Abstract: A single cable, single point stimulus and response probing system allows the measurement of both low impedance stimulus measurements and high impedance response measurements using a single probe cable. Circuitry located within the probe cable receives stimulus input from the stimulus circuitry located within a test and measurement device, and delivers input to response measurement circuitry also located within the test and measurement device. Certain embodiments of the probing system use feedback supplied to an amplifier located within the stimulus circuitry to improve the accuracy of the measurement device and control output impedance. Feedback can be locally supplied from the output of the stimulus circuitry, or can be generated using an additional amplifier located within the response measurement circuitry.

Abstract: A method of fabricating an overcoated printed circuit board having a clean area free of contamination from the overcoating material. A metal-clad substrate is etched to form first and second printed circuit traces on the substrate. The first and second printed circuit traces define a channel having first and second ends. A layer of soldermask is deposited onto the substrate to cover a portion of the first and second printed circuit traces and to cover the channel except at an aperture. The aperture includes the intended clean area. The first and second printed circuit traces and the channel are covered with a capping device. An overcoating material is applied to the printed circuit board. During the applying step, the overcoating material is allowed to infiltrate into the channel under the capping device at the first and second ends, but is not allowed to reach the aperture.

Abstract: A system and method for injecting and canceling a bias voltage in an attenuated circuit is presented. The attenuated circuit is disposed within a tri-state logic-level measurement apparatus. The bias voltage is provided to ensure that when the measurement apparatus is floating, it floats at the tri-state voltage. In one embodiment, a summing network is connected to an attenuator, a first voltage generator which provides a bias voltage and a second voltage generator which provides a cancellation voltage. In another embodiment, a FET amplifier is provided in place of the summing network.

Abstract: A method for determining whether a circuit under test is open is presented. A digital-to-analog converter is dithered to generate a known signal. This known signal is summed with an external attenuation signal which is brought into the system from a probe on the circuit under test. This summation is then measured by an analog-to-digital converter (ADC). If the known signal is not attenuated by the probe (i.e., the ADC measures essentially the known signal), we can conclude that the circuit is open.

Abstract: A printed circuit spark gap for an overcoated printed circuit board. A metal-clad substrate is etched to form first and second printed circuit traces on the substrate. The first and second printed circuit traces define a channel having first and second ends. A layer of soldermask is deposited onto the substrate to cover a portion of the first and second printed circuit traces and to cover the channel except at an aperture. The aperture includes the spark gap. The first and second printed circuit traces and the channel are covered with a capping device. An overcoating material is applied to the printed circuit board. During the applying step, the overcoating material is allowed to infiltrate into the channel under the capping device at the first and second ends, but is not allowed to reach the aperture. Counter pressure buildup inside the channel, caused by the infiltration itself, stops the overcoating material before it reaches the intended clean area.

Abstract: A system for detecting open circuits is presented. The system comprises first and second digital-to-analog converters (DACs). The DACs, in combination with a microprocessor, generate a tri-state voltage which is fed through the system. This tri-state voltage is then attenuated via an amplifier. A probe carries an external attenuation signal via a measurement line through the system to be summed with the attenuated tri-state voltage to create V.sub.wts. An analog-to-digital converter then compares V.sub.wts with a known signal to determine whether the circuit under test is open.

Abstract: A low power high efficiency power supply provides a high voltage level output, which can be used to drive a variety of devices. The power supply uses controlled feedback to a comparator, which in turn drives an AND gate logic device. The comparator drives the AND gate logic device to gate an input clock signal the output of the AND gate logic being supplied to a resonant circuit that is at or near the resonant frequency of the input clock signal. The output of the resonant circuit is rectified to provide the final voltage output. The final voltage output is attenuated and supplied as feedback to the comparator.