Are Main and Delayed time bases functions provided by most digital storage oscilloscopes? What factors determine the accuracy of the delayed time base and what are some representative values?
All digital storage oscilloscopes have one time base. Most companies' oscilloscopes either use a horizontal position control that allows very long post-trigger times, or they use a zoom that requires a long record length and for the desired time window to be in that record. Most digital oscilloscope time bases are crystal controlled and the time stability/accuracy is measured in parts per million. If horizontal position is used to provide long delays, then delay jitter from time base jitter can become significant.
Only Tektronix simulates the delayed time base operation found on analog oscilloscopes. Tektronix oscilloscopes calculate delayed time base accuracy in the same way as main time base accuracy, because there really is only one time base. The Tektronix simulation of delayed sweep allows a second triggering after delay to eliminate the jitter error. It also provides an intensified zone display depicting where the delay is positioned on the main sweep. The zoom method restricts the delay window to the main time base window, and restricts horizontal resolution to the main time base resolution. The Tektronix simulation allows a higher sample rate, and thus higher resolution on the delayed sweep acquisition.
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