Graduated cylinders Electronic Timer. Manufactured by Dimco-Gray Co., Centerville, Ohio. These buttons control and regulate the flow of water through the system. Clicking either button will adjust the flow in incremental steps whereas depressing either button will adjust the flow continuously. The push button flow regulators visible on the screen actually replace a needle valve built into the bottom of the flow meter.
Water is supplied to the back of the flow meter from an elevated storage tank.
For clarity, your diagram of the equipment should have the needle valve represented separately in series with the flowmeter. This valve switches the flow of water from off to fully on at the maximum flow rate possible through the system. Flowmeter A class of flowmeters, called area meters, consist of devices in which the pressure drop across the instrument is constant, or nearly so, and the area through which the fluid flows varies with flowrate. The area is related, through proper calibration, to the flowrate. The most important area meter is the rotameter.