We have a 2203 scope and have set up a custom probe for a pressure transducer. It puts out 0.5 VDC at 0 psi and 4.5 VDC at 150 psi. These were entered as 2 points in a lookup table. The automatic ranges subsequently generated by PS6 for this are 0 - 20 psi, 0 - 60 psi, and 0 - 200 psi. The "custom range" (also seemingly called "scaled range") 0 - 20 psi reportedly uses 13% of the "input range", while the 0 - 60 and 0 - 200 psi ranges use 16% and 40%, respectively, of the "input ranges".

If I convert psi to volts from my lookup table, I get 0.533 volts being the width of the "scaled range" for 0 - 20 psi, 1.6 volts for 0 - 60 psi, and 5.333 volts for 0 - 200 psi. Then applying the 13%, 16%, and 40% factors reported above, I get the scope voltage input ranges as about 4 volts, 10 volts, and 13.3 volts, respectively. Presumably PS6 generates the custom/ scaled ranges so it can pick the best hardware input voltage range to use (by actuating the correct relays?) for each scaled range. 4 volts (0 - 20 psi) must correspond to the +/- 2 volts hardware input range (of which I'm using the subrange 0.5 - 1.033 volts), 10 volts (0 - 60 psi) must be +/- 5 volts, but what about 13.3 volts? This doesn't seem to fit any of the voltage range specs for the 2203. The next one bigger than +/- 5 volts is +/- 10 volts.

And a clarification on terminology - I'm able to choose 0 - 20, 0 - 60, and 0 - 200 psi from the dropdown menu for each channel, but these drop down boxes are notated as "input range" when one holds the mouse over them. These are really scaled ranges, not hardware input ranges, correct? That is, the scope has only the voltage ranges listed in the manual to work with, breaking each hardware input voltage range into 256 (2 to the 8th power) discrete values (the 2203 is an 8-bit scope).

I'm asking because I believe this has implications for triggering with a given choice of transducer. I couldn't get a given pressure spike with the pressure transducer described above to trigger on the 0 - 60 psi range, but it triggered reliably on the 0 - 20 psi range. I need to understand the range options before investigating further. I'll take into account the triggering hysteresis info provided in a recent thread in this forum. I may need to get different pressure transducers. Thanks.