Abstract: A graphical user interface implemented with touchscreen technology with associated indicators for a test instrument is provided. A set of indicators is mounted around the periphery of the touchscreen display so that each indicator is associated with a set of labeled softkeys on the touchscreen. Each of the indicators is chosen to indicate a piece of basic information that is necessary to communicate to the user of the test instrument in an unambiguous manner using color, such as the presence or absence of a signal, the presence or absence of an error condition, or a status of the test instrument. Because each indicator is coupled to labeled softkeys in the touchscreen display, an action to press an associated softkey is directly linked to each indicator to allow detailed information to be viewed graphically on the touchscreen display.

Abstract: A multimeter having an elongated housing with a fixed recess for receiving a current-carrying conductor is provided. The multimeter is adapted to measure various parameters including a.c. and d.c. voltage, resistance, and a.c. current. On one end of the elongated housing of the multimeter is a C-shaped current sensor mounted around the fixed recess for measuring a.c. current in the current-carrying conductor and on the other end is a pair of test leads for measuring resistance, a.c. voltage, and d.c. voltage. The current sensor and the test leads provide input signals to an analog-to-digital converter (ADC) to obtain digital samples which are displayed as measurement results according to the selected measurement mode.

Abstract: A method of testing ADSL (asymmetric digital subscriber line) circuits is provided. A test instrument is connected to the customer premises end of the ADSL circuit, consisting of an ATU-C modem on the central office end and an ATU-R modem on the customer premises end, with a twisted-pair telephone line connecting the ATU-R and ATU-C modems. A remote test instrument is coupled to the ATU-C modem, typically on a semi-permanent basis in the central office, dedicated for testing multiple ADSL circuits by communicating with multiple ATU-C modems via a switch or router. The test instrument and remote test instrument communicate with each other in full duplex via the ADSL circuit using Internet Protocol (IP) data packets. The test instrument generates the upstream data traffic, controls the test sequence, and controls and coordinates the throughput test with the remote test instrument.

Abstract: A voltage indicator using a serial or sequential comparison voltage measurement technique. Reference voltages generated by a voltage divider are applied to inputs of a multiplexer which is driven by a counter to select one reference voltage at a time in sequence to be presented via an output terminal to one input of a voltage comparator. An input signal to be measured is applied the other input of the comparator. When the input signal matches or exceeds the reference voltage at the output terminal of the multiplexer, the comparator switches, providing an enable signal to a one-of-N decoder. The one-of-N decoder is also driven by the counter, so that outputs of the decoder and corresponding inputs of the multiplexer are addressed simultaneously. The outputs of the one-of-N decoder are connected to LEDs which indicate the voltage level or magnitude.

Abstract: A tweezer probe comprises a pair of arms (10) each made of a multi-layer printed circuit board. The outer conductive layers (20, 32) on each arm are etched to form a shield region (36) and a tip contact (34). The tip contacts (34) are connected to inner conductive layers (24, 28) by through-hole plating, the inner layers being etched to form connector wires (40) extending along the length of the arms to a connector region where leads (8) are attached. The arms (10) are substantially rigidly mounted together, with an adjustment mechanism (14, 72, 74, 76) being provided to alter the angle between the arms, the tips being moveable towards each other against the bias provided by the inherent resilience of the arms.

Abstract: A method of displaying digital samples with enhanced image details on a raster display using a limited set of brightness values is provided. Digital samples are interpolated and stored as pixel information in high resolution intensity memory. An adaptive mapping process maps the high resolution intensity information to low intensity brightness information in a manner so as to maximize image details. An equal number of brightness levels from light to dark are allocated in each column along the sweep. An adaptive recombination process combines past and present brightness information in a manner that best preserves image details when the temporal behavior of the display image is changing. A raster display device is employed to display the image which is stored in the display memory as pixels arranged by row and column.

Abstract: A voltage measurement instrument such as a digital multimeter is provided with transient overvoltage input protection. Internal walls are integrally molded with the instrument case and disposed in close proximity to the input receptacles and terminals to separate conductive surfaces and provide transient overvoltage barriers. Top and bottom wall portions are fitted together in tongue-and-groove fashion to increase the creepage and clearance path without increasing the linear distance between conductive surfaces. This arrangement also allows the instrument to maintain a low profile.

Abstract: A tweezer probe comprises a pair of arms (10) each made of a multi-layer printed circuit board. The outer conductive layers (20,32) on each arm are etched to form a shield region (36) and a tip contact (34). The tip contacts (34) are connected to inner conductive layers (24,28) by through-hole plating, the inner layers being etched to form connector wires (40) extending along the length of the arms to a connector region where leads (8) are attached. The arms (10) are substantially rigidly mounted together, with an adjustment mechanism (14,72,74,76) being provided to alter the angle between the arms, the tips being moveable towards each other against the bias provided by the inherent resilience of the arms.

Abstract: A test pattern produced by a television signal generator includes picture elements derived at least substantially from helper lines, and vertically adjacent picture elements of substantially different luminance derived at least substantially from the main picture lines, so that the engineer can readily determine by visual inspection whether or not the helper lines are being decoded.

Abstract: A test pattern is suitable for a television signal decoder which detects changes in the color content of a signal from frame to frame, and on the basis of these changes attenuates high frequency luminance components, and possibly switches its output between intra-frame averaged chrominance and high-frequency luminance signals and directly-derived signals. The test pattern has discrete areas within which a motion value representing the change in chrominance from frame to frame is constant, but different from the value in other areas. The areas also contain a high-frequency luminance component. Other areas have a hue which varies from field to field.

Abstract: A pulse-based local area network (LAN) cable test instrument provides a measurement of the cross-talk characteristic of a LAN patch cord as a function of frequency in order to evaluate its relative performance and workmanship of assembly. A LAN cable test instrument applies a test signal in the form of narrow pulses to a selected transmission line of a LAN patch cord while the cross-talk response induced in another transmission line in the same LAN patch cord is measured and stored as a time record in digital memory. The near-end and far-end pulse responses are separated in the time record, leaving only the near-end pulse response. The LAN cable test instrument analyzes the near-end pulse response by performing a discrete Fourier transform on the time record to provide cross-talk versus frequency information. The same test may then be performed on the far-end end of the patch cord to obtain a complete test of the quality of workmanship at both ends of the patch cable.

Abstract: In a measurement instrument, a display processor system and method for efficiently building a display image on a bit-mapped liquid crystal display are provided. The display processor system contains a set of bit plane images corresponding to predetermined images such as figures, menus, axes for a graphical plot, and other commonly needed images. Because the bit plane images are already processed and defined, operating on the display image becomes a simplified, high-level operation in which the desired image is constructed according to a display operation sequence. Virtual trace bit plane images are also employed to accommodate incoming measurement values which are appended to measurement traces, thereby causing the measurement traces to change rapidly. Virtual bit planes skip the intermediate step of constructing an entire bit plane image so that the displayed image may be more rapidly updated with the changing measurement traces.

Abstract: A test instrument for measuring the injection time of different types of electronic fuel injectors in a fuel injected engine is provided. The test instrument is coupled to receive an injection signal from any of a variety of fuel injector types and over a range of injection times and repetition rates. The injection signal is digitally sampled and stored in memory. The injection time is determined according to an algorithm executed by a microprocessor which operates on the stored injection signal to determine first and second edges, with the time difference between the first and second edges representing the injection time. The second edge must be followed by the injection signal being substantially equal to the battery voltage for a predetermined hold time in order to reject false edges occurring before the second edge.

Abstract: A method and apparatus for measuring very short time periods, or differences between two events, such as the delta-T between a trigger point on a waveform and a sampling clock edge of a digital oscilloscope. The delta-T measurements are made using the time-to-voltage transformation of an integrator. The output sweep ramp of the integrator is normalized to a fixed differential time and differential amplitude by correction current provided by a reference circuit that has a reference integrator substantially identical to the delta-T integrator. The reference integrator is operated at the same timing as the delta-T integrator, and an error correction loop furnishes the right amount of current to both integrators to normalize the peak voltage of both to a predetermined reference voltage.

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.