Flow Control, Flow Control May 2017

high precision high reproducibility of miniature three dimensional microstructures BMC sensors utilize single crystalline silicon as the sensing material Silicon is among the best materials in the world for highly reliable long term sensors and actuators because of its excellent mechanical properties For long term applications with high reliability requirements the most important advantage of silicon is that it is a crystalline material and stays elastic until it breaks without plastic deformation A metal tube or diaphragm will plastically deform over time when exposed to creep and fatigue factors This results in performance drift which is a liability If a silicon structure is bent it either goes back to its original position or breaks but never deforms As a result silicon sensors could be practically free of fatigue hysteresis and drift Therefore BMC products provide advantages for demanding high cycling applications such as resonating tubes that face billions of vibration cycles System While the MEMS device level features are important a more important advantage of the MEMS technology is in the systems integration One of the most important contributions of BMC disruptive technology is that the entire mechanical Coriolis fluidic sensing system is integrated into a single microchip that requires only low voltage electronics for its full operation The system includes resonating flow tubes flow in out ports and low voltage electronics circuits for its entire operation tube vibration sensing tube frequency density sensing tube twist mass flow and sensing fluid temperature viscosity Balanced sensor BMC products utilize a balanced vibrating tube sensing technology versus unbalanced vibrating tube When an unbalanced Coriolis tube resonates it creates an equal and opposite force to the substrates on which it is mounted which places limitations on its packaging and installation BMC sensors use a balanced structure with lightweight tubes resulting in no inserted force as well as lack of sensitivity to the sensor package and masks the installation substrate from the sensor vibration The balanced structure overcomes major practical problems the most important of which are the ability to operate without requiring a mass from or having any dependency on the overall sensor package and compatibility with a variety of assembly techniques The balanced structure is impervious to stress from the sensor package installation or other sources and it is resistant to temperature changes of ambient sensed fluid package and installation substrate The structure is unaffected by the installation environment and any crosstalk and therefore multiple BMC sensors can be installed side by side End user priorities are stability accuracy resolution speed initial cost and cost of ownership which the new technology supports with several features Imperviousness to ambient noise vibration Stainless steel tube Coriolis sensors are vulnerable to environmental vibrations since the resonant frequency of their tube is low 1000 Hz BMC microtube resonant frequency is high 20 kilohertz because of several parameters including small size silicon superior physical properties and microtubes light weights Reliable against shock Because of light weight of the microtubes micrograms Low fluid dead volume The small size of the microtube microliters creates orders of magnitude with lower dead volume than the tubes Rapid fluidic measurement response density viscosity temperature flow High resonant frequency results in a fast response to fluids properties can be 1 millisecond Low dead volume of the tube microliter results in fast fluidic step response Rapid and accurate fluid temperature measurements caused by small mass embedded temperature sensor and silicons high heat conductivity High resolution repeatability and accuracy in real time Because of high resonant frequency high quality factor balancedtube measurement technique low silicon density silicons properties imperviousness to environmental parameters and high performance electronics Resolution of 5X10 7 gram cc in real time with flow through the sensor High reliability and stability Silicon properties and lack of plastic deformation stage Operation is based on electronics no magnetic vibration or laser detection Custom electronics further compensate many secondary parameters and the potential for failure and drift caused by these electronics mechanisms is extremely low MEMS devices Attributes of silicon material for MEMS devices include Mechanical properties Precision submicron micromachining Batch fabrication Extensive technology base Low cost and high quality of supplies of silicon wafers Potential for corrosionresistant applications Image 2 A BMC MEMS sensor on a penny on a fingertip www flowcontrolnetwork com May 2017 17