FI62908C - FOLLOWING AN ORDER WITH MAINTENANCE OF FASHION - Google Patents

Description

1 62908

Method and apparatus for measuring phase change Förfarande och anordning vid mätning av fasändring

The invention relates to a method for measuring a phase change by detecting dew or other similar liquid with a piezoelectric or similar sensor, in which acoustic surface waves are induced and which surface is exposed to condensation or presence of detectable dew or liquid, which is detected by attenuation of acoustic surface wave by.

The invention further relates to a device for measuring phase change, which device comprises a substrate in which a surface wave can propagate and structures necessary for generating and possibly detecting a surface wave on the surface of said substrate, the operation of which is based on piezoelectricity of either the substrate or other attached material. one or more electrode patterns made of 15 conductive materials, through the contacts of which the alternating electric power is supplied and possibly taken out of the sensor.

A method and apparatus for detecting a dew point or the like as defined above is already known from basic application No. 800623, from which this application is separated by cleavage.

The present invention provides a new and advantageous use of the method and apparatus according to the above-mentioned parent application. According to the present invention, the method and apparatus as defined above are used to measure volatility and / or compaction rate. The method and device according to the invention can be used, for example, in agriculture or meteorology, where it is often necessary to measure the evaporating effect of environmental conditions.

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The method and device according to the invention achieve several advantages, the most important of which are the small size of the device, the fact that the dew point can be measured simultaneously and the fact that the device is independent of external liquid stores.

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In the following, the invention will be described in detail with reference to some application examples of the invention shown in the figures of the accompanying drawing, to which the invention is not limited.

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Figure 1 schematically shows a device combination applying the method according to the invention.

Figure 2 shows an embodiment of the surface pattern of a surface wave converter.

Figure 3 shows a partial section III-III in Figure 1.

According to Fig. 1, the piezoelectric substrate 10 is provided on the transmitter side 15, e.g. is shown in Figure 2, according to which the electrodes 20 12 and 13 are connected in pairs by interleaved bands 12 'and 13'. The distance between the bands 12 ', 13' in the propagation direction A of the surface acoustic wave is denoted by: 11a. According to Fig. 3, the finger patterns 11,14 are protected by e.g. S1O2 with a protective layer 17 having a thickness of 1000 ... 3000 Å. The substrate 10 is, for example, 0.5 mm thick LiNbO 2.

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Figure 1 is a side sormikuvioinnin transmitter 11 and the reception-side 14 of the distance between the sormikuvioinnin denoted by b. In this region, as well as in the region of the finger patterns 11 and 14, the attenuation of the surface acoustic wave (SAW) 30 propagating from the transmitter side (impedance Z. ^) to the receiving side (impedance Z t) occurs.

According to Fig. 1, electrical power of about 100 ... 200 MHz is supplied from the RF generator 20 to the finger patterning between the electrodes 12 and 13, for example. Thus generated in the piezoelectric substrate October 35 acoustic vibrations that propagate to the receiving side and there arises sähkövärähtely with similar frequency based on piezoelectric phenomena between the electrodes 15 and 16, which are detected devices method 30 of the invention is based on e.g. surface acoustic 3 62 908 wave (SAW) filter attenuation of the transmitter side 11 and a receiving side 14 of the route. The magnitude of this damping depends quite strongly on whether water or other liquid has condensed on the surface 18 of the layer 17 and how much there is on the surface 18. As said 5, the substrate 10 is a piezoelectric material e.g. quartz, lithium niobate or the like. The mutual distance a of the finger patterns 12 ', 13' depends on the length λ of the acoustic surface wave excited by the electrical frequency f, e.g. as follows: 10 a = λ / 4; 3λ / 4; 5λ / 4; 7λ / 4 etc.

When the surface 18 is cooled in a clear manner, dew begins to form when the relative humidity RH (T)

T

15 RH (T) = exp {B [i + i] + C log [^]}, and B = 6704.48 C = -4.71784

T = ambient air temperature K

20 Tq = dew point temperature reaches 1. Then the surface temperature is Tq. When Tq and T are known, RH (T) is obtained from the above equation.

25 the described operation of the device quantitatively can be described so that the substrate 10 temperature after close to the dew-point temperature Tq from 10 on the surface of the substrate 18 to condense the water or other fluid, which is detected by the output-side 11 and the receiving side of the acoustic between the 14 surface-wave attenuation increase 30 of the electronics unit 30 . In this case, by measuring the temperature Tq and the ambient temperature T, the relative humidity (RH) can also be determined, if necessary, and displayed directly with the pointing device 40, if necessary.

The above method and / or apparatus is used in accordance with the present invention to monitor the amount of condensed liquid over time. Thus, the device described above is arranged to act as a measure of the rate of volatility and / or compaction. From the above, the electronics associated with the device will be apparent to one skilled in the art.

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In this context, volatility refers to the mass of water leaving a unit-sized surface in a unit of time. It is a complex function of ambient air temperature, relative humidity, and flow rate. It is often desired to measure the evaporative effect of environmental conditions 5 in, for example, agriculture and meteorology.

The operation of the volatility measuring device according to the invention is as follows: - The surface 18 is cooled below the dew point. Water condenses in the surface acoustic wave (SAW) path.

- The appliance is warmed up to ambient temperature. From surface 18 water begins to evaporate and the surface wave attenuation is small.

15 - Measure the time taken for the wave attenuation to decrease from a certain set value A ^ to another set value A2 · There is an unambiguous relationship between the measured time and the volatility, which can best be determined experimentally.

The following claims set out within the scope of the inventive concept defined by the various details of the invention.

Claims (3)

5 62908 A method for measuring a phase change by detecting dew or other similar liquid with a piezoelectric or similar sensor in which acoustic surface waves (SAW) are applied to an associated surface (18) and which surface (18) is exposed to condensation or presence of aeration dew 5 or liquid, which is detected based on the measurement of a surface acoustic wave (SAW) attenuation parameter, characterized in that the method is used to measure the evaporation and / or compaction rate. Use according to claim 1, characterized in that said surface (18) is cooled below the dew point so that water condenses in the path of the surface acoustic wave (SAW), said surface is heated to ambient temperature so that water begins to evaporate and the attenuation of the wave (SAW) begins to decrease, to measure the time elapsed when the attenuation of the wave decreases from a certain set value to another set value, and to determine the volatility on the basis of said unambiguous dependence between said measured time and the volatility to be measured. A device for measuring phase change, the device comprising a substrate (10; 10 ') in which a surface wave (SAW) can propagate and structures for generating and possibly detecting a surface wave on the surface of said substrate (10; 10'), the operation of which is based on piezoelectricity of either the substrate (10) or other material attached thereto, the structures comprising one or more electrode patterns (11,12,13,14,15) made of a conductive material, through the contacts of which alternating electric power is fed and possibly taken out of the sensor, characterized in that that the device is adapted to measure volatility and / or compaction rate. 62908 6