When talking about small lines and low flow rates gas and liquid flow measurement,ultra low flow meter,we have some reliable recommendations, such as mini thermal mass flow meters, ultra low flow liquid turbine flow meter, metal tube Rotameter. See below general introductions for the rugged ultra low flow meters also at low price cost.

Low flow mag meters can handle liquid flow as low as to 330 ml/min (min flow rate 0.09GPM), the mini mag flow sensor size we can provide is 1/8”,1/4”,3/8”,1/2”,3/4”. Micro flow magnetic flow meters are used widely in chemical or fertilizer injection industries.it can measure strong aggressive and corrosive liquid, such as HCL, H₂SO₄, caustic soda, Phosphoric acid, hydrofluoric acid (HF acid),nitric acid.,etc, however it can also measure water, it is a kind of micro water flow meter.

Low flow gas flow meter employs the thermal dispersion principle whereby the rate of heat absorbed by a gas or air flowing in a closed pipe or duct is directly proportional to its mass flow passing.It is a kind of low flow mass flow meter for gas or air. Product Link: https://www.silverinstruments.com/application/low-flow-flow-meter.html