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FORM 2
THE PATENT ACT 1970 (as amended)
[39 OF 1970]
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
[See Section 10 and Rule 13]
TITLE: “AN APPARATUS TO DETECT AN OPEN CIRCUIT CONDITION OF
A THERMOCOUPLE AND A METHOD THEREOF”
Name and address of the Applicant:
TATA MOTORS LIMITED, an Indian company having its registered office at
Bombay house, 24 Homi Mody Street, Hutatma Chowk, Mumbai 400 001, Maharashtra,
INDIA.
Nationality: INDIAN
The following specification particularly describes the nature of the invention and the
manner in which it is to be performed.
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TECHINCAL FIELD
Embodiments of the present disclosure relate to a thermocouple circuit. More
particularly, the embodiments relate to detecting an open circuit condition of the
thermocouple.
BACKGROUND OF DISCLOSURE
A thermocouple is a bi-metallic junction device for electrically measuring
temperature. The bi-metallic junction of the thermocouple produces a voltage across the
junction in accordance with the temperature of the thermocouple. However, if the two
metals associated with the bi-metallic junction lose the contact with one another, then an
open circuit failure condition results and the thermocouple will no longer produce the
desired voltage.
In measurement applications, a thermocouple may be inserted into a system for
monitoring the temperature of a given element for regulating the temperature of the
system. The thermocouple produces a voltage when the temperature of system varies.
The voltage produces by the variation in the temperature is read by an instrument for
detecting when the temperature of the element exceeds a predetermined threshold. Thus,
corrective actions will be taken to avoid the variation in the temperature. However, if the
thermocouple fails, it cannot detect the variation in the temperature. Thus, the system
may also fail. It is therefore desirable to periodically check the thermocouple for an open
circuit condition in order to verify whether the device is functional.
Currently, the detection of each thermocouple open circuit failure mounted on
each wheel of vehicle to measure the brake temperature is performed by comparison
method. If the temperature difference of a thermocouple in comparison with other three
thermocouples is greater than a predetermined value then that thermocouple whose
temperature is not increased reasonably be declared as an open thermocouple. The
drawback of this method is that to wait for time duration till the temperature of all the
thermocouples reach above the ambient, as at ambient thermocouple produces zero volts.
Thus, the comparison of one thermocouple with the other thermocouples is not possible
at initial stage of the system operation. Another drawback of this method is that, it is not
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possible to detect the failure condition of all the four thermocouples, if all the
thermocouples fail at the same time.
Hence, there is a need of a solution which can detect the thermocouple open
circuit failure at initial stage of system operation in order to avoid wrong interpretation of
temperature value by system and thus avoiding system failure.
OBJECTIVES OF THE DISCLOSURE
The objective of the present disclosure is to provide an apparatus to detect an
open circuit condition of a thermocouple.
Another objective of the present disclosure is to provide a method of detecting an
open circuit condition of a thermocouple.
SUMMARY
The shortcomings of the prior art are overcome and additional advantages are
provided through the provision as claimed in the present disclosure.
Additional features and advantages are realized through the techniques of the
present disclosure. Other embodiments and aspects of the disclosure are described in
detail herein and are considered a part of the claimed disclosure.
In one embodiment, the disclosure provides an apparatus to detect an open circuit
condition of a thermocouple. The apparatus comprises differential amplifier to generate a
differential voltage output across the thermocouple. The inputs terminals of the
differential amplifier are connected to the terminal of the thermocouple. Also, the
apparatus comprises a filter circuit connected to output of the differential amplifier to
filter noise in the differential voltage output. Further, the apparatus comprises a transistor
switch to activate a connection of a predetermined voltage supply to one of the terminals
of the thermocouple. A control unit is configured in the apparatus to control the transistor
switch. The control unit receives the filtered output from the filter circuit as an input,
compares the input with a predefined value to detect the open circuit condition of the
thermocouple.
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In one embodiment, the disclosure provides a method of detecting an open circuit
condition in a thermocouple. The method comprises applying a predefined amount of
voltage to one of the terminals of the thermocouple connected to a differential amplifier
for generating a differential output voltage. The predefined amount of voltage is applied
to one terminal of the thermocouple by switching a transistor switch using a control unit.
The method also comprises comparing the generated differential output voltage with a
predefined value performed by a control unit to detect the open circuit condition in the
thermocouple.
The foregoing summary is illustrative only and is not intended to be in any way
limiting. In addition to the illustrative aspects, embodiments, and features described
above, further aspects, embodiments, and features will become apparent by reference to
the drawings and the following detailed description.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
The novel features and characteristic of the disclosure are set forth in the appended
claims. The disclosure itself, however, as well as a preferred mode of use, further
objectives and advantages thereof, will best be understood by reference to the following
detailed description of an illustrative embodiment when read in conjunction with the
accompanying figures. One or more embodiments are now described, by way of example
only, with reference to the accompanying figures wherein like reference numerals
represent like elements and in which:
Figure 1 shows a circuit diagram illustrating detection of an open circuit condition for
thermocouple, as one embodiment.
The figures depict embodiments of the disclosure for purposes of illustration only. One
skilled in the art will readily recognize from the following description that alternative
embodiments of the structures and methods illustrated herein may be employed without
departing from the principles of the disclosure described herein.
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DETAILED DESCRIPTION
The foregoing has broadly outlined the features and technical advantages of the
present disclosure in order that the detailed description of the disclosure that follows may
be better understood. Additional features and advantages of the disclosure will be
described hereinafter which form the subject of the claims of the disclosure. It should be
appreciated by those skilled in the art that the conception and specific embodiment
disclosed may be readily utilized as a basis for modifying or designing other structures
for carrying out the same purposes of the present disclosure. It should also be realized by
those skilled in the art that such equivalent constructions do not depart from the spirit and
scope of the disclosure as set forth in the appended claims. The novel features which are
believed to be characteristic of the disclosure, both as to its organization and method of
operation, together with further objects and advantages will be better understood from the
following description when considered in connection with the accompanying figures. It is
to be expressly understood, however, that each of the figures is provided for the purpose
of illustration and description only and is not intended as a definition of the limits of the
present disclosure.
Referring now to the drawings wherein the drawings are for the purpose of
illustrating an exemplary embodiment of the disclosure only, and not for the purpose of
limiting the same.
To overcome the drawbacks mentioned in the background, the disclosure provides
an apparatus and a method for detecting thermocouple open circuit failure.
Exemplary embodiments of the present disclosure provide an apparatus and a
method for detecting open circuit failure for thermocouples.
In one embodiment, to detect open circuit failure for thermocouples, a transistor
switch is used at thermocouple voltage reading circuit i.e. input circuit. A thermocouple
voltage at both ambient as well as at thermocouple open circuit failure is zero. Hence, it
is very difficult to distinguish between the normal condition and thermocouple open
circuit failure condition at ambient. Under normal condition as well as the open circuit
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condition the thermocouple is checked by turning ON the transistor switch. The transistor
switch is switched ON/OFF using an application. In this embodiment, the transistor under
OFF condition will not affect the normal functionality of input circuit.
At normal conditions if the transistor is ON in one embodiment, the apparatus for
detecting the open circuit for the thermocouple gives an output of logic LOW i.e. 0 volts,
which is read by a control unit to generate a signal for normal operating condition of the
system. The control unit is a microcontroller.
In one embodiment, when the open circuit failure condition occurs for
thermocouple, the apparatus of detecting the open circuit for thermocouple produces
logic HIGH i.e. 4.7 Volts output, which is read by microcontroller to generate a signal for
failure condition of the system.
Figure 1 shows the apparatus 100 for detecting the open circuit condition of
thermocouple 101. Each arm of the thermocouple 101 is connected to the arms of the
differential amplifier. The apparatus comprises a transistor switch 106 which can be
turned ON/OFF automatically using a control unit or a microcontroller 105. The
controlling of the transistor switch using the control unit is user defined. The
microcontroller receives the output of the circuit/ apparatus 100 to detect the open circuit
condition of the thermocouple. Thus, the microcontroller 105 automatically detects
thermocouple normal condition or open circuit condition based on the received data from
the output of the differential amplifier apparatus that is by comparing the output with a
predefined value. Thus, the apparatus detects the open circuit condition of thermocouple
101.
The apparatus or circuit for detecting open circuit condition of a thermocouple
comprises the blocks Electromagnetic interference (EMI)/ Electromagnetic Compatibility
(EMC) Electrostatic discharge (ESD) protection block 102, a differential amplifier 103, a
low pass filter 104, transistor switch 106 and a control unit 105, in one embodiment. A
differential amplifier block 103 is protected against the electromagnetic interference
using the EMI/ EMC ESD block 102. The terminals of the thermocouple 101 are
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connected to the input terminals of the differential amplifier 103 via EMI/ EMC ESD
block 102. The differential amplifier block 103 output is connected to a low pass filter
104 for filtering out the noise. The filtered output is provided to the microcontroller 105.
The microcontroller 105 detects the open circuit condition of the thermocouple 101 based
on the received differential output.
In one embodiment, under normal operating condition if the transistor Q1 of the
transistor switch 106 is OFF, the differential amplifier 103 multiplies the thermocouple
101 output by applying a gain of about 300 and provides the output to the microcontroller
105.
Under normal operating condition, when the transistor Q1 of the transistor switch
106 is ON, the predetermined power supply 5 volts will appears at the positive terminal
of the op-amp U1 of the differential amplifier 103. Since the thermocouple 101 has very
low resistance path, the 5 volts also appears at negative terminal of op-amp. Since the
same voltage i.e. 5 volts is applied to both the input terminals of the differential amplifier
103 the output is zero differential voltage. A filter circuit or low pass filter 104 is used to
filter out noise in the differential voltage output of the differential amplifier103. The
filtered output voltage value i.e. 0 volt is provided to the control unit or the microcontroller
105. The microcontroller 105 turns ON the transistor Q1 whenever it intends to
check the thermocouple 101 open condition.
In one embodiment, when the thermocouple 101 is in open condition and
transistor Q1 is ON, 5 volts appears at the positive terminal of the op-amp U1 i.e. of the
differential amplifier 103. Because of the broken thermocouple or open circuited
thermocouple, the differential amplifier 103 acts as a buffer and generates an output of 5
volts. The output voltage value 5 volt is provided to the micro-controller 105. Thus by
reading 5 volts at its pins, microcontroller determines that the thermocouple 101 is open.
If the transistor switch 106 is ON and the input to micro-controller is 0 volt, then
it can be concluded that the thermocouple is working in normal condition. Whereas, if the
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transistor switch 106 is ON and the input to micro-controller 105 is 5 volt, then it can be
concluded that the thermocouple is under open circuited condition.
In one embodiment, the transistor switch 106 is used to connect plurality of
thermocouples through the connections 107 to the predetermined voltage supply of 5
volts to detect the open circuit in the thermocouples. As one skilled in art can understand
that, the circuit as shown in figure 1 has to be replicated to each thermocouple having a
common transistor switch 106. Each diode output D3, D4 and D5 can then be connected
to respective arm of the thermocouple.
One embodiment of the disclosure is a method of detecting an open circuit
condition in a thermocouple. The method comprises applying a predefined amount of
voltage to one of the terminals of the thermocouple connected to a differential amplifier
for generating a differential output voltage. The predefined amount of voltage is applied
to one terminal of the thermocouple by switching a transistor switch using a control unit.
The method also comprises comparing the generated differential output voltage with a
predefined value performed by a control unit to detect the open circuit condition in the
thermocouple.
The application of apparatus and method provided in the present disclosure is to
detect the open circuit of thermocouples, where each of the thermocouple is used to
measure brake temperature of each wheel in a vehicle.
The present disclosure is not to be limited in terms of the particular embodiments
described in this application, which are intended as illustrations of various aspects. Many
modifications and variations can be made without departing from its spirit and scope, as
will be apparent to those skilled in the art. Functionally equivalent methods and devices
within the scope of the disclosure, in addition to those enumerated herein, will be
apparent to those skilled in the art from the foregoing descriptions. Such modifications
and variations are intended to fall within the scope of the appended claims. The present
disclosure is to be limited only by the terms of the appended claims, along with the full
scope of equivalents to which such claims are entitled. It is also to be understood that the
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terminology used herein is for the purpose of describing particular embodiments only,
and is not intended to be limiting.
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.
In addition, where features or aspects of the disclosure are described in terms of
Markush groups, those skilled in the art will recognize that the disclosure is also thereby
described in terms of any individual member or subgroup of members of the Markush
group.
While various aspects and embodiments have been disclosed herein, other aspects
and embodiments will be apparent to those skilled in the art. The various aspects and
embodiments disclosed herein are for purposes of illustration and are not intended to be
limiting, with the true scope and spirit being indicated by the following claims.
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We claim
1. An apparatus to detect an open circuit condition of a thermocouple comprising:
Differential amplifier to generate a differential voltage output across the
thermocouple, wherein each terminal of the thermocouple is connected to input
terminals of the differential amplifier;
a filter circuit connected to output of the differential amplifier to filter noise in the
differential voltage output;
a transistor switch to activate a connection of predetermined voltage supply to one
of the terminals of the thermocouple; and
Control unit configured to control the transistor switch, said control unit receives
the filtered output from the filter circuit as an input, compares the input with a
predefined value to detect the open circuit condition of the thermocouple.
2. The apparatus as claimed in claim 1, wherein the control unit is a microcontroller.
3. The apparatus as claimed in claim 1, wherein the transistor switch connects the
predetermined voltage supply to plurality of thermocouples for detecting the open
circuit condition.
4. The apparatus as claimed in claim 1, wherein the filter circuit is a low pass filter.
5. A method of detecting an open circuit condition in a thermocouple comprising:
applying a predetermined amount of voltage to a terminal of the thermocouple
connected to a differential amplifier for generating a differential output voltage,
wherein said predefined amount of voltage is applied by switching a transistor switch;
and
comparing the generated differential output voltage with a predefined value to
detect the open circuit condition in the thermocouple.
6. The method as claimed in claim 5, wherein the generated differential voltage is nonzero
when the thermocouple is open circuited.
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7. The method as claimed in claim 5, wherein the open circuit condition is detected for
plurality of thermocouples by connecting a predetermined voltage supply to each
thermocouple through the transistor switch.
8. The method as claimed in claim 5, wherein the differential output voltage is filtered
using a low pass filter to remove noise.