Abstract: An improved current monitor for measuring current over a wide dynamic range. The current monitor includes a low current channel, a high current channel, and a switch for selecting the low current channel if the measured current is below a predetermined level and the high current channel if the current is above the predetermined level. The output of the high current channel is voltage encoded by adding a fixed offset. The current monitor determines that the measured current is from the low current channel if the reading is below the offset and from the high current channel if the reading is above the offset. A current level output device automatically outputs a decoded current reading based on this determination. The current monitor also incorporates a low current error compensation circuit to compensate for parasitic current when the current monitor is using the high current channel.

Abstract: A desktop computer having stereo audio input and output ports is used with an interface board to supply test tones to an audio device being tested. The interface feeds back the test device outputs to the computer audio input ports. The interface, under control of the computer, selects any two of several inputs from the device and attenuates the two signals to the optimum amplitude for analysis. The computer digitizes the audio inputs and simultaneously analyzes the signals by software operations in either time or frequency domain along with appropriate filtering to quickly obtain results according to standard test specifications.

Abstract: Wow and flutter of a tape player is measured by playing a recording of a constant frequency test tone, digitally sampling and storing each period of the tone over a test interval, subtracting the average period from each period to obtain deviation data, calculating the FFT of the deviation data, and then calculating power magnitude and wow and flutter. The apparatus includes an interface board which squares the signals from the player, and a desktop computer having a timing board for gating a counter for each square wave pulse to sample the periods, a memory for storing the samples, and a CPU programmed to analyze the samples according to the test method.

Abstract: A vehicle audio system is tested during vehicle assembly by a computer controlled system coupled to a vehicle data bus via a diagnostic connector. Radio settings are controlled via the data bus. RF signals bearing preset tones are generated according to computer command via an encoder and RF generator and coupled to the audio antenna base. A microphone in the vehicle detects tones from the speakers and a decoder analyzes the tones to determine whether a tone is correct. Certain speakers are selected for test by adjustment of Fade and Balance controls to check speaker connections. AM and FM SEEK function are checked to verify radio circuits and antenna connections.