Precision flowmeter - industrial.
Date of manufacture:
This is a precision, industrial quality tube. Oxygen 0 - 300 ml/minute at 15°C, 760 mm Hg. A needle flow control valve is included.
The principle of the device is that a bobbin is suspended in the gas flow to be measured in a tapered glass column. The weight of the bobbin is supported by the rising column of fluid (in this case oxygen). The height to which the bobbin rises is dependent upon the air flow. As the bobbin rises, the gap between it and the wall of the tube increases, permitting more gas to flow past. The contour of the tube dictates the linearity of its flow calibration. While a spherical bobbin offers reliable performance, reading the flow at its maximum diameter is an imprecise art. The Rotameter company have therefore emphasised precise shapes that have flutes causing the bobbin to spin, revealing its freedom to move and providing a clear top edge from which readings can be made with repeatability.
The disadvantage of this type of meter is that, in order to retain accuracy, the device has to be precisely vertical.
The first variable area (VA) meter with rotating float was invented by Karl Kueppers in 1908.