March 01, 2006

Bürkert Bypass Mass Flow Meter - Faster and More Accurate For Inntantaneous Process Response

The modular 8701 and 8711 devices, which are available in a variety of materials for different gas characteristics, take gas flow measurement and control to a new level of accuracy with semiconductor sensor arrays built directly into device bypass ventricles.  The units are capable of dual calibration for multiprocess operation.

These capabilities are particularly relevant to food & beverage, environmental and water, waste stream, packaging, laboratory, medical, thin film tech, analyser, heat treatment, industrial laser industries, as well as related industries in which gas flow must be measured and controlled.

"Highest accuracy, longest term stability and responsiveness is the key to generating regular and repeatable process output," said Mr Chris Hoey, Managing Director of Bürkert Fluid Control Systems.

"Bürkert's new mass flow sensor technology has combined the advantages of bypass sensor systems and direct gas flow measurement, allowing extremely fast response to fluctuations in the gas pressure and gas temperature avoiding fluctuation in gas flow and consequently enhancing overall output uniformity," he said.

Bürkert uses a new mass flow sensor technology that, in addition to the actual sensor, integrates analog electronics, linearisation, temperature compensation and analog to digital conversion on one single chip. To achieve this level of functionality, the Bürkert mass flow sensor is operated via a powerful microprocessor that is integrated into the fundamental controls of the devices to directly generate a digital output signal.

Bürkert's Type 8701 measures gas mass flow by diverting a miniscule volume of flowing gas into a bypass channel in which the sensor is located.  Passing over the sensor, gas mass flow is measured according to the thermal principle, which has the advantage of delivering direct mass flow without correction for pressure and temperature.  Flow is read as an analog output, or digitally over RS232- or RS485-communication.

The semiconductor sensor element is a (semiconductor) chip located in the bypass channel.  The sensor part of the chip, produced with CMOS technology, contains a heating resistor and two temperature sensors (thermopiles) which are arranged symmetrically upstream and downstream of the heater. The differential temperature measured by thermopiles is a measure of the mass flow rate passing this bypass channel. The highly accurate 32 point calibration stimulates an unique assignment of the sensor signal to the total flow rate passing the device.  See Figure 1.

Bürkert's new mass flow devices are suited to use in a stand-alone capacity, a modular system component or as a building-block in a comprehensive automation system solution.  Complementary Bürkert technology products add easily to the 8701 and 8711 for complete fluid control solutions.  Recommended modular additions include the Type 1150 Multi-channel programme controller, Type 0330 3/2 or 2/2 way valves, Type 6013 2/2 way valve and MFC mass flow control configuration software (comes free of charge with each device).

"With tighter margins, escalating compliance requirements and pressure for manufacturers to achieve an extremely high degree of uniformity of output, the Bürkert 8701 and 8711 technologies are a timely addition to our range," said Mr Hoey.

With a global network spanning offices in more than 40 countries, and operational outposts in an additional 80, Bürkert Fluid Control Systems is an established and mature global organisation celebrating its 60th Anniversary in 2006. 

Mr Chris Hoey, Managing Director and Regional Coach of Bürkert Fluid Control Systems in Australia, has worked with fluid control and process automation systems for more than twenty years. 

Caption: Sensor array schematic [LEFT].

Caption: Type 8701 and Type 8711 Mass Flow devices from Bürkert Fluid Control Systems [RIGHT].