About devices

About devices

Fluid flow sensors

Thermal based gas flow sensor

The principle of thermal based gas flow sensor is presented in Fig. 1a. The device consists of two suspended in a gas channel bridges. The temperature sensor (e.g. thermistor) and a heating component (resistor) are integrated with the second bridge “Bridge 2”. The temperature of the bridge is increased by supplying fixed electrical power to the heater and bridge temperature is measured by the temperature sensor. In case of occurrence of gas flow through the channel the temperature of the bridge is decrease and based “Bridge 2” temperature measurement the gas flow is measured. The additional temperature sensor is integrated with the “Bride 1”. The temperature measurement of this bridge is used to compensate the gas flow temperature variation onto gas flow measurement. Microelectronic three component thermal gas flow sensor is presented in Fig. 1b. The device was fabricated using LTCC technology and consists of two gas terminations (inlet, outlet) and 6 electric terminations (resistor and two thermistors). Resistors and thermistors were deposited using screen-printing method between two 50 µm thick ceramic tapes and are electrically isolated by these tapes from the fluid in the channel.  This make the sensor suitable to measure various fluids.

a)

 Three element gas flow sensor working principle

b) Three component fluid flow sensor

Fig. 1. Thermal based gas flow sensor, a) working principle, b) fabricated device [1,2]

Accelerometers

Piezoelectric accelerometer

The piezoelectric accelerometer is using piezoelectric effect to measure the acceleration changes. It is very important to stress that most of such sensors are not suitable for measuring of static accelerations. However, using special configuration of sensing components make such measurements also possible.  The principle of simple piezoelectric accelerometer is presented in Fig. 2a.Such sensor has to consists of seismic mass and piezoelectric sensing components.  The acceleration in the perpendicular direction to the sensor top surface force to seismic mas to go up and down (no static acceleration e.g. vibrations). This deforms the membrane which is used to suspend seismic mass between sensor frame. This deformation is measured using piezoelectric rings placed in the regions with the highest deformation as in Fig.2a. The simple uniaxial microelectronic accelerometer which utilize piezoelectric effect is presented in Fig. 2b. This device is uniaxial so it can be used only for perpendicular to the top sensor surface acceleration measurements.

a) Piezoelectric accelerometer working principle b) Piezoelectric accelerometer

Fig. 2. Piezoelectric accelerometer, a) working principle, b) fabricated device [1,3]

Wireless communication devices

Low Temperature Co-fired Ceramics (LTCC) was initially developed for the fabrication of multilayer electronic boards. Other words it can be said that LTCC is some sort of alternative to standard PCBs. Hence, LTCC technology is used in the fabrication of wireless communication devices. Electronic boards of such devices can consist: electrical wirings, integrated thick-film buried and surface resistors, capacitors or inductors as well as integrated thick-film antennas. Exemplary devices are presented in Fig. 3.
wireless communication device

Fig. 3. Wireless LTCC board based communication device

References

  1. Jurków, D. (2013). Technology and properties of integrated LTCC sensors. In: J. Kacprzyk (ed.) Innowacyjne rozwiązania w obszarze automatyki, robotyki i pomiarów. Warsaw (Poland), PIAP 2013, pp. 9-18.
  2. Jurkow, D., Malecha, K. & Golonka, L. (2009). Three element gas flow sensor integrated with Low Temperature Cofired Ceramic (LTCC) Module, 16th International Conference Mixed Design of Integrated Circuits and Systems (MIXDES 2009), 493-496.
  3. Jurków, D., Dąbrowski, A., Golonka, L., & Zawada, T. (2013). Preliminary Model and Technology of Piezoelectric Low Temperature Co‐fired Ceramic (LTCC) Uniaxial Accelerometer. International Journal of Applied Ceramic Technology, 10(3), 395-404.DOI:10.1111/ijac.12033 (link to Journal webpage)