Claims:1. An apparatus for sensing the temperature of a resistive temperature device (RTD) sensor and a positive temperature coefficient (PTC) sensor, the apparatus comprising:
a plurality of resistors;
a plurality of amplifiers;
a plurality of transistors;
wherein the plurality of resistors coupled to the at least one amplifier and the at least one transistor;
wherein the resistive temperature device (RTD) sensor and/or the positive temperature coefficient (PTC) sensor is adapted for receiving a current flow such that the resistive temperature device (RTD) sensor and/or the positive temperature coefficient (PTC) sensor gets excited;
wherein voltage across the resistive temperature device (RTD) sensor and/or the positive temperature coefficient (PTC) sensor is amplified using the amplifier such that the voltage is processed by an analog to digital converter;
wherein the resistive temperature device (RTD) sensor and/or the positive temperature coefficient (PTC) sensor is adapted to generate two different resistance values at same temperature such that an amplifier gain is switched using the transistor.

2. The apparatus as claimed in claim 1, wherein the plurality of transistors defined as a first transistor, a second transistor.

3. The apparatus as claimed in claim 1 or 2, wherein the apparatus is adapted for selecting the positive temperature coefficient (PTC) sensor if the first transistor is opted for OFF condition.

4. The apparatus as claimed in claim 3, wherein if the apparatus is adapted for selecting the positive temperature coefficient (PTC) sensor, then an output of constant current source is 0.5mA.

5. The apparatus as claimed in claim 1 or 2, wherein the apparatus is adapted for selecting the resistive temperature device (RTD) sensor if the first transistor is opted for ON condition.

6. The apparatus as claimed in claim 5, wherein if the apparatus is adapted for selecting the resistive temperature device (RTD) sensor, then an output of constant current source is 1mA.

7. The apparatus as claimed in claim 1 or 2, wherein the apparatus is adapted for selecting the positive temperature coefficient (PTC) sensor if the second transistor is opted for OFF condition.

8. The apparatus as claimed in claim 1 or 2, wherein, the apparatus is adapted for selecting the resistive temperature device (RTD) sensor if the second transistor is opted for ON condition.
, Description:TECHNICAL FIELD

[001] The present subject matter described herein, in general, relates to resistive temperature device (RTD) sensor, positive temperature coefficient (PTC) sensor, and more particularly a common signal conditioning circuit for processing the data of two different types of sensors, i.e. RTD and PTC sensors in a protection relay.

BACKGROUND

[002] Conventional methods of temperature sensing include the design of two separate variants of protection relays, one for processing the data of resistance temperature detector(RTD) sensor and other for processing the data of binary positive temperature coefficient (PTC) sensor. This method results in increase of the variants of a product which in turn increases the overall cost of product.

[003] US 20020075938 A1 entitled “Setting-free resistive temperature device (RTD) measuring module” discloses generally to resistive temperature devices (RTDs) and more specifically concerns a RTD measuring module which is part of a specific system arrangement involving a RTD, an RTD measuring module and a remote device such as a protective relay, which uses the RTD information from the RTD measuring module. It is all about measuring the resistance of a plurality of RTDs present at a selected site and is then transmitted in a known order to a remote protective relay which determines the correct temperature and take the further decision.

[004] DE 2935807 A1 entitled “Overload protection circuit - has PTC resistor in series with load and shunted by overload warning lamp” discloses the overload protection circuit which has a temperature-sensitive resistor (a PTC resistor) connected in series with the component (e.g. a motor) being protected. The resistor's resistance increases rapidly as the current through it increases. A warning lamp is connected across the resistor and receives progressively more current as the resistor's resistance increases. Two such PTC resistors may be connected in series, the warning lamp shunts one of them, whilst an acoustic alarm shunts both of them. Three such PTC resistors may be connected in series; the warning lamp shunts one, the acoustic alarm shunts two, and a cutout relay shunts all three. The circuit may be rearranged so that an NTC resistor can be used instead of a PTC resistor.

[005] In the existing technology, the inventions are about sensing the temperature of the remote area by incorporating a single type of temperature sensor, either RTD or PTC in remote area. The module designed for sensing the RTD sensor cannot be utilized for sensing the PTC sensor and vice versa.

[006] Thus, there is a need to develop an apparatus for sensing the temperature of RTD and PTC sensor, which provides the provision of sensing the temperature of both RTD and PTC sensor. Hence, a single temperature measuring module can be used in protective relay to take an appropriate action for clearing fault condition.

SUMMARY
[007] This summary is provided to introduce concepts related to, an apparatus for sensing the temperature of RTD and PTC sensor, and the same are further described below in the detailed description. This summary is not intended to identify essential features of the claimed subject matter nor is it intended for use in determining or limiting the scope of the claimed subject matter.

[008] According to one aspect of the invention, there is provided an apparatus for sensing the temperature of a resistive temperature device (RTD) sensor and a positive temperature coefficient (PTC) sensor, the apparatus comprising: a plurality of resistors; a plurality of amplifiers; a plurality of transistors; wherein the plurality of resistors coupled to the at least one amplifier and at least one transistor; wherein the resistive temperature device (RTD) sensor and/or the positive temperature coefficient (PTC) sensor is adapted for receiving a current flow such that the resistive temperature device (RTD) sensor and/or the positive temperature coefficient (PTC) sensor gets excited; wherein voltage across the resistive temperature device (RTD) sensor and/or the positive temperature coefficient (PTC) sensor is amplified using the amplifier such that the voltage is processed by an analog to digital converter; wherein the resistive temperature device (RTD) sensor and/or the positive temperature coefficient (PTC) sensor is adapted to generate two different resistance values at same temperature such that an amplifier gain is switched using the transistor.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[009] The detailed description is described with reference to the accompanying figures. In the figures, the digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to refer like features and components.

[0010] Figure1 illustrates a schematic circuit diagram of constant current source of the present invention.

[0011] Figure2 illustrates a signal conditioning circuit diagram of the present invention.

[0012] It is to be understood that the attached drawings are for purposes of illustrating the concepts of the invention and may not be to scale.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0013] The following clearly describes the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are merely a part rather than all of the embodiments of the present invention. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0014] A detailed description of one or more embodiments of the invention is provided below along with accompanying figures that illustrate the principles of the invention. The invention is described in connection with such embodiments, but the invention is not limited to any embodiment. The scope of the invention is limited only by the claims and the invention encompasses numerous alternatives, modifications and equivalents. Numerous specific details are set forth in the following description in order to provide a thorough understanding of the invention. These details are provided for the purpose of example and the invention may be practiced according to the claims without some or all of these specific details. For the purpose of clarity, technical material that is known in the technical fields related to the invention has not been described in detail so that the invention is not unnecessarily obscured.

[0015] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components, modules, units and/or circuits have not been described in detail so as not to obscure the invention.

[0016] Although embodiments of the invention are not limited in this regard, the terms “plurality” and “a plurality” as used herein may include, for example, “multiple” or “two or more”. The terms “plurality” or “a plurality” may be used throughout the specification to describe two or more components, devices, elements, units, parameters, or the like. Unless explicitly stated, the method embodiments described herein are not constrained to a particular order or sequence. Additionally, some of the described method embodiments or elements thereof can occur or be performed simultaneously, at the same point in time, or concurrently.

[0017] The present invention relates to an apparatus for sensing the temperature of RTD and PTC sensor i.e. a common signal conditioning circuit for processing the data of two different types of sensors, i.e. RTD and PTC temperature sensors. The circuit includes a constant current source that can provide two different values of constant current by switching the resistor values of an operation amplifier using a transistor. A constant current of 1mA will be generated by current source if RTD type sensor is selected and a constant current of 0.5mA is sourced when PTC (Binary) type sensor is selected. The sourced current flows into the sensor for its excitation. The voltage across the sensor is then amplified using an operation amplifier so that it can be processed by the analog to digital converter. The resistance value of both the sensors are different at same temperature so amplifier gain is also switched using a transistor in signal conditioning section.

[0018] Figure 1 shows the circuit of a constant current source with the transistor Q1 added in order to select the type of temperature sensor and accordingly source the current from the constant source. When Binary PTC type sensor is selected then transistor Q1 is OFF and the output of the current source is 0.5mA whereas when RTD sensor is selected, the transistor Q1 is ON and the constant current of 1mA is sourced.

[0019] Figure 2 shows the signal conditioning circuit for processing the data of temperature sensors. When Binary PTC type sensor is selected, the transistor Q2 is OFF and the gain required for processing the data of PTC sensor is generated through Operation amplifier U41, and the conditioned signal is send to analog to digital converter U37 for sampling and further processing. Similarly, when the RTD sensor is selected, the transistor Q2 is ON and the gain value is changed for the further processing.

[0020] ADVANTAGES:
• A variant of the protection relays is reduced since a single unit can now process the data of RTD and PTC sensor.
• Product cost is reduced since the number of variants of a product is reduced.
• Site selectable sensor type feature in protection relays.

[0021] The invention has been described in a preferred form only and many variations may be made in the invention which will still be comprised within its spirit. The invention is not limited to the details cited above. An apparatus for sensing the temperature of RTD and PTC sensor as described above does not limit the scope of the present invention. The structure thus conceived is susceptible of numerous modifications and variations, all the details may furthermore be replaced with elements having technical equivalence. In practice the materials and dimensions may be any according to the requirements, which will still be comprised within its true spirit.

[0022] Finally, the language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by any claims that issue on an application based here on. Accordingly, the disclosure of the embodiments of the invention is intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims.

[0023] With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.