I am seeing an interesting discrepancy between various Agilent scope products relating to the polarity reading of the Vertical Position/Offset.
On my Agilent U1602A handheld scope, if I adjust the waveform upwards on the scope (positive offset relative to zero baseline), indeed the numerical display shows a positive offset reading (e.g. Offset = +1.0 V)
If I do the same thing on my U1620A (a larger version of Agilent handheld scope), moving the waveform up causes a negative offset reading, and moving it down causes a positive offset reading.
This puzzles me, so I looked on another Agilent scope I have (4000 series) and it also shows a negative number for offset when moving the waveform in the positive direction.
I hadn't noticed this before, but typically I'm accustomed to expecting a positive offset resulting from a move upwards on the Y axis and find this counter-intuitive.
Can someone explain this behavior and the rationale? But whatever rationale exists, two handheld Agilent scopes work differently, which makes it even more puzzling.
I suppose it depends on your context for what is the "reference" --- but if I have, for example, a 0-5V square wave and the baseline (0 volts) is sitting on the center X-axis of the screen -- and then I adjust the waveform "upward" by, say 1 volt (such that now the waveform is between 1 and 6V, the display shows the offset as -1.0V. Really? Isn't the offset 1V? Or is it saying I need to "add" -1V to get the true reading? Of course, this is the same as subtracting 1V -- and it seems much more intuitive to think in terms of upward = positive offset, and downward = negative offset.
I'm interested in what others see on on their scopes and why different models of Agilent scopes would treat vertical offset/position differently.
Thanks!
On my Agilent U1602A handheld scope, if I adjust the waveform upwards on the scope (positive offset relative to zero baseline), indeed the numerical display shows a positive offset reading (e.g. Offset = +1.0 V)
If I do the same thing on my U1620A (a larger version of Agilent handheld scope), moving the waveform up causes a negative offset reading, and moving it down causes a positive offset reading.
This puzzles me, so I looked on another Agilent scope I have (4000 series) and it also shows a negative number for offset when moving the waveform in the positive direction.
I hadn't noticed this before, but typically I'm accustomed to expecting a positive offset resulting from a move upwards on the Y axis and find this counter-intuitive.
Can someone explain this behavior and the rationale? But whatever rationale exists, two handheld Agilent scopes work differently, which makes it even more puzzling.
I suppose it depends on your context for what is the "reference" --- but if I have, for example, a 0-5V square wave and the baseline (0 volts) is sitting on the center X-axis of the screen -- and then I adjust the waveform "upward" by, say 1 volt (such that now the waveform is between 1 and 6V, the display shows the offset as -1.0V. Really? Isn't the offset 1V? Or is it saying I need to "add" -1V to get the true reading? Of course, this is the same as subtracting 1V -- and it seems much more intuitive to think in terms of upward = positive offset, and downward = negative offset.
I'm interested in what others see on on their scopes and why different models of Agilent scopes would treat vertical offset/position differently.
Thanks!
The x-axis works the same way - the horizontal offset (or "delay") is the time of the reference point with respect to the trigger indicator. If you move the trigger point to the right, the reference point is moving back in time, a negative value.
I reconfirmed that the U1602A/B works in the opposite manner where the center line is always 0 volts and the offset/position adjusts the waveform up and down. As @ksmith stated in an earlier reply, maybe that model is the "odd duck" of the group. It would be nice to stay consistent between product lines, but at least I'm clear now on the thinking behind the way this works. Had I paid closer attention to the little "ground" symbol next to the channel number on the trace, I would have realized how offset was being computed and why it appears to be the opposite polarity of what you'd expect. The U1602A/B does not have the ground symbol next to the trace, since ground is always referenced to the center of the screen.