how to Control inflation of balloon

Hello there,
How do inflate a bag with air with a pump to a fixed pressure.
1) required pressure in bag varies from 1mmHg to 100mmHg
2) pressure sensor provides instant readings but is hampered by noise.
3) pumping pressure at 0mmHg is 40mmHg.


My question is what is the way to get the exact required pressure because
when pump is on reaching a pressure of 40 or above. the actual pressure in the bag a far less.
Kindly guide. Thank you.

Pump in bursts, allowing enough settling time between bursts for the pressure sensor to stabilise to an accurate value.

You can measure the rate of change between bursts to get an ideas of how long the pump must run to achieve a particular pressure, then if it's a long way off the target, use a long pump run to get to eg. 90% of the target before stopping and testing again.

That's pretty much how automatic car tyre inflation machines work, if you have ever use one of those - they have the exact same problem that the pressure sensor is near the high pressure air feed, with a long hose between that and the tyre.

You could insert a gauge vibration damper between the pump/balloon and the sensor. It will stabilize the pressure readings. Or as rjenkinegb suggests pump/stop/ measure/repeat. That's how automated blood pressure cuff machines work (in reverse)...bleed/stop/test/repeat.