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Circuit Allowing Oscilloscopes to be Automatically Adjusted

IP.com Disclosure Number: IPCOM000048197D
Original Publication Date: 1981-Dec-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Picard, S: AUTHOR

Abstract

During the testing of various circuits on non-automatic testers, it is necessary to adjust manually the time base and the vertical amplifiers of oscilloscopes. Those adjustments may vary during the whole test, and currently 5 to 15 of such operations are needed for testing a single card. This procedure is tedious for the operator and time consuming. The device described below allows oscilloscope operation to be made automatic, provided that an "x axis" input is available. Time Base Generation Oscillator 1 feeds time base selector 2 either directly or via frequency divider 3. Under the control of five bits (Time Base Selection) it is possible to obtain at point "A" a frequency ranging from 25.6 MHz to 25.6/510/6/ MHz.

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Circuit Allowing Oscilloscopes to be Automatically Adjusted

During the testing of various circuits on non-automatic testers, it is necessary to adjust manually the time base and the vertical amplifiers of oscilloscopes. Those adjustments may vary during the whole test, and currently 5 to 15 of such operations are needed for testing a single card. This procedure is tedious for the operator and time consuming. The device described below allows oscilloscope operation to be made automatic, provided that an "x axis" input is available. Time Base Generation Oscillator 1 feeds time base selector 2 either directly or via frequency divider 3. Under the control of five bits (Time Base Selection) it is possible to obtain at point "A" a frequency ranging from 25.6 MHz to 25.6/510/6/ MHz.

The output of frequency divider 3 drives an 8-bit counter 4. This counter is reset to zero by the regular scope synchronization (external mode only).

Then the counter 4 will count 256 clock pulses issued from selector 2. The whole counting cycle will be 10 Mus to 50 seconds in accordance with the selected frequency. X Sweep Generation The eight outputs of counter 4 will drive an 8-bit digital to analog converter 5, the current output of which is converted to voltage by converter 6. The output of this circuit is routed to the "x axis" input of the scope. Then the spot of the scope will be displaced by an increment of 1/256 of the whole trace length.

Due to the fact that the original frequency (25.6 MHz) is crystal controlled and that the whole process is digital, the expected accuracy of the time base is mainly the accuracy of the digital-to-analog co...