Electronic test equipment
Apparatus used for the evaluation of electronic components, subassemblies, and systems.
The galvanometer was an early electromechanical instrument that converted current into angular rotation of a needle pointer across the face of a scale. The instrument consisted of a fine wire coil mechanically connected to a pivoting element. The coil was located in the field of a permanent magnet so that when current flowed through the coil the induced magnetic field rotated the element, causing the needle to move across the scale. This instrument could be used as a voltmeter, since a higher voltage induces a larger current flow through the coil. The advent of the cathode-ray tube (CRT) enabled the development of another widely used instrument, the oscilloscope. The CRT translates voltage into the deflection of an electron beam, which visibly activates a luminescent phosphor inside the face of the tube. When a voltage is connected to the vertical plates, the visual representation on the CRT face has the amplitude and polarity of the voltage displayed as a function of time. See also Ammeter; Cathode-ray tube; Galvanometer; Oscilloscope; Voltmeter.
An important advance in electronic test equipment was the incorporation of circuits that directly converted the analog signal to be measured into a digital reading. The most significant impact of these converters was to enable a computer interface to the equipment to be set up allowing direct computer monitoring and control of the instrument. Other equipments were designed with embedded computers, which provided very sophisticated analysis of the data within the instrument itself. See also Analog-to-digital converter; Digital-to-analog converter; Embedded systems.
The best example of this enhancement is with spectrum analyzers. Digital signal processing (DSP) electronics have been included in these instruments which provide a frequency spectral analysis of the input signal. These instruments are widely used in the evaluation of radio communication signals, acoustic signal processing, and the analysis of mechanical forces and vibration. See also Spectrum analyzer.
The complexity and sophistication of electronic components and subassemblies became more complicated. Multiple test instruments were integrated to form rack-and-stack automatic test equipment, where the individual instruments were connected to a control computer by a common bus. These computer-controlled testers were very efficient at providing the input stimulus to the unit under test and monitoring the output response. See also Electronics; Integrated circuits; Logic circuits; Microprocessor; Signal generator.
The ability of automatic test equipment to sort out good from bad units is only the first requirement of modern production test equipment. Since the repair of defective units can be costly, the design and program development of test equipment frequently must include special provisions to provide failure-mode analysis. Information such as the probable defective component on a printed circuit board or the probable defective board in a system is of great value in efficient repair. Some test systems include fault dictionaries, supplemental tests after first failure, or even artificial-intelligence features to assist in repair.
