One reason I justified the purchase was last week I bought a used Resmed AirSense10 Auto and I wasn't completely certain it was functioning properly as it seems to deliver therapy quite differently than my DreamStation 2 comparing data in OSCAR and the mask check on the AS10 was almost impossible to get a good fit, where the DS2 had no problem. I'm confident now that the AS10 is delivering the correct pressure and I think I've likely got some tweaking of the settings to figure out (probably be posting some OSCAR screenshots in another thread).
I also can use the manometer to check the draft on my pellet stove and oil furnace .
The digital manometer is a 'RISEPRO Digital Air Pressure Meter and Differential Pressure Gauge' (about $43US with tax from Amazon). I had to cobble up an adapter to connect to the CPAP hose end and it's not pretty, but it works and didn't leak. The meter seems accurate and the read on the DS2 when delivering minimum pressure compared well on the meter. The AS10 kinda threw a curve that the static delivered pressure when EPR is ON is several points lower by the 1,2, or 3 setting, than the display pressure. I didn't know this and I had initially thought the calibration was off. Disabling the EPR got the AS10 and the meter to match up.
I now know why the AS10 mask check was giving blowouts on my mask (full face) as its pressure is higher than the DS2. (I'm also hitting close to max pressure and getting blowouts occasionally during sleep on the couple times I used the AS10, but again that's for another thread).
Chart below gives a few numbers I checked on the AS10. The 'Set' number is what was displayed on the AS10 once the it was up to pressure and what the meter read.