DE1903038A1 - Resistance element for devices for determining physical quantities - Google Patents

Description

: Dip! - lng. ERICH E. WALTHER

Pcicntcnwcit

Applicant: N.V. PHILIPS 'GlOEiUMPENFABRlEKE * FHIT. 2? Ο.ρ.

File: PHN- 2990 _Kt "/ _Hjy , Application dated Jan. 21, 1969 *

"Resistance element for devices for determining physical oases".

It is known that different physically equal sizes

aen can be determined with the aid of devices in which electrical resistance elements are arranged in such a way that the value or the change in value of the resistance is a measure for the value or the change in value of a physical quantity. . '

Sometimes the "translation" of the values becomes more physical The temperature sensitivity is expressed in resistance values used by resistance ducks. This is 2.B, the case with devices for moaaen of gas pressures (Journ. Sei. Instr., 1965) Volume 42, 3 # iit 342), of temperatures and flow velocities of oases and liquids, and of changes or rapid fluctuations between them Oröaen. Furthermore, e.g. the temperature sensitivity of resistance - *

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PHH. 2990.

elements in bolometers for measuring electromagnetic radiation; at Apparatus for performing qaaohromatography and devices for flame monitoring and for regulating the liquid level »btntitst will. Which occurs as a result of a changing temperature In all these cases, a jiaaa for di · au ermitt «!» «» the physical quantities.

In other cases the occurrence of a change in the resistance values as a result of a reversible mechanical deformation of the elements under the action of pressure, tension, bending or torsion is used. This I3T the case with strain gauges, scales eltktromeohanischen, microphones and devices AUEM measuring high QAS ¹ and liquid pressures at which the Wideratandaelemente be verfomri. Even with these devices, which einstallend "resistance gtets a Maas to be determined physikalisohtOrofsst" is -> .- "The vorerwaluiten devices ee usually more" kind, that the resistance elements a high sensitivity, a rate · response time and a high degree of _stability? under the conditions to which they are exposed, “In those cases where the elements are exposed to very high and very low temperatures Mexäetif dia, requirement must be added that the sensitivity, the aaspa? e6h” and the stability in a wide tea apparatus ®r®ioh

Hit Hückaioht on the reasonable sensitivity \> ■ '^;; i ^:

· ■■ ■ '\ - ■. '- ^: ' ■■ ■ - ^;

because (s required response behavior is necessary, "" dag® etilr "& © *>". ■ / {.

matching resistance elements © ine low j! aesφ habas ün & that _; · Ί hg® length large in relation to sur ^ Diijke is «- Di © iÜBg © wxbu mlnümim® m>n," be on the order of millimeters, so that the üontßg® and di® An «=

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electrical contacts are feasible and at the same time a sufficient, without a large effective part of the element is retained.

. A disadvantage of resistance elements made of metal wires and polycrystalline semiconductor materials mostly obtained by ceramic means, which is used to determine physical quantities are 5 1st their low mechanical strength with the small dimensions favorable for these applications.

An improvement in this regard are the resistor elements made of silicon carbide monocrystals, the Vor suggested a few years ago for some of the purposes mentioned sihd (Journ. Sci. Instr. 1965, vol. 42, p. 342). This resistance » elements meet several of the above requirements and are also very resistant to high temperatures and corrosive media «

These well-known elements are made from large single crystals obtained by mechanical processing such as sawing and grinding. As a result, it is difficult to use a large number of these elements in a geometry required for the various applicationsj i.e. in the form of thin wire-shaped bodies.

The invention relates to a resistance element for devices for determining physical quantities in which ^ this Element is arranged in such a way that the "occurring value or the Fourth change in resistance is a measure of the value or the change in value of a physical quantity, and it is therefore noticeable * shows that the element consists of a SiIiziuB carbide crystal grown in the form of a wire (SiIiziumoarbidhaarV: crystal) with at least a length

consists in the size of the millimeter,.

Under wire-shaped crystals (or whiskers)

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are elongated crystals with any cross-section understand eu ». '"

_a . The resistance elements according to the invention have the aforementioned disadvantages of known resistors that are used for the relevant

- Devices have not found application on. They are chemically resistant, withstand high! Temperatures and trots are overall their

■ dimensions mechanically tight. They can also be sold in large ■■ r sen numbers in the favorable geometry with the required length and produce the desired resistance properties.

j. ----- ^ Me ^ mentioned wire-shaped silicon oarbldkrietalle (Siliaiumoarbidhaarkriatalle); can like this in German

Patent Application -, F-16 67.65544Ii. ·; ■;. ■? .. '.:.' vorgesohlagen is ^ on one. , \. - -

• ways be obtained in large numbers in the right dimensions by recrystallization and / or condensation ift _v a limited by Silisiumcarbid space in a protective gas atmosphere at temperatures of about £ 500 ° C in the presence of lanthanum. It is also possible, as stated in the detailed patent application / P. 16. 6.7. 65Τ · δ '■■ "■> [λ has been forgotten, such silicon carbide crystals by VLS (vapqur-liquid-BOlId) -WaOhStUm with iron as the liquid phase from a silicon and carbon-containing gas phase at temperatures between about 1200 ° 0 and 1600 ^e To form C «

As mentioned in the two patent applications mentioned is; can with or na oh the growth in the crystals substances sum Ξτ °°

- Obtaining the desired characteristics of the Leltuagea in the correct dosage

to be built in" - .

■ '. ■; ■; .. ■ Sia ti older advantage dos ?, from wire-shaped grown > Silieiuaoarbldteistallen (Silisltimea ^ lahaa ^ crystals) existing

PES. 2990.

Resistance elements compared to the known elements produced by mechanical processing from large single crystals is that they are available in smaller thicknesses and that the; mechanical Strength is not affected by surface damage. There is also the fact that they are available in greater lengths, which also makes the known fact can be used that made of silicon carbide existing bodies can be melted directly into hard glasses such as borosilicate glasses. -. '

The invention is explained in more detail below by means of a few exemplary embodiments with reference to the accompanying drawing. Example 1, *

In a space limited by silicon carbide

at 255O ⁰ C by recrystallization and / or condensation in the vapor of lanthanum oxide and aluminum carbide in an argon atmosphere, p-type band-shaped silicon carbide crystals (strip-shaped silicon carbide whiskers) are grown.

One of the obtained crystals with a width of

Is μπι 150 microns and a thickness of 30 to 30 by solid Intern \ ira strong tungsten wires which are heated au this purpose by current passage, versähen with ohmic contacts. With a length of 10 mm between the contact wires, the crystal has a resistance of 50 ΚΛ at 20 ° G.

As shown schematically in Fig. 1 of the drawing, this is made from the wire-shaped, grown silicon carbide crystal (Silicon carbide whisker) 1 existing resistor element with the Tungsten contact wires 2 in an Olas-

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190 ¥ Ö38 ^r

2990

piston 3 melted down. - \ v

The: ■ current-voltage characteristics of the element! will

measured in air at different pressures. The characteristic curves for the pressure of 76 ^ 0 and 5 · 10 Torr are shown in the diagram of FIG. 2 in logaritiiiaisiöieii Maastali duroK 5 and 6 , respectively. -

From this figure, it appears that increases and at a constant voltage of 1Ö Volt.der current in the mentioned pressure range by a factor * 9 that thus recording in ain · Bruckenaohaltuhg, after calibration, with the element very accurate Gasdruokmessungen can be performed duroh.
Example 2. ·

As shown schematically in FIG. 3, an anemometer is produced by inserting into a borehole 11 made of borosilicate Glass with an inner diameter of 5 "ηκι a wire-shaped grown

Silicon carbide crystal (silicon carbide whisker crystal) 12 mossed in -. is. '-_ ■. ·.

k The crystal 12 is ^ on one of those naoh example

1 grown in a similar manner, with boron chloride being present instead of the aluminum compound to adjust the line properties.

The crystal consists of silicon carbide, which is p-conductive due to a 3ordoping, has a width of 150 μιη and a thickness of 30 ^ m and is at the ends outside the tube 11 with the help of an alloy of gold with 2 $ tantalum and 1Q / & Aluminum provided with ohmic contacts 13. The resistance is at a loop of 6 rom. ■ between the contacts 72 kjfi at 20 ° C «

The resistance element is in a Wheatstone JJruOk « recorded, whereby a voltmeter with an input

r: 909835/1042

. . PHU. 299O.

- 7 ■ - ■ ■ '. ■■ _ :,'. - '' ■■:; ■:

ton about i ΗΠ is used «In the bridge are further

Of the same order of magnitude as silicon carbide *

crystal mijfgenpramen «

When through the glass tube 11 a minute air flow

"tarn ID ml Hh & urohleitung is, the voltmeter indicates at a di ·" Brück «applied voltage of 170 VoIf a deflection tron 0.7 ToIt.

It turns out that the anemometer is ready in the case of bitter, minute-long strangeness de "Q ^ aee tone only. in the direction of Kl, so that after calibration it was ready for measurement Gasstroaen Henutat become Kanha

Because, as is well known, the rash of the voltti ...

de "you are dependent on" uaeee "kattn di *

, t, direction offensiahtiioh without further ado in an apparatus for G * sohro »ato-

find gritphie border.

B »iapiel 3» :

For measuring rapidly fluctuating gas temperatures in A resistance element is used in a Heisagasn motor, which is a silicon carbide crystals grown in the form of p-conducting wire-shaped through a 3ordoping (SilifeiüooarbidhaarkriBtall) consists «

The crystal is made by VLS-Tiachstu »with iron as

Liquid Phftae from a Silicon and Carbon Containing Kasserii |: 4 "JP Ο ^ ίΓοΙ · / »SäAörftn (BgB ^) iugesetzt l * i, received«

Jier -iG? Ist * ll has a linen Duröhmesstr of 5 μ «and- ei» e- ^! .- .- - ^: -

" ⁰ 200 'JI ^ / and at 700 ° - ^: ; ^: ';

31 »the with Ktlfe vifoa tm && ^^

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PHN. 2990. '- 8 -

and aluminum is provided with ohmic contacts at the ends Contact wires 32 made of chrome-nickel steel attached. These are with Help τοη! Feedthroughs 33 arranged in a plate 34. The whole is in a bore 35 in the cylinder wall 36 of a hot gas engine attached.

Bas resistance element that is suitable for multiple temperatures is calibrated, is inserted into a bridge holding. In the event of a temperature change, the bridge is lifted out of the bond due to the change in resistance that occurs as a result. The resulting Fluctuations in the diagonal voltage of the bridge are observed with a cathode ray scanner "

The temperature of the oasis · In the cylinder of the engine at the Still · des Wideretiandseleaenies can change abruptly »You changes are in the order of magnitude Ton 10 $ of the mean absolute temperature dta Qaee «and ei · form a periodic function, the base frequency of which corresponds to the minute rotation τοη e.g. 1500 of the Kotore.

The resistance element differs advantageously from the resistance elements made of metal wire that are customary for the Zveok in that, with greater mechanical strength, it has a higher hiding value for the measurement of temperature fluctuations due to changes in resistance. Example 4,

A band-shaped silicon oxide crystal (strip-shaped silicon carbide hair crystal), which has been obtained in the world shown in Example 2 and has a width of 150 μm , a thickness of 30 μm and a length of 7 am, will be a bit too good

j, The resistance is 85 k & Mi SD ° O ₄ 909835/1042

PHN. 2990. - 9 - '

This resistor element is in series with a resistor with the same resistance value to a stabilized voltage source connected. The crystal is placed close to the exit slit of a mono-tube. The one that changes due to incident radiation Resistance of the crystal is measured as a change in voltage. With the help of these voltage changes, after calibration of the element, the relative intensity of the radiation emerging from a monochromator can be measured as a puncture of the frequency.

When the measurement is carried out, this is carried out by a in front of the entrance of the Monoehromators arranged light source aerrührende Radiation interrupted with a sequence of 30 Hz. The voltage changes across the resistive element are shown as a function of the wavelength of the emerging light is detected by amplifying it with an amplifier tuned to 30 Hz, then phase-sensitive can be detected and finally recorded.

The result is shown in the diagram in FIG.

As ordinate the voltage variation Δ V is plotted in arbitrary units and the abscissa are indicated marker points for certain values of the photon energy hv in electron volts.

The curve of FIG. 5 shows the high sensitivity and the short response time de3 temperature-sensitive resistance elements used. It should be noted that the high temperature resistance of the element means that it can also be used with high radiation powers.
^ eJ3piel 5 «

A ribbon-shaped, η-conductive silicon carbide crystal (strip-shaped η-conductive silicon carbide whisker) is

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speaking example 1, with the proviso that instead of one Aluminum doping a nitrogen doping is used.

The crystal 41, which has a width τοη 150 μυι, a Now has a bead of 30 μm and a length of 5, as in Tig « 6 is shown schematically, over from QoId with 1 ^ tantalum taxing ohms before contacts with lead wires 42 welded and in one Two-channel quartz capillary 43 attached «

. The whole thing is in a cryostat 44 with liquid Nitrogen 45 arranged so that the crystal 41 * on a desired height.

A fall in nitrogen, at which the crystal becomes free of the liquid, results in a sudden change in resistance from f5 kn to 100 k £ l, which enables a rapid display of the fall that has occurred.
Example 6 »

A wire-shaped silicon carbide crystal (silicon carbide

\ bidhaarkristall) is produced by VLS-WaOhstun in an atmosphere consisting ^{of hate substance with 0.01 vol. c} / a nitrogen. The crystal has a diameter of 5 μ-si and a length of 10 om.

As shown in Figure 7, this crystal 51 is provided at one end with an ohmic contact 52 and at some distance from the other end with an outer ohmic contact 53.The resistance of the crystal between these two by cathode sputtering of an alloy of gold and Ύ / ο Tantalum manufactured ohmic contacts is 10 ka.

The contact 52 is provided with a lead wire 54 and clamped in a plug 55 which is attached to the top of the

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56 is attached. The other end of the crystals 51 is through. «Ine far lower Ekide of the vessel 56 provided capillary 57 led out Hinduroh,

In dae Gefäes% an alloy 5 & us 75 / "Qalliua and 25 $ indium is added, which is flüesig at room temperature * The Qe * tumn further let a Kontaktdrah't 59 made of tungsten is provided, is, like the contact 53 liquid in the Alloy protrudes

When the element is loaded with a weight of tone 3 g a surge in resistance of 16 / * is measured, which is a consequence dtr during the load the reversible mechanical deformation is «

The sensitivity of the element for measuring forces also increases the usefulness of such resistances. Microphone and strain gauge.

ORIGINAL BATHROOM! - 809835/1042

Claims (8)

PHN. 2990. ~ 12 - PATE IT TAK PROVERBS, 1, resistance element for devices eur investigation physical quantities in which the element is arranged in such a way that the occurring value of the resistance or the resistance change a measure for the value or for the change in value of a physical one Grosee is marked by this! that the element consists of a "Wire-shaped grown silicon carbide crystal with at least one Length in the order of magnitude τοη millimeters « 2. Device for determining physical quantities with a stand element according to Anepruoh 1 «- 3 · Device according to claim 2 for measuring gas pressures · 4 »Device according to claim 2 for determining physical Kalischen Qroseen with application τοη mechanical forces on the resistance element naoh Anepruoh 1 ·
5. Anemometer naoh claim 4. 6. OasChromatograph with an anemometer according to claim. 5 » 7. The device according to Claim 2 to Hesse of temperatures or determination of temperature determinations, 8. Hot gas engine with a device according to claims 7 about the rapidly changing gas temperature 9 » Device according to claim 2 for determining electromagnetic radiation · 909835/104 2