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| Digital Oscilloscope Maximum Input Voltage |
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| Damianos:
@mike_mike By studying the oscilloscope manual you will find the right answers to your questions. For example: - the absolute maximum input voltage on the connector is 300V, regardless of the selected vertical range (page 9, 124 and the front panel of the instrument). - the AC input coupling is there for exactly what you want to do: it separates AC signals that are DC biased (page 82-83). - there is not any distinction depending on the coupling mode for the input impedance, so when using a division probe (x10, x100) the ratio is always the same. - it is referred two times the "probe compensation", in the "setup" and the "maintenance" sections, don't overlook it, affects the AC response of the system (the probe is part of the instrument). Measuring low level signals needs a careful setup to avoid traps, such as interference. Follow the manual, keep notes for what seems difficult to understand, continue asking and learn how to filter the answers that you get! |
| mike_mike:
Thanks for the reply. I saw another thing on my oscilloscope: if I set the time base to 25mS/div there appear a delay of the signal on the screen. So when I rotate the knob for the time base to 25mS/div, there appear a delay until the trace appear on the screen. If I set the time base to 5mS/div there is almost no delay. If I set the knob for 10mS/div the delay is smaller than the delay for 25mS/div. This happens on both channels. The probe is not connected to any signal source while I do these things. The voltage/division is 20mV/div. Is that normal ? |
| Damianos:
Yes, it seems that is the "normal" annoying operation that most (if not all) oscilloscopes do. They "update" the memory contents using the selected time base and then wait for a trigger event. I don't know why they do not simply discard any memory content faster. |
| David Hess:
Unless the DSO is operating in roll or scan mode, the display is only updated after the record is filled *after* the trigger event. So if the trigger is in the middle of 10 horizontal divisions, the 5 horizontal divisions to the right of the trigger point have to fill before the display is updated and at 25ms/div that is 125 milliseconds. I assume DSOs that have a huge number of horizontal divisions update the display based on only the display record because waiting for 5000 divisions to fill would be annoying. Roll and scan mode have no trigger so the display is updated immediately. Roll mode is like a strip chart recorder. Scan mode scans the display from left to right and then repeats. |
| mike_mike:
Thanks for the reply. I made a video with the calibration signal I noticed that there is a delay from the moment I connect the probe to the calibration signal and the moment when the signal appears on the screen. Also there is a delay from the moment I disconnect the probe and the moment when the signal disappears from the screen. Is that normal ? |
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