Title of Invention	A FLUID FLOW METER
Abstract	Title: A fluid flow meter A fluid flow meter which comprises a pair of 0.3 mole La-dopped barium titanate positive temp coefficient thermistor sensor, characterized in that the said sensors being provided with pair of electrodes on either side, the said electrode pairs being connected to AC 4-5V & DC 2-6V sources respectively, the said sensors being placed so that one of the sensors is in the dynamic gas flow path (called as dynamic sensor) and the other sensor is in static gas environment to provide reference (called as static reference sensor), the outputs of the said dynamic sensor and of the said static reference sensor being connected to a tuned amplifier through an AC bridge, the output of the said tuned amplifier being connected to digital display through a detector and analogue digital converter.

Title of Invention

A FLUID FLOW METER

Abstract

Title: A fluid flow meter A fluid flow meter which comprises a pair of 0.3 mole La-dopped barium titanate positive temp coefficient thermistor sensor, characterized in that the said sensors being provided with pair of electrodes on either side, the said electrode pairs being connected to AC 4-5V & DC 2-6V sources respectively, the said sensors being placed so that one of the sensors is in the dynamic gas flow path (called as dynamic sensor) and the other sensor is in static gas environment to provide reference (called as static reference sensor), the outputs of the said dynamic sensor and of the said static reference sensor being connected to a tuned amplifier through an AC bridge, the output of the said tuned amplifier being connected to digital display through a detector and analogue digital converter.

Full Text	The present invention relates to a fluid flow meter. The present invention particularly relates to a fluid flow meter using a Positive Temperature Coefficient (PTC) Thermistor as the sensor. It is useful in the detection of fluid flow at various ranges. Air flow measurement is very common in various types of applications. Historically air velocity measurement was very necessary for the measurement of atmospheric air f flow. Now a days flow of fluid are very widely used in various scientific and industrial application and the measurement of quantity of fluid flow plays a very important role in this processes. A few common example are various kinds of chemical processes where specific rate of gas or air flow is necessary for continuous chemical reactions to occur. Flow of fluid is produced in various kind of pumps compressor or fans. It is obvious that some kind of instrument or gauge is necessary to measure the amount of flow. The instrument used for this purpose is normally known as "Flow meter". A large number of different type of such gauges are working on different principle have been designed for over year by various workers and many of them are being produced commercially. This may be broadly classified in two types a) Electric flowmeters: Which are also of two types i)Thermal conducivity gauge like Hot wire anemometer etc. and ii) Mechanial gauges like Turbine anemometer and secondly by b) the Non-electric flowmeter like i) Venturimeter and ii) Pitot tubes. Most of the above devices available for measuring the fluid flow in the range 1 to 150 ml/minute and sensitivity as well as accuracy decreases in the range below 100 ml/min.Other limitation lies in resolution which is not less than 1 ml/min. The Electrical flow meter are obviously more reliable and accurate and are most commonly used in process control applications. Among all the various type of electrical gauges mentioned above, the present investigation related to only the Thermal conductivity gauges both in terms of working principle and the range of measurement. Therefore a more detailed description of this type of gauge are presented here for better understanding of the importance of the present invention. a n^inooim«*c^ The most important component of the hot wire anomometer,which is based on the theory of thermal conductivity, is the heated wire (generally made up of Platinum and a temperature sensor kept downstream at the flow direction. The amount of conducted heat is calibrated with the flow rate. There may be different sources of error in the process of detection. The following disadvantages apply in the system: Higher price: The supplied current to the filament should be very constant. Accuracy of the sensing system must be very high since the temperature change is very small, a constant current supply and an accurate sensor make the sytem much costly. Delicate: The thin wire used in the system are brittle and has to be handled with care in harsh environments. Size: The sensor and heat source are separated by a conducting path. So the sensor size is bigger which results in precision measurment in small areas. The main objective of the present invention is to provide a Fluid flow meter using Positive temperature coefficient thermistor as sensor which obviates the disadvantages mentioned above. Another objective of present invention is to provide a device having a very good sensitivity in the range 0 to 150 cc/min with a resolution of 0.1 cc/min with a response time of 0.9 sees. PTC thermistor is made frm barium titanate based ceramic material Compared to pure barium titanate its electrical resistance at room temperature is much lower due to doping with small amounts of certain oxides like those of Lanthanum, Antimony, Niobium, etc. Such a doped barium titante ceramic, semi conducting in nature show a very steep rise in resistively around it ferroelectric Curie temperature of 120°C. The sensor of the device of the present invention is a PTC thermistor material of doped barium titanate material which is useful for low flow rate measurement providing benefit of measuring flow rate from very low to high level so as to get appropriate sensitivity. The uniqueness of the present invention lies in the fact that it has find good sensitivity in the range (0 to 15 cc/min. with 0.5 cc/min resolution and with a quick response time ( Accordingly the present invention provides a fluid flow meter which comprises a pair of 0.3 mole La-dopped barium titanate positive temp coefficient thermistor sensor, characterized in that the said sensors being provided with pair of electrodes on either side, the said electrode pairs being connected to AC 4-5V & DC 2-6V sources respectively, the said sensors being placed so that one of the sensors is in the dynamic gas flow path (called as dynamic sensor) and the other sensor is in static gas environment to provide reference (called as static reference sensor), the outputs of the said dynamic sensor and of the said static reference sensor being connected to a tuned amplifier through an AC bridge, the output of the said tuned amplifier being connected to digital display through a detector and analogue digital converter. In the device of the present invention useful for the detection of low rate of gases, the sensor used consists of La-doped barium titanate tape cast thermistor sensor having room temperature resistance in the range of 10ohm, Curie temperature of 120°C and jump in the range of three orders. The senor being provided with four electrodes for connecting to the measuring circuit the electrode of the said sensor are excited by DC source and rest two electrodes are connectign to the measuring circuit the electrode of the said sensor are excited by DC source and rest two electtrodes are excited by an AC signal of frequauency (1khz) the said frequency is detected by converter for digital display. Figs. 1&2 of the drawings accompanying this specification shows an embodiment of the present invention. In an embodiment the device in the present invention has a sensor with four electrodes with high temperature coefficient of resistance. The sensor is made of Lanthanum doped barium titanate tape cast thermistor material having a Curie temperature of 120°C with a room temperature resistance approximately 10 ohm and jump height of three orders. The sensor is mounted on a polyethylene has which is fitted to cylindrical metallic tube. The tube has one outlet and one inlet provided with a said tube for fixing a reference sensor on dental characteristics with similar four proble arrangement. The sensor works on the basic principle that when a small voltage of a certain angular frequency (1kHz) is introduced to it while it is excited by a DC, the AC voltage. will vary according to the change of flow rate which control the dissipation of the sensor. The difference in voltage are calibrated for different flow rates in the measurement of fluid flow. The working of the fluid flow meter of the present invention is detailed below: The current-voltage characteristsic of a PTC thermistor is sensitive to change in the flow rate of the surrounding fluid. When the flow rate is very low the rate of energy transfer between the self-heated thermistor and its ambient is proportional to the flow rate and their temperature difference. The thermistor are self-heated close to their Curie temperature by application of an appropriate DC voltage from the voltage source. When the gas flow rate in both the chamber of the gauge are identical and the tempereature of the thermistors are allowed to reach a steady state condition the output voltage measured by the voltmeter of the bridge become negligible.Under operating conditions one of the thermistors is exposed to flowing fluid the other remaining in static fluid. This causes a difference in the heat transfer coefficient of the two element and therefore tend to maintain two difference temperature of the element leading to an unbalnce condition of the bridge and an increased output voltage. Due to the presence of the two identical thermistors in two different arms of the bridge the output signal remains insensitive to and change in ambient temperature. The following examples illustrate the invention in the manner in which it may be carried out in practice however this should not be construed to limit the scope of the present invention. Example 1 A PTC material is used with barium titanate doped with lanthanum oxide (0.3mole%) having Curie temperature 120°C room temperature resistance of l0ohm and PTCR jump of three orders. The sensor is excited by a DC voltage (1 volts). Power dissipation is 2.3watt across the sample. Resolution at different flow rates is found to be 0.1 volt/cc/min and the response time of rise is found to be 0.9 secs, and fall is 1.2 secs. S/N ratio was found to be 13.44 Exampel 2 A PTC material is used with barium titanate doped with lanthanum oxide (0.3 mole% having Curie temperature 120°C room temperature resistance of 10 ohm and PTCR jump of two orders. The sensor is excited by a DC voltate (1 volts) Power dissipation is 2.7 watts across the sample. The resolution at different flow rates is found to be 0.1 volt/cc/min and the response time of rise is found to be 0.9 sees, and fall is 1.1 sees.S/N ratio found to be 15.27. Example 3 A PTC material is used with barium titanate doped with lanthanum oxide (0.3 mole%) having Curie temperature 120°C room temperature resistance of 10 ohm and PTCR jump of four orders. The sensor is excited by a DC voltage (1 volts) Power dissipation is 2.1 watt across the sample. Resolution at different flow rates is found to be 0.1 volt/cc/min and the response time of rise is found to be 0.6 sees and fall is 0.8 sees. S/N ratio is found to be 12.18. The main advantages of the flow meter of the present invention are: 1 .High sensitivity (2 mv/. 1ml/min) 2.First response (> 1 sec. 3.Temperature stability over full range (upto 0-150 ml/min.) 4.Not sensitive to electrical noise 5.Practically no drift over time up (1.50 ml/min) We Claim: 1. A fluid flow meter which comprises a pair of 0.3 mole La-dopped barium titanate positive temp coefficient thermistor sensor, characterized in that the said sensors being provided with pair of electrodes on either side, the said electrode pairs being connected to AC 4-5V & DC 2-6V sources respectively, the said sensors being placed so that one of the sensors is in the dynamic gas flow path (called as dynamic sensor) and the other sensor is in static gas environment to provide reference (called as static reference sensor), the outputs of the said dynamic sensor and of the said static reference sensor being connected to a tuned amplifier through an AC bridge, the output of the said tuned amplifier being connected to digital display through a detector and analogue digital converter. 2. A fluid flow meter substantially as herein described with reference to the examples and drawing accompanying this specification.

Full Text

The present invention relates to a fluid flow meter. The present invention particularly relates to a fluid flow meter using a Positive Temperature Coefficient (PTC) Thermistor as the sensor. It is useful in the detection of fluid flow at various ranges.
Air flow measurement is very common in various types of applications. Historically air velocity measurement was very necessary for the measurement of atmospheric air
f flow. Now a days flow of fluid are very widely used in various scientific and industrial
application and the measurement of quantity of fluid flow plays a very important role in
this processes. A few common example are various kinds of chemical processes where specific rate of gas or air flow is necessary for continuous chemical reactions to occur.
Flow of fluid is produced in various kind of pumps compressor or fans. It is obvious that some kind of instrument or gauge is necessary to measure the amount of flow. The instrument used for this purpose is normally known as "Flow meter". A large number of different type of such gauges are working on different principle have been designed for over year by various workers and many of them are being produced commercially. This may be broadly classified in two types a) Electric flowmeters: Which are also of two types i)Thermal conducivity gauge like Hot wire anemometer etc. and ii) Mechanial gauges like Turbine anemometer and secondly by b) the Non-electric flowmeter like i) Venturimeter and ii) Pitot tubes.
Most of the above devices available for measuring the fluid flow in the range 1 to 150 ml/minute and sensitivity as well as accuracy decreases in the range below 100 ml/min.Other limitation lies in resolution which is not less than 1 ml/min.
The Electrical flow meter are obviously more reliable and accurate and are most commonly used in process control applications. Among all the various type of electrical gauges mentioned above, the present investigation related to only the Thermal conductivity gauges both in terms of working principle and the range of measurement. Therefore a more detailed description of this type of gauge are presented here for better
understanding of the importance of the present invention.
a n^inooim«*c^ The most important component of the hot wire anomometer,which is based on the
theory of thermal conductivity, is the heated wire (generally made up of Platinum and a
temperature sensor kept downstream at the flow direction. The amount of conducted heat
is calibrated with the flow rate. There may be different sources of error in the process of
detection. The following disadvantages apply in the system:
Higher price: The supplied current to the filament should be very constant. Accuracy of
the sensing system must be very high since the temperature change is very small, a
constant current supply and an accurate sensor make the sytem much costly.
Delicate: The thin wire used in the system are brittle and has to be handled with care in
harsh environments.
Size: The sensor and heat source are separated by a conducting path. So the sensor size is
bigger which results in precision measurment in small areas.
The main objective of the present invention is to provide a Fluid flow meter using Positive temperature coefficient thermistor as sensor which obviates the disadvantages mentioned above.
Another objective of present invention is to provide a device having a very good sensitivity in the range 0 to 150 cc/min with a resolution of 0.1 cc/min with a response time of 0.9 sees.
PTC thermistor is made frm barium titanate based ceramic material Compared to pure barium titanate its electrical resistance at room temperature is much lower due to doping with small amounts of certain oxides like those of Lanthanum, Antimony, Niobium, etc. Such a doped barium titante ceramic, semi conducting in nature show a very steep rise in resistively around it ferroelectric Curie temperature of 120°C.
The sensor of the device of the present invention is a PTC thermistor material of doped barium titanate material which is useful for low flow rate measurement providing benefit of measuring flow rate from very low to high level so as to get appropriate sensitivity. The uniqueness of the present invention lies in the fact that it has find good sensitivity in the range (0 to 15 cc/min. with 0.5 cc/min resolution and with a quick response time ( Accordingly the present invention provides a fluid flow meter which comprises a pair of 0.3 mole La-dopped barium titanate positive temp coefficient thermistor sensor, characterized in that the said sensors being provided with pair of electrodes on either side, the said electrode pairs being connected to AC 4-5V & DC 2-6V sources respectively, the said sensors being placed so that one of the sensors is in the dynamic gas flow path (called as dynamic sensor) and the other sensor is in static gas environment to provide reference (called as static reference sensor), the outputs of the said dynamic sensor and of the said static reference sensor being connected to a tuned amplifier through an AC bridge, the output of the said tuned amplifier being connected to digital display through a detector and analogue digital converter.
In the device of the present invention useful for the detection of low rate of gases, the sensor used consists of La-doped barium titanate tape cast thermistor sensor having room temperature resistance in the range of 10ohm, Curie temperature of 120°C and jump in the range of three orders. The senor being provided with four electrodes for connecting to the measuring circuit the electrode of the said sensor are excited by DC source and rest two electrodes are connectign to the measuring circuit the electrode of the said sensor are excited by DC source and rest two electtrodes are excited by an AC signal of frequauency (1khz) the said frequency is detected by
converter for digital display.
Figs. 1&2 of the drawings accompanying this specification shows an embodiment of the present invention. In an embodiment the device in the present invention has a sensor with four electrodes with high temperature coefficient of resistance. The sensor is made of Lanthanum doped barium titanate tape cast thermistor material having a Curie temperature of 120°C with a room temperature resistance approximately 10 ohm and jump height of three orders. The sensor is mounted on a polyethylene has which is fitted to cylindrical metallic tube. The tube has one outlet and one inlet provided with a said tube for fixing a reference sensor on dental characteristics with similar four proble arrangement.
The sensor works on the basic principle that when a small voltage of a certain angular frequency (1kHz) is introduced to it while it is excited by a DC, the AC voltage.
will vary according to the change of flow rate which control the dissipation of the sensor. The difference in voltage are calibrated for different flow rates in the measurement of fluid flow.
The working of the fluid flow meter of the present invention is detailed below: The current-voltage characteristsic of a PTC thermistor is sensitive to change in the flow rate of the surrounding fluid. When the flow rate is very low the rate of energy transfer between the self-heated thermistor and its ambient is proportional to the flow rate and their temperature difference. The thermistor are self-heated close to their Curie temperature by application of an appropriate DC voltage from the voltage source. When the gas flow rate in both the chamber of the gauge are identical and the tempereature of the thermistors are allowed to reach a steady state condition the output voltage measured by the voltmeter of the bridge become negligible.Under operating conditions one of the thermistors is exposed to flowing fluid the other remaining in static fluid. This causes a difference in the heat transfer coefficient of the two element and therefore tend to maintain two difference temperature of the element leading to an unbalnce condition of the bridge and an increased output voltage. Due to the presence of the two identical thermistors in two different arms of the bridge the output signal remains insensitive to and change in ambient temperature.
The following examples illustrate the invention in the manner in which it may be carried out in practice however this should not be construed to limit the scope of the present invention.
Example 1
A PTC material is used with barium titanate doped with lanthanum oxide (0.3mole%) having Curie temperature 120°C room temperature resistance of l0ohm and PTCR jump of three orders. The sensor is excited by a DC voltage (1 volts). Power dissipation is 2.3watt across the sample. Resolution at different flow rates is found to be 0.1 volt/cc/min and the response time of rise is found to be 0.9 secs, and fall is 1.2 secs. S/N ratio was found to be 13.44
Exampel 2
A PTC material is used with barium titanate doped with lanthanum oxide (0.3 mole% having Curie temperature 120°C room temperature resistance of 10 ohm and PTCR jump of two orders. The sensor is excited by a DC voltate (1 volts) Power dissipation is 2.7 watts across the sample. The resolution at different flow rates is found to be 0.1 volt/cc/min and the response time of rise is found to be 0.9 sees, and fall is 1.1 sees.S/N ratio found to be 15.27.
Example 3
A PTC material is used with barium titanate doped with lanthanum oxide (0.3 mole%) having Curie temperature 120°C room temperature resistance of 10 ohm and PTCR jump of four orders. The sensor is excited by a DC voltage (1 volts) Power dissipation is 2.1 watt across the sample. Resolution at different flow rates is found to be 0.1 volt/cc/min and the response time of rise is found to be 0.6 sees and fall is 0.8 sees. S/N ratio is found to be 12.18.
The main advantages of the flow meter of the present invention are:
1 .High sensitivity (2 mv/. 1ml/min)
2.First response (> 1 sec.
3.Temperature stability over full range (upto 0-150 ml/min.)
4.Not sensitive to electrical noise
5.Practically no drift over time up (1.50 ml/min)

We Claim:
1. A fluid flow meter which comprises a pair of 0.3 mole La-dopped barium titanate positive
temp coefficient thermistor sensor, characterized in that the said sensors being provided with
pair of electrodes on either side, the said electrode pairs being connected to AC 4-5V & DC
2-6V sources respectively, the said sensors being placed so that one of the sensors is in the
dynamic gas flow path (called as dynamic sensor) and the other sensor is in static gas
environment to provide reference (called as static reference sensor), the outputs of the said
dynamic sensor and of the said static reference sensor being connected to a tuned amplifier
through an AC bridge, the output of the said tuned amplifier being connected to digital
display through a detector and analogue digital converter.
2. A fluid flow meter substantially as herein described with reference to the examples and
drawing accompanying this specification.

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Patent Number

215772

Indian Patent Application Number

329/DEL/1999

PG Journal Number

12/2008

Publication Date

21-Mar-2008

Grant Date

03-Mar-2008

Date of Filing

25-Feb-1999

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	KAMALENDU SENGUPTA	CENRAL GLASS& CERAMIC RESEARCH INSTITUTE, CALCUTTA 700032, INDIA.
2	SUMAN CHATTERJEE	CENRAL GLASS& CERAMIC RESEARCH INSTITUTE, CALCUTTA 700032, INDIA.
3	HIMADRI SHEKHAR MAITI	CENRAL GLASS& CERAMIC RESEARCH INSTITUTE, CALCUTTA 700032, INDIA.

PCT International Classification Number

G01F 1/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA