Posted Fri, 30 Sep 2022 19:48:17 GMT by User, Forum

I have a DSA8300 and 80C15 optical sampler. What is the recommended interval between running the Compensation procedure (Dark-level compensation) on this instrument? The manuals only seem to say that it should be done "frequently" (Quick-start manual pg 26), and that it should be done "before" doing various amplitude measurements (Printable Application Reference, pg 260 & others). I don't see any specification of the recommended interval in the Performance Verification manual. To convince my production team to do this measurement regularly (instead of just when test failures occur), it would be very helpful to have a specific, quantitative, recommendation for the frequency of doing the compensation rather than vague qualitative recommendations. What is the recommendation (measured in minutes, hours, or days) from Tek for the maximum interval between doing the dark level compensation on this instrument?

Posted Fri, 30 Sep 2022 19:53:18 GMT by Expert, Tektronix Applications

It's a common practice to run Dark-level compensation immediately prior to any testing. Typically you want your equipment to be powered on for at least 20 minutes to allow any temperature induced offsets equalize, then run Dark-level compensation, then proceed with taking measurements. Some measurements are very sensitive to Dark-level compensation. I don't think that there is going to be so much a time interval related answer but rather temperature related. Here's an application note that briefly describes this: https://download.tek.com/document/85W_15763_0.pdf. And the excerpt I'm referring to:
"Dark Level Compensation must be run every time the instrument’s temperature changes. For sensitive measurements, the Dark Level Compensation
should be run whenever the settings of the instrument are significantly
changed. This is critical for higher values of Extinction Ratio (cca over 10). For
the most accurate results, the Dark Level Compensation should be run with
horizontal SCALE (time/div) and vertical SCALE (µW/div) set to the same ranges
at which the measurements will be performed. Alternately, the signal level can
be monitored when no light is connected, and the Compensation run only
when the offset level exceeds a desired limit."

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