Title of Invention

"A NOVEL MOISTURE SENSOR"

Abstract A novel moisture sensor, which comprises 32-37 gauge, enameled copper coil wound on a porous tape cast tubular ceramic former enclosing a low density ceramic ferrite having diameter in the range of 10- 12mm, length in the range 100-120-cm.
Full Text The invention relates to a novel moisture sensor and a device for measuring
moisture made thereof. This invention particularly relates to a sensor based
on change in quality factor of a coil due to be absorption of moisture from
high to low level.
Measurement of moisture in general and gases in particular is very common
in various types of applications especially for industrial processes where
moisture sensitivity dictates product quality and yield. The various
techniques for measuring moisture from extreme low to high value are
mainly done in two methods. Which are the measurement of ac impedance
and measurement of change in capacitance. In case of capacitative sensor a
hygroscopic layer of aluminium oxide absorbs water molecules within its
pores, depending on the water vapour pressure in its environment. The
electrical capacitance is measured between the aluminium core of the sensor
and the porous conductive gold layer on the outside. For conductive type
sensor the hygroscopic material is either deposited on impervious insulating
surfaces, on fibers or fabrics or on porous ceramics. These methods of
detection suffer from various limitations such as, it will take a long time to
come to equilibrium with the surrounding atmosphere, thus the dynamic
response is poor and the indication of the system will show a lag, sometimes
several hours. These methods of detection also suffer from various other
limitations such as low sensitivity and high cost. To the best of our
knowledge and belief there is no inductance type moisture sensor.
The main object of the present invention is to provide a novel moisture
sensor that obviates the above noted drawbacks.
Another object of the present invention is to provide a novel moisture sensor
that works on the principle of change in inductance.
Yet another object of the present invention is to provide a moisture sensor
having a tape cast porous ceramic of composition
Still another object of the present invention is to provide a device
incorporating the sensor of the present invention for measuring moisture
having fine sensitivity in the range of 100 ppm to 400 ppm with 0.05%
resolution and response time less than 3 seconds.
The moisture sensor of the present invention essentially consists of a
enameled copper coil wound on a porous tape-cast tubular ceramic former
enclosing a low density ceramic ferrie.
Accordingly the present invention provides a novel moisture sensor, which comprises 32-37 gauge,
Enameled copper coil wound on a porous tape cast tubular ceramic former enclosing a low density
ceramic ferrite having diameter in the range of 10-12mm, length in the range 100-120-cm.
In an embodiment of the present invention the copper coil may have 30-40 turns.
In another embodiment of the present invention the porous tape cast tubular former may be made
using material of pore size in the range of 0.1-0.6μm and having a composition such as
In yet another embodiment the ferrite core used may have permeability in the rnge of 2000-8000,
inductance 10-50μH, Q factor 200-250.
Accordingly, the present invention provides a device for measuring moisture, which comprises a
novel moisture sensor, as, described above, being connected to an oscillator capable of inputting an
angular frequency, the output of the said sensor being connected to a known Data Acquisition
system.
Field of application of the sensor of the present invention is for measuring moisture in any
industrial process, some applications may be measurement moisture of powdered material,
moisture present in non-toxic gases, agricultural field, food processing, for RH (relative
humidity) measurement.
The sensor works on the basic principle that a small voltage of certain
frequency (800 KHz) is introduced to the sensor, the sensor shows some
open circuit voltage, when it is placed in dry gas. When the moist gas is
passed through the sample holder, due to the extremely small size of the
pore, their Brownian motion will be limited, their energy will consequently
be reduced and they will condense into liquid water. As a result the Q value
will change. This change in Q value is measured as an index of moisture
content at the testing zone.
The novelty of the present invention resides in providing an inductance type
moisture sensor. The inventive steps are providing an enameled copper coil
wound on porous ceramic tubular tape cast former with ferrite core.
The following examples illustrate the invention and 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
An enameled copper wire of 32 gauge is wound on porous tubular ceramic
with core of permeability 2300, its dc resistivity is > ohm, relative
dissipation factor is is accommodation factor D 25°C is dry gas to 250 and its inductance is made to l0μH using 33 turns at 1MHz.
Q & L value are measured by LCR meter (HP4284A). The resonance is
adjusted to zero volts at dry gas. At l00ppm of gas moisture level the sensor
output becomes 50m V.
Example 2
An enameled copper wire of 32 gauge is wound on porous tubular ceramic
with core of permeability 2300, its dc resistivity is > ohm, relative
dissipation factor is is accommodation factor D 25°C is dry gas to 250 and its inductance is made to l0μH using 33 turns at 1MHz.
The Q and L value are measured by LCR meter (HP4284A) and the
resonance is adjusted to zero volts at dry gas. At 150ppm of gas moisture
level the sensor output becomes l00mV.
Example 3
An enameled copper wire of 32 gauge is wound on porous tubular ceramic
with core of permeability 2300, its dc resistivity is > ohm, relative
dissipation factor is is accommodation factor D 25°C is dry gas to 250 and its inductance is made to l0μH using 33 turns at 1MHz.
LCR meter (HP4284A) measures the Q and L value and the resonance is
adjusted to zero volts at dry gas. At 175ppm of gas moisture level the sensor
output becomes 200m V.
Example 4
An enameled copper wire of 32 gauge is wound on porous tubular ceramic
with core of permeability 2300, its dc resistivity is > ohm, relative
dissipation factor is is accommodation factor D 25°C is dry gas to 250 and its inductance is made to l0μH using 33 turns at 1MHz.
The Q and L value are measured by LCR meter (HP4284A) and the
resonance is adjusted to zero volts at dry gas. At 200ppm of gas moisture
level the sensor output becomes 250mV.
Example 5
An enameled copper wire of 32 gauge is wound on porous tubular ceramic
with core of permeability 2300, its dc resistivity is > ohm, relative
dissipation factor is is accommodation factor D 25°C is <. the q value is adjusted with> dry gas to 250 and its inductance is made to l0μH using 33 turns at 1MHz.
The Q and L value are measured by LCR meter (HP4284A) and the
resonance is adjusted to zero volts at dry gas. At 300ppm of gas moisture
level the sensor output becomes 350mV.
Example 6
An enameled copper wire of 32 gauge is wound on porous tubular ceramic
with core of permeability 2300, its dc resistivity is > ohm, relative
dissipation factor is ^ 1.6, temperature coefficient - 0.6 to + .6 106/K and D
is accommodation factor D 25°C is dry gas to 250 and its inductance is made to l0μH using 33 turns at 1MHz.
The Q and L value are measured by LCR meter (HP4284A) and the
resonance is adjusted to zero volts at dry gas. At 400ppm of gas moisture
level the sensor output becomes 1V.
The main advantages of the device of this present invention are:
1. High resolution
2. High range (100 - 23.000ppm)
3. High stability
4. Low cost
5. Quick response (

We Claim:
LA novel moisture sensor, which comprises 32-37 gauge, enameled copper coil wound on a
porous tape cast tubular ceramic former enclosing a low density ceramic ferrite having
diameter in the range of 10-12mm, length in the range 100-120-cm.
2. A novel moisture sensor as claimed in Claim 1 wherein the copper coil has 30-40 turns.
3. A novel moisture sensor as claimed in claim 1-2 wherein porous tape cast tubular former is
made using material of pore size 0. l-0.6μm and having composition.

Homogenizer (cyclohexanone) 0.90-1.10-wt%
4. A novel moisture sensor as claimed in Claim 1-3 wherein the said ceramic ferrite has
permeability in the range of 2000-8000, inductance 10-50μH, Q (Magnification factor of the
coil) factor 200-250.
5. A device for measuring moisture which comprises connecting the said novel moisture
sensor as claimed in claim 1 to an oscillator for inputting an angular frequency, output of
the said sensor being connected to a known data acquisition system.
6. A novel moisture sensor substantially as herein described with reference to the examples.

Documents:

361-DEL-2001-Abstract (27-03-2001).pdf

361-DEL-2001-Claims (27-03-2001).pdf

361-DEL-2001-Correspondence-Others (27-03-2001).pdf

361-DEL-2001-Correspondence-PO (27-03-2001).pdf

361-DEL-2001-Description (Complete) (27-03-2001).pdf

361-DEL-2001-Form-1 (27-03-2001).pdf

361-DEL-2001-Form-2 (27-03-2001).pdf

361-DEL-2001-Form-3 (27-03-2001).pdf


Patent Number 222433
Indian Patent Application Number 361/DEL/2001
PG Journal Number 36/2008
Publication Date 05-Sep-2008
Grant Date 08-Aug-2008
Date of Filing 27-Mar-2001
Name of Patentee COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH
Applicant Address RAFI MARG, NEW DELHI-110 001, INDIA.
Inventors:
# Inventor's Name Inventor's Address
1 SANTANU BASU CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, CLCUTTA 700 032, (INDIA).
2 SUMAN CHATTERJEE CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, CULCUTTA 700 032, INDIA.
3 DEBDAS CHATTOPADHYAY CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, CULCUTTA 700 032, INDIA.
4 KAMALENDU SENGUPTA CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, CULCUTTA 700 032, INDIA.
PCT International Classification Number G01N 27/12
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA