CNBTR LZQ-3 Acylic Flowmeter Gas Acrylic Metal Fitting Oxygen Flow Meter 0-5 LPM

Q: what can be done to get accurate readings? the one i received is 35% low. 4lpm reads 2.5lpm. this is no mistake as i checked it with 4 sources.

Throw it away and buy something more substantial. These are junk.

Q: Are the connectors the correct size to use with medical 02 flared female ends of canula & long line?

it is a 1/4 fitting on the flow meter. O2 hose is about an 1/8 inch so it is a tight squeeze. Best bet is to get a plastic reducer coupling available on Amazon.com. Get a 1/4 by 1/8 barb reducer and go to you local hardware store and get a 1 foot length of some 1/4 ID clear tubing and couple it that way. You can use small zip ties as hose clamps if you need to.

Q: Can this regulate to a 1L/m flow from a gas cannister that has 2000psia?

No would not be safe. you would have to incorporate a pressure regulator between the 2000 PSI and the plastic flow meter. refer the manufacture for the maximum pressure rating.