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Número de pieza | AN884 | |
Descripción | Miniature Flow Sensor Has Electronic Temperature Compensation | |
Fabricantes | Maxim Integrated Products | |
Logotipo | ||
Hay una vista previa y un enlace de descarga de AN884 (archivo pdf) en la parte inferior de esta página. Total 6 Páginas | ||
No Preview Available ! SENSOR SIGNAL CONDITIONERS
Application Note 884: Dec 13, 2001
Miniature Flow Sensor Has Electronic Temperature Compensation
Fluid analysis is essential in a wide range of current applications. Biology, medical
analysis, genetic engineering, and many other fields rely on fast, precise, and
reproducible chemical and biological analyses. Tools that automate the dosing and
analysis of fluid samples are essential for affordable performance.
Highly specialized electronic sensors have been designed to automate sample analysis, but the
dosing of liquids – still a prominent issue – must be done physically. This operation is usually
accomplished with specialized micro-syringes driven by stepper motors. It's easy to imagine the
difficulty and expense associated with such setups.
In a novel approach to this problem, DASA IMT and Seyonic SA (both of Neuchâtel,
Switzerland) developed flow-through micro-fluidic dosing as part of a toolkit for experiments
performed in space. As described in the following, a key element of that design was a micro-
flow sensor device. Requirements were:
• Small size
• Chemical inertia
• Temperature stability
• Long-term stability
• Simple, easy, and fully automated recalibration
• Linear voltage-versus-pressure output
One way to measure micro-fluidic flow is by measuring the pressure difference across a
restriction integrated into a micro-flow channel. Pressure measurements are performed with
dual piezo-resistive pressure sensors, one placed before the restriction and the other behind.
To insure that the sensor is not affected or altered by chemically aggressive fluids, the fluid
under pressure is applied to the back of the sensor diaphragm (whose monocrystal-line silicon
is relatively insensitive to the chemicals) rather than the front. This unusual configuration
protects sensitive microelectronic circuits on top of the sensor by shielding them from the
liquid. To prevent error from mechanical-tension forces, the sensor is mounted on a thick
ceramic substrate (Figure 1).
www.maxim-ic.com/an884
Page 1 of 6
1 page Figure 4. The pressure-sensor module consists of a dual flow sensor and two signal-
conditioner ICs.
A photo of the 12x19mm pressure-sensing module (Figure 5) illustrates the MCM technology:
a monolithic flow sensor module, wire-bonded to the ceramic carrier, connects to the two
sensor-signal processors (MAX1458s), which are also wire-bonded and mounted as dice.
Figure 6 illustrates a micro-fluidic dosing and analysis system, in which the flow-sensor output
described above serves as a feedback signal in achieving continuous and dynamic flow-rate
control.
www.maxim-ic.com/an884
Page 5 of 6
5 Page |
Páginas | Total 6 Páginas | |
PDF Descargar | [ Datasheet AN884.PDF ] |
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