Ogden, UT · May 10, 2001 · Automatic test equipment (ATE) typically uses voltage measurements to identify failures in electronic equipment. In practice electrical current (EC) measurements are very seldom performed. Typical EC measurements are collected using internal power supply sensors, and shunt resistors strategically distributed and inserted in the circuit. Two factors that widely contribute to limited EC measurements are: a) lack of non-intrusive electrical current sensors and probes, b) difficulty or inconvenience to interrupt an EC path (wire or printed circuit board filament). In order to measure EC, most existing ATE systems measure the voltage drop over a shunt resistor inserted in the circuit being tested or in the output terminals of power supplies. In some cases the shunt resistor is part of the circuit such as emitter loads in power transistors.
Instruments using new technologies such as programmable power supplies, and VXI/PXI instruments include internal EC sensors capable of providing steady state measurements by means of software commands. However, these sensors are not designed to capture the signals at high sampling rates, thus not allowing the capture of fast transient signals. Most EC measurements are steady state single measurements that are compared with upper and lower limits to provide a pass/fail test result. Very few of the existing test procedures collect and analyze EC time signatures (traces) or transient signals. Steady state information indicates the static performance of a circuit. Analysis of the transient portion of the EC measurement introduces new valuable information regarding the reactive or dynamic performance of the circuit. Reactive components can then be diagnosed by their dynamic performance. The capability of simultaneously measuring the complex voltage and EC provides new and valuable insight into the impedance. This parameter is rarely measured directly although it is very useful, especially in radio-frequency (RF) tests. EC measurements, combined with voltage measurements, also provide direct phase and bandwidth phase/magnitude response data.
The availability of EC data in addition to the voltage measurements increases the testability and diagnosability of electronic systems significantly. The development of software tools to collect and analyze EC data will significantly effect and revolutionize testing procedures. In order to facilitate the capture of EC data, non-intrusive sensors and probes capable of measuring EC signals, without interrupting wires or filaments in the circuit cards, terminals, and connectors are essential. In addition, software tools capable of capturing and analyzing EC data and correlating it with other classical measurements such as voltages, are widely needed.
The research being conducted will result in products that introduce an innovative capability for test equipment operators, repair technicians, and test software engineers. This effort provides a process to capture EC measurements as well as methods to extract and display steady state and transient EC information.
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