Active solid-state devices (e.g. – transistors – solid-state diode – Test or calibration structure
Reexamination Certificate
1998-12-22
2001-05-15
Pham, Long (Department: 2823)
Active solid-state devices (e.g., transistors, solid-state diode
Test or calibration structure
C374S171000, C374S185000, C216S016000, C438S014000
Reexamination Certificate
active
06232618
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention involves a sensor having a temperature-dependent measuring resistance (resistor), that is connected by a connection contact to an evaluation circuit and is flowed through by an impressed current, wherein a voltage signal dropping across the measuring resistor is determined, which relates to its temperature in an at least approximately linear proportional manner, wherein the measuring resistor is electrically connected at one end both with a constant current source as well as with an electrical circuit in order to output a temperature-voltage signal, while a connection point of a series connection made of the measuring resistor and a reference resistance is connected to the electrical circuit. The invention also relates to a use of the sensor in an electrical circuit for temperature measurement.
From U.S. Pat. No. 3,613,454 a device is known for temperature measurement using a temperature-sensitive measuring resistor that is flowed through by an impressed current, wherein the voltage generated on the measuring resistor is supplied as an input signal to a differential amplifier, whose output forms a voltage output signal that is at least approximately linearly proportional to the measuring resistor temperature. For this purpose, the impressed current is supplied from the output of a first differential amplifier to the measuring resistor connected to the input of a second differential amplifier, such that the current flows through a reference resistor that is connected to it in series, whose voltage is supplied as a signal for inverse feedback to the input of the first differential amplifier for the purpose of stabilizing the impressed current.
It proves to be problematic that the construction of temperature sensors using wound platinum wire is relatively expensive.
Furthermore, from published German patent application DE 24 60 648 A1, a circuit arrangement is known for measuring temperature using a platinum resistance thermometer in linear relation to the output voltage, wherein as a function of a reference voltage, a differential amplifier impresses onto the platinum resistance, acting as a temperature sensor, a current that remains constant with the value of the platinum resistance, so that the voltage on the platinum resistance increases linearly with the temperature. In this way, using a suitably dimensioned differential amplifier, a voltage is generated against the reference voltage in such a way that the voltage offset for the initial temperature of a given temperature range disappears. For larger currents through the platinum resistance, the intrinsic heating can be reduced by an impulse sequence with the amplitude of the input voltage.
For temperature equalization of ovens, the desired temperature level of a temperature regulator is linearly preset as a voltage value. The desired voltage value can be obtained from the reference voltage using a potentiometer circuit; furthermore, the desired voltage value can also be preset by a digital-analog converter. This involves a relatively expensive arrangement for operating several ovens, wherein the respective components such as the comparator, digital memory, platinum thermometer, digital-analog converter, and progress control form their own respective circuit arrangements.
Furthermore, from published German patent application DT 22 08 852, a circuit arrangement is known for generating a linear temperature-dependent electric quantity using a resistor bridge circuit, wherein one of the bridge resistors is constructed as a platinum measuring resistor; the bridge diagonal being formed by a differential amplifier. In particular, the linearity of the platinum sensor is obtained by an inverse feedback effect that exceeds the positive feedback; the positive feedback thereby linearizes the output signal in reference to the temperature characteristic, whereby the inverse feedback prevents a tendency to oscillate.
This thus involves a circuit arrangement having many electronic components that is technically and spatially relatively expensive.
SUMMARY OF THE INVENTION
An object of the present invention is to construct a highly sensitive temperature sensor that has a small, compact construction and can be used up to a temperature of approximately 300° C.
This object of the invention is achieved according to a device in which the temperature-dependent measuring resistor and the reference resistor are each arranged as discrete structural components on a substrate having an electrically insulating surface, wherein the connection-contact banks for the measuring resistor and the connection contact banks for the reference resistor are each connected via strip conductors or wire connections to an evaluation circuit also arranged on the substrate in a micro-module.
This means that the impressed current flows through a series circuit formed by the measuring resistor and a reference resistor, wherein the potential of the connection point of both resistors is compared to a potential that is preset by the associated voltage supply on the input of a first feedback differential amplifier, wherein the potential applied at the output of the first differential amplifier is formed as a function of the temperature of the connected measuring resistor and is conducted further onto the P-input of an after-connected second differential amplifier in a subtracting circuit, wherein the output of the second differential amplifier yields a potential corresponding at least approximately to the temperature at the measuring resistor.
Also proving to be especially advantageous, along with the rapid responsiveness, is the high degree of amplification of the temperature signal values and the relatively small construction size, so that a sensor of this type can also be retrofit in already existing systems without particular problems.
In an advantageous embodiment both the measuring resistor and the reference resistor are each constructed as separate structural components, wherein the remaining part of the evaluation circuit is integrated in at least one micro-module. Herein, the P-input of the first differential amplifier is connected via the middle tap of a voltage distributor, made out of two resistors, to the binding posts of a direct-current supply, and the measuring resistor connected to the output of the first differential amplifier is connected in series with a reference resistor, wherein the connection point of both resistors is connected directly to the N-input of the first differential amplifier, while the output of the first differential amplifier is in addition connected to the P-input of an after-connected second differential amplifier in subtracting connection, wherein on the output of the second differential amplifier a voltage signal is applied that is proportional to the temperature on the measuring resistor.
It proves to be advantageous that the temperature-dependent measuring resistor and the reference resistor are each arranged as discrete structural components on one substrate with an electrically insulating surface, wherein the connection contact banks for the measuring resistor and the connection contact banks for the reference resistor are each connected via strip conductors or wire connections to the micro-module that is also arranged on the substrate. Here, the temperature-dependent measuring resistor is preferably manufactured by thin layer technology and the substrate is constructed as an electrically insulating ceramic, preferably consisting of Al
2
O
3
; the measuring resistor has a resistor layer made of platinum or of a platinum-based alloy. In a preferred embodiment the measuring resistor is directly mounted on the substrate, whereby the substrate and measuring resistor together form a thin layer component, on whose surface the reference resistor and the micro-module can be mounted or attached in addition.
The reference resistor preferably comprises an alloy made of nickel-chromium or constantan.
It is, however, also possible to mount both the measuring resistor and the reference resistor on the sub
Muller Andreas
Wienand Karlheinz
Akin Gump Strauss Hauer & Feld L.L.P.
Coleman William David
Heraeus Electro-Nite International N.V.
Pham Long
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