What difference is there between a regulator flow meter and a regulator flow gauge?
(top) There is essentially no difference as they flow measure flow in standard cubic feet per hour or liters per minute. The regulator flow meter is a pressure regulator with a calibrated flow tube attached to it. The low-pressure side of the regulator is set to match the calibrated inlet pressure of the flow tube. A regulator flow gauge is a pressure regulator with its low pressure gauge calibrated in flow measurements. The regulator flow gauge has a small-calibrated orifice in its outlet.