Litre Meter specialise in the design, manufacture and supply of flowmeters. The unique Pelton wheel based meter design ensures an inherent reliability which has been proven in more than three decades of operation. The VFF rotary piston flowmeter is used throughout the world for chemical flow measurement. Listed below are all the flow meters within our range that are suitable for semiconductor applications; liquid and gas:
Also known as a radial turbine the highly efficient Pelton Wheel meter has some major advantages. The very large blade area compared with the flow inlet port size produces an exceptionally wide range flowmeter which can measure very low flows. The flow through the inlet of the meter is accurately directed onto the rotor which rotates at a speed in linear proportion to the flow rate. A small sensing coil detects the ferrites mounted in the flow meter rotor blade tips as they pass. No drag is imposed on the rotor which assists in the measurement of extremely low flows. Sapphire bearings provide a very low friction mechanically-robust bearing with long life characteristics. Turndown can be as high as 280:1. Ideally suited for low viscosity process liquids measurement up to 2" pipe sizes and larger and up to 10cSt. 0.003 to 500 l/min; ±2.0% of reading (also 1.0%); some models suitable for flow measurement at higher pressure.
The Capillary Thermal principal of operation is based on heat transfer and the first law of thermodynamics. During operation, process gas enters the instrument's flow body and it divides into two flow paths. The vast majority of the gas flow passes through the Laminar Flow Element (LFE) bypass. A very small portion of the total flow is diverted through a small "Capillary" sensor tube with an ID between .007 to .028 inches. This technology is ideal for gas flow measurement and gas flow control. Flowmeter accuracy: ±1% of full scale. From 0.1 to 4 sccm up to 1000 slpm.
The immersible thermal sensor is completely immersed into the flow stream. As a result, immersible thermal mass flow meters measure much higher gas mass flow rates in harsher environments than capillary thermal mass flow meters. There is very little pressure drop across an immersible sensor, and the flow does not have to pass through the LFE as it does with a capillary thermal mass flow sensor. Available from Sierra in either inline flow bodied or insertion flowmeter styles. In-line mass flow meters from 0 to 0.7 nm3/h to 0-20000 nm3/h, +/-1% of reading; insertion flowmeters up to 72", +/- 2% of reading.
Ultrasonic flowmeters measure the travelling times (transit time models) or the frequency shifts (Doppler models) of ultrasonic waves in a pre-configured acoustic field that the flow is passing through to determine the flow velocity. The Sierra range of ultrasonic (transit time) Innovasonic devices are available, click for details. Litre Meter has access to other ranges but the Innovasonic is relatively unique as not only are fixed and portable ultrasonics available but also insertion devices for tougher applications. Ultrasonic flow meters can measure water and other liquids over a range of velocities and with a certain amount of solid content. 25mm to 10000mm;±1.0% of reading (also 0.5%); 0 to ±40 ft/s (0 to ±12 m/s).
Inline 'axial' turbine flowmeters are velocity measuring devices - they measure the average velocity of a fluid flowing through the body of the meter. Mounted within the body of a gas turbine flowmeter is a vaned rotor. The rotor is centred on a shaft and allowed to rotate on bearings. The shaft is supported in the housing by tube bundles that also provide a measure of flow conditioning for the fluid stream. Good for gas flow metering particularly at higher pressures. Wide size range and excellent accuracy. 0.15 to 3.5 up to 200 to 12,000 ACFM. ±1% reading - typical. ±0.25% repeatability. Also good for water flow metering. Wide size range and excellent accuracy. 0.24-17 up to 3028-56775 litres/min. Overrange 150% intermittent. ±0.25% reading - typical. ±0.1% repeatability.