the transformer. At frequencies below the crossover frequency range, the signal from the optocoupler dominates as the signal coupled from the primary winding rolls off. At frequencies above the crossover frequency range, the signal coupled from the primary winding dominates as the signal from the optocoupler rolls off.

Abstract: Methods and apparatus are disclosed for using current detection in a test instrument to ensure validity of component test output. In a component test instrument that employs digital synthesis of a test stimulus waveform, voltage scan data and current scan data are successively acquired, the scan data being synchronized relative to the test stimulus waveform. The voltage and current scan data are stored in respective temporary storage buffers. Before displaying the data, a check for an open lead is conducted in a manner similar to a current scan. A zero current value indicates an open lead and the acquired scan data is disqualified from being displayed. Similarly, at the beginning of a component test operation, an open lead test is performed and the first voltage scan is deferred until a validity check confirms that the test leads or probes are in place. The disclosed methods and apparatus ensure that only valid data is displayed to the user.

Abstract: A "component test" function is provided in a low-power, portable test instrument like a digital multimeter. A test stimulus waveform is synthesized digitally, and a digital trigger signal from the synthesizing circuitry is used to trigger acquisition of measurement data. A single-channel front end acquires voltage scan data over one cycle of the test stimulus waveform following the trigger point. Current scan data is later acquired through the same acquisition circuitry beginning at the same trigger point relative to the start of a later cycle of the stimulus waveform, so that the voltage and current scan data, although acquired separately, are very closely synchronized relative to the stimulus waveform, as a result of which they maintain their phase relationship. Stored voltage and current scan data are aligned accordingly and concurrently displayed so as to form a Lissajous pattern on a small display.

Abstract: The present invention relates to a method for sampling an analog, periodic, measured signal, which is subject to a phase jitter. The misread signal is to be detected with a prior event. One measured value is recorded for each individual signal and each successive measured value recording is delayed by a time unit in which each measured value recording takes place in a fixed time grid with a prior event, and in which the point in time of the start of the signal is detected in the time grid and is stored, assigned to the recorded measured value.

Abstract: A method of signal analysis for establishing display scaling and stable triggering for digital oscilloscopes employs amplitude and time histograms to analyze an input signal and establish the required conditions. An amplitude histogram analysis method is first used to determine the minimum and maximum amplitude levels of the signal, and then a time histogram analysis method is used to determine the predominant time intervals occurring in the input signal. From these two analyses, vertical gain adjustments and time base settings adjustments may be made either manually or automatically, and triggering levels established to provide a stable, usable display.

Abstract: Temperature-dependent waveforms, variable with time, of the output characteristics such as current, capacitance, threshold voltage, and the like of a semiconductor device are measured and analyzed in a short period of time for accurately and quickly identifying deep levels in the semiconductor device. When a step voltage is applied to a terminal of the semiconductor device, the output characteristics thereof respond with a waveform I. After the elapse of a time t from the application of the step voltage, the value of t.multidot.(dI/dt) is measured and stored at a plurality of temperatures T. The recorded values are three-dimensionally displayed in a space coordinate system having an x-axis representing 1/T, a y-axis representing log(tT.sup.2), and a z-axis representing t.multidot.(dI/dt).

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: Methods for producing logic signal displays for an instrument known as a "logic oscilloscope" are disclosed. A digital input signal is first sampled as an analog signal to produce multi-bit digital samples that are representative of the amplitude of the input signal over time. The multi-bit digital samples are then processed using interpolative techniques to ascertain when the input signal crossed a hypothetical logic level threshold or pair of thresholds and when the signal was in one logic state or the other. The resulting transition times and logic states are then used as the basis for generating a variety of digital displays, including logic timing diagrams, state table displays, and cursor readouts similar to those available in a logic analyzer. Setup and hold time violations and measurements may also be obtained using this information.

Abstract: A digital storage oscilloscope capable of acquiring and displaying input signals over a wide range of frequencies, and automatically establishing, by menu setups or user selection, any of a number of cycles of an input signal for viewing. An input analog electrical signal is sampled at a constant rate and then stored in a fast-acquisition memory. A DSP and a CPU combine to provide an automatic time base which maintains constant width of displayed signals without changing the sampling rate. The time period of one cycle of signal is measured, and the number of digitized samples is reduced or increased by the DSP to provide constant number of samples in order to maintain a constant-width display despite any changes in the input signal frequency. Additionally, the oscilloscope horizontal display axis may be expressed in degrees per division as well as time per division.

Abstract: A data acquisition system such as a digital oscilloscope includes a central processing unit which controls the waveform memory, analog to digital converter, trigger generator, and display to automatically adjust the acquisition parameters to optimal values for a particular repetitive waveform received by the data acquisition system. The system initially optimizes the acquisition parameters for determining the length of the input waveform and then determines the input waveform length. Parameters are then determined for best frequency analysis of the input waveform, and the waveform is then frequency analyzed to determine its spectral content.

Abstract: A variable under operator control is set to a desired value by taking a pause when the value of the variable has been modified such that it would surpass the desired value. Upon meeting the desired value, the value of the variable is set to the desired value for the duration of a pause period, during which the value of the variable remains fixed regardless of further attempts to modify the variable. Therefore, even if the operator is careless, the variable does not pass over the desired values. The variable may represent a voltage or current, or the position of a cursor.

Abstract: A multi-channel trigger dejitter technique uses actual digitized samples from a repetitive waveform signal to correct for jitter in a hardware trigger signal. Interpolated samples are calculated between a set of the digitized samples about the hardware trigger signal, and a hardware trigger level is determined from the closest sample in time to the hardware trigger signal. The hardware trigger level is averaged with that determined from prior acquisitions to produce an average trigger level. The closest sample in time to the average trigger level becomes an averaged trigger signal, and the times for all the digitized samples for that acquisition, as well as all simultaneous acquisitions from other input channels, are adjusted according the difference in time between the hardware and averaged trigger signals. Over several acquisition iterations of the repetitive waveform the amount of jitter between acquisitions is decreased.

Abstract: A method displays a signal which represents the variation of light intensity in a processing chamber over time. The light intensity within the process chamber is detected to produce a voltage signal with a voltage amplitude which varies based on the light intensity within the process chamber. The voltage amplitude of the voltage signal is digitally sampled at a sampling interval to obtain sample values. Running averages of a preselected number of sample values are calculated and displayed on a graph. For each newly displayed running average, a rectangular box may be superimposed over the graph of the running averages in order to graphically display changes in slope. A computer is programmed to look for an anticipated sequence of slopes.

Abstract: An ac mains test apparatus and method. An audio frequency signal measurement instrument is provided with a circuit for testing the ac mains to which the instrument is connected. The ac mains is internally connected to a coupler which presents an attenuated portion of the ac mains to the low level input of the instrument. A switch is provided for selectively connecting the input either to an audio signal to be measured or to the ac mains portion. The coupler both attenuates the ac mains for input to the instrument and isolates the relatively high ac mains voltage from the low level input.