Description:TECHNICAL FIELD
The present invention relates to a Transducer device. The invention specifically relates to Transducer; a multi-plate capacitive sensor. The capacitive transducer device (A) is configured for accurate measurement of various parameters like load, displacement, position, and pressure. In particular, the capacitive sensor device (A) is adopted for concurrent measurement of displacement and load. The invention also relates to the method of fabrication of said device (A) economically.

BACKGROUND AND PRIOR ART
The role of transducers in the accurate measurement of parameters like load, displacement, position, pressure, weight, acceleration is ubiquitously acknowledged. The capacitive transducers sense the change in capacitance between two or more electrodes caused by a change in position of at least one electrode to provide the results.
Prior arts inform about various capacitive transducers, however most of them are disadvantageous for accurate measurements; due to the design of sensor plate stack up, has more compliance, non - linearity and low sensitivity. Further, the factors like temperature, noise, mechanical imperfections and tolerance stackup add to the disadvantages.
Patent no US. 5,576,483 titled, “Capacitive transducer with electrostatic actuation”, informs about a capacitive transducer, the disclosed transducer therein is complex in its features and requires management of parasitic capacitance and typical insulations. Another disclosure, Patent no.US 8,189,300 titled “Multi-layer capacitive transducer with multi dimensional operation” adopts adhesives to stack up and assemble the sensor parts, the adhesives in between each layer of the device has its own compliance due to its elastic behaviour which gets added to the overall compliance including the mounting structure and the measurements recorded are non linear.
Further, said prior art transducers have individual sensor packs assembled into a support that has more compliance. Also the load actuating mechanism rests on the displacement sensor thereby decreasing the range of the sensor due to deadweight. Along with this, the unidirectional adjustable mechanism provided to overcome the compliance range, induces nonlinear measurements thereby further decreasing the range of the displacement sensor.
It is necessary to address the limitations of prior arts like dead weight and its related sag, reduced sensitivity after assembly, decrease in the range, increase in the compliance, errors due to assembly to beget a robust accurate transducer. Further, it would be advantageous if multi parameters are analysed concurrently to mitigate the time of analysis and effort.

SUMMARY OF INVENTION
The present invention provides -
a configurable uniaxial multi parameter sensing capacitive transducer(A) comprising a rigid frame (1), a sensor (2), a sensor (5), flexural member (18, 28), actuator (7) and floating electrodes (22 ,32); wherein
the sensor (2) with the spacer (21) placed in between load sensor flexure member (28) and floating electrode (22) is assembled with the Actuator (7);
a floating electrode (32) is placed between the sensor electrodes (24, 26) with spacer (31) between the floating electrode (32) and displacement sensor flexure member (18) and attached to actuator(7) to beget the sensor (5);the sensor (5) and the actuator (7) is connected on the displacement sensor’s (2) translating flexure member (18);
a probe(46) attached at the bottom sensor bolt (3) to transfer reaction force sensor (5) and sensor(2), through the center translating axis consisting a bottom displacement bolt (3), a displacement flexure (18), a spacer (21), in between the flexure (18) and the floating sensing electrode (22) tightened with the center stud (4), and a load sensor floating sensing electrode (32), a spacer (31) in between the electrode (32) and the flexure member (28) is tightened with a top load sensor bolt (10) to the center stud (4);
the sensor (5) is placed on top of sensor (2) along with probe(46) with central translating axis and assembled within the rigid frame (1) through bolts (9,12);
the bolt (9) and nut (13) supporting the actuator (7) are adjusted to correct position errors.

A configurable uniaxial displacement and/or load parameter sensing capacitive transducer (A) comprising a rigid frame (1), a displacement sensor (2), a load sensor (5), flexural member (18, 28), actuator (7) and floating electrodes (22 ,32); wherein
the displacement sensor (2) with the spacer (21) placed in between load sensor flexure member (28) and floating electrode (22) is assembled with the Actuator (7);
a floating electrode (32) is placed between the sensor electrodes (24; 26);
a spacer (31) in between the floating electrode (32) and the load sensor flexure member (28) is placed and attached to the actuator (7) to beget the load sensor (5);the load sensor (5) and the actuator (7) is connected on the displacement sensor’s (2) translating flexure member (18);
a probe (46) attached at the bottom sensor bolt (3) to transfer reaction force load sensor (5) and displacement sensor (2), through center translating axis consisting of bottom displacement bolt (3), a displacement flexure (18), a spacer (21), in between the flexure (18) and the floating sensing electrode (22) tightened with the center stud (4), and a load sensor floating sensing electrode (32), a spacer (31) in between the electrode (32) and the flexure member (28) is tightened with a top load sensor bolt (10) to the center stud (4);
the displacement sensor (2), load sensor (5), and probe (46) with central translating axis are assembled within the rigid frame (1) through bolts (9, 12); and
the bolt (9) and nut (13) supporting the actuator (7) are adjusted to correct position errors.
A method of sensing displacement and/or load through capacitive transducer (A),said method comprising acts of ,
a. placing the specimen in contact with probe (46) and applying known load or displacement through the actuator;
b. recording the change in capacitance of floating electrode (22) as voltage difference through the instrumentation circuit (52) to sense the displacement of specimen;
c. recording the change in capacitance of the floating electrode (32) as voltage difference through instrumentation circuit (52) to sense the load acting on the specimen; and
d. translating the voltage difference into measurable data to sense the displacement and/or load parameter.

BRIEF DESCRIPTION OF FIGURES
The appended figures form part of specification. The features of the present invention can be understood in detail with the aid of figures, in combination with the detailed description of the specific embodiments presented herein. It is to be noted, however, that the appended figures illustrate only typical embodiments of this invention and therefore not to be considered limiting of its scope for the invention.
Figure 1: Shows schematic of the transducer device (A)
Figure 2: Shows schematic of the front view of the transducer device (A).
Figure 3: shows schematic sectional view of the side view of the transducer device (A).
Figure 4: shows schematic view of the Displacement Sensor (2).
Figure 5: shows schematic view of the Load Sensor (5).
Figure 6: shows schematic view of the Extended Leads of the electrodes and the Fastening Holes for individual sensors.
Figure 7: shows schematic view of Flexure member (18) and (28).
Figure 8: shows schematic view of the Piezo actuator (7) assembled with the supporting plates (6, 8).
Figure 9: shows schematic view of the Piezo actuator (7) bottom supporting plate (6).
Figure 10: shows schematic view of the Piezo actuator (7) top supporting plate (8).
Figure 11: shows schematic view of the load sensor (5) with the floating electrode (32) and the insulating spacer (31).
Figure 12: shows schematic view of the load sensor (5) assembly with the piezo actuator assembly depicted in the figure 8.
Figure 13: shows schematic view of the load sensor (5) and piezo actuator (7) assembly depicted in the figure 12 with the displacement sensor (2) and its floating electrode assembly.
Figure 14: shows the schematic view of the complete transducer assembly with the adjustment mechanism.
Figure 15: shows the block diagram of the transducer device (A) with instrumentation board.
Figure 16: shows the schematic representation of the test data from the sensor.

Figure 17: shows the graph of displacement v. load for a typical example

DETAILED DESCRIPTION OF INVENTION
The foregoing description of the embodiments of the invention is presented for the purpose of illustration. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, as many modifications and variations are possible in light of this disclosure for a person skilled in the art in view of the figures, description and claims. It may further be noted that as used herein and in the appended claims, the singular “a” “an” and “the” include plural reference unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by a person skilled in the art.
In some embodiments, the numerical parameters should be constructed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations.
Abbreviations and tradenames:
List of some important abbreviations and tradenames used herein are as follows-
SNR- Signal to Noise Ratio
CTE - Coefficient of Thermal Expansion
DAQ - Data Acquisition
ADC - Analog to Digital Converter
DAC - Digital to Analog Converter
Macor - A machinable glass ceramic- an insulator and a rigid material.
BeCu - Beryllium Copper
The present invention provides a configurable uniaxial multi parameter sensing capacitive transducer device (A). The device (A) can be adopted in a facile manner for measuring load, displacement, pressure, weight, position, temperature either in one dimension or two dimensions depending on the user preference. It can also be used for measuring velocity and acceleration as a derived parameter. In the current instance, it is used for measuring the load and displacement in the Z-axis.
The transducer device (A) of the present invention is adopted for the instrumented indentation technique, where the load and displacement data are recorded with a high resolution of 1 ppm.
The transducer device (A), offers the advantage of the reduction of the compliance thereby minimising the error factor by limiting the usage of the adhesive and movement of the piezo actuator (7) in one direction. The floating electrodes (22, 32) are of non contact type, where the sensitivity is decoupled from translating flexure members (18, 28) to ensure better linearity and less compliance. It also comprises the adjustable mechanism of the floating electrodes (22, 32) by which the counter effects from the dead weight and the sag within can be adjusted irrespective of the direction. The fasteners at every level of the assembly ensures the decrease in the compliance.
The actuator (7) is rigidly supported on the rigid frame (1) by fastening the piezo actuator top supporting plate (8) to frame with an adjustment bolt (9) and 2 nuts (13). The actuator’s top supporting plate (43) has a tapped hole where the adjustment bolt (9) is fastened. This reduces assembly errors, sagging, deadweight effects and the compliance. The floating electrode, which is also a non contact sensing electrode, provides better signal to noise ratio (SNR), increased linearity and sensitivity than the strain gauge sensors. The inherent high performance decoupling capacitor energizes the electrodes which ensures better SNR. The transducer device (A), is based on the characteristics of reduced compliance and increased linearity with better signal to noise ratio (SNR).
In an embodiment, the device (A) comprises a rigid frame(1), displacement sensor (2), load sensor (5), flexural member (18, 28), actuator (7) and floating electrodes (22, 32). The displacement sensor (2) is coupled with a floating capacitive sensing electrode (22) using a spacer in between the flexure member and the sensing electrode (22) and assembled within the rigid frame (1); the load sensor (5) and the actuator (7) is connected on the displacement sensor’s (2) translating flexure member (18). The transducer device (A) and its sectional views are shown in figures 1-3 and figures 13 and 14.

In an embodiment of the present invention, each of the sensors (2, 5) can be used independently or concurrently in combination, depending on the user requirement. Each sensor assembly consists of a three plate capacitor configuration with a floating, non contact sensing electrode (22, 32) which ensures lower compliance and better linearity by using an inherent high performance decoupling capacitor (47, 48, 49, 50) to energise the electrodes. The Decoupling capacitors are the top and bottom electrodes. They act as capacitors due to the capacitance formed within the top plate and the ground plate placed on either side of the printed circuit boards (PCBs).
In another embodiment, the sensors (2, 5) are stacked and assembled together using bolts (9, 12) within a rigid frame (1). The capacitive area in each of the sensors (2, 5), increases the sensitivity range since the capacitance is directly proportional to the area. In an embodiment of the invention, the internal sag due to deadweight and assembly errors can be corrected or adjusted by a bolt (9) and nut (13) that supports the actuator (7).
In another embodiment of the invention, the sensors (2, 5) are assembled in a jig, by stacking the supporting plates (19, 29), flexure members (18, 28), side spacers (15, 17; 25, 27), fixed electrodes (14, 16; 24, 26), insulating spacers (21, 31) in between the flexure members (18, 28) and the floating electrode (22, 32). Once assembled, the sensors are completely tightened using fastening bolts (30). This keeps them from moving and easier to assemble within the transducer.
In another embodiment, each sensor (2, 5) comprising of a flexure member (18, 28) are supported by metallic Spacers (15, 17; 25, 27) of required thickness on either sides, a top electrode (14, 26), a bottom electrode (16, 24) and two top support plates (23, 33) that are assembled together by bolts (20, 30). The proper tightening of fastening bolts (20, 30) ensures lower compliance, since there are no compliant components between layers. The displacement sensor (2) fixed to the rigid support frame (1) by fastening bolts (12) increases the overall stiffness of the transducer(A).
In another embodiment, the sensitive regions within the sensors (2, 5) have protective mesh for ingress protection around them to protect the sensors (2, 5) from dust and moisture. The mesh is also a gaussian cage that protects the measurements from external noise, parasitic capacitance and other external electrical factors. The capacitive region consists of 3 electrodes within the individual sensors (2, 5), namely, the top electrode (14, 26), bottom electrode (16, 24) and the floating electrode (22, 32). The top (14, 26) and bottom (16, 24) electrode consists of two electrical leads (36) i.e. the ground (35) and the other is the sensing component from the top (14, 26) and the bottom electrodes (16, 24).
In another embodiment, the sensitivity of the individual sensors (2, 5) are decoupled from the flexure member (18, 28) for better SNR characteristics. The decoupling is the isolation of the signals from the floating electrodes (22, 32) by means of having an insulated member supporting the electrode i.e., nothing but the insulating spacers (21, 31).
In an embodiment, Based on the Load and Displacement characteristics as per the requirement, the flexure members (18, 28) can be modified and replaced accordingly within the individual sensors (2, 5) without replacing any other components and without any loss in the resolution and accuracy, this makes it highly customisable.
In an embodiment, the actuator (7) is used for applying the required load or displacement. Typically, the actuator can be selected from the electromechanical devices such as Piezo actuator, voice coil actuator, electrostatic actuator and the like. The actuator is chosen and customised based on the load and displacement characteristics required by the user.
In an embodiment, the transducer consists of floating electrode assembly (22, 32), one in the load sensor (5) and the other in the displacement sensor (2). The floating electrodes (22, 32) are connected through a stud (4) made of rigid and insulating material. The stud (4) isolates the capacitive signals within the sensors (2, 5). The insulating spacer (21, 31) is placed between the flexure members (18, 28) and the floating electrode (22, 32), to decouple the floating electrode (22, 32) sensitivity from the translating flexure members (18, 28). The stud (4) with threads, is easily assembled with the sensors (2, 5), it isolates the signals from each of the sensors (2, 5). The stud and the spacers are made of Macor material. It ensures rigidity and insulation between the sensors (2, 5), between the floating electrode (22, 32) and translating flexure members (18, 28). Instead of Macor material any other compatible materials can also be used.
In another embodiment, the two translating flexure members (18, 28) are made of material with good yield strength, creep resistance and lower coefficient of thermal expansion, for one each for the sensors (2, 5). Each of the flexure members (18, 28) is designed according to the requirements and the dead weight induced due to the stud (4), spacers (21, 31) and other external attachments such as probes, indenters, flat punch etc.
In still another embodiment, the flexural member (18, 28) material is UNS C17200Beryllium Copper (BeCu) alloy sheets to provide high yield strength of about 965 - 1205 MPa and CTE of 16.7 μm/m/°C at temperature 20 ℃ to 100 ℃. Lower CTE is potentially beneficial for the sensors (2, 5) as it decreases the change in the sensitivity with respect to the change in temperature. However, if a material with higher CTE is used, the material tends to react to small changes in temperature, affecting the sensitivity dynamically. The flexure members (18, 28) are designed for minimum stress of a factor of safety of 3. The life cycle of the sensors (2, 5) is considerably longer and has reduced effect on the overall sensitivity, which is translated to the transducer for holistic performance.
In still another embodiment, the load and displacement parameters of the flexure members (18, 28) are based on the user preference. For example, the transducer when used in measuring the Vickers Hardness number, the formula is “HV=0.1891*F/d^2” where ‘F’ is the force and the ‘d’ is the diagonal of the indent. The contact indentation depth ‘hc’ is given by “hc=d/7” and the maximum indentation depth hmax is 2.5 times the contact indentation depth. Considering a lower hardness number of 10 Hv for a maximum load of 30 N, the maximum indentation depth is 268 microns. Accordingly, to achieve a range of hardness of 3 Hv to 3000 Hv, maximum deflection (maximum indentation depth) of 250 microns in the displacement sensor (2) and maximum applied load of 30 N are selected. The figure 4 shows the schematic of the displacement sensor (2).
In another embodiment, the flexure member (18) of the displacement sensor (2) is made of 150 microns thick sheet and can accommodate a maximum deflection of up to 250 microns for applied load of 1 N. The stiffness of the flexure member (18) is of the range of 4 N/mm. Depending on the application of the sensors (2, 5), the range can be changed accordingly. The displacement sensor’s flexure member is mainly used for constricting the translating components to move in the other remaining axes. If said movement can be restricted then the transducer may either require the flexure member or be completely removed. Rounded relief cutouts (fillet) are provided in the design to minimize the stress concentration and increase stiffness.
In yet another embodiment, the load sensor (5) is depicted in figure 5 and 11. It is constructed the same way as the displacement sensor (2), but the flexure member (28) profile is changed and the thickness is increased to increase the stiffness. Here, the load flexure member (28) is made of 0.6 mm thick BeCu plate, in which the stiffness is calibrated including the deadweight i.e., the translating mass and the reaction load due to the displacement sensor’s stiffness acting on it. In the load sensor assembly, the fastening bolts (34) are used to rigidly constrict the sensors and fulfill the assembly. The leads (36, 37) of the electrodes, from where the capacitance is measured is depicted in the fig. 6. These leads are connected to the single strand wires from which the readings are recorded.
In another embodiment, the piezo actuator (7) as shown in figure 8 is assembled inside the frame (1) with top (8) and bottom (6) supporting plates. Both the top (8) and the bottom (6) supporting plates consist of clearance holes (41, 42) where the bolt heads of the fasteners (40) for mounting the piezo actuator sit. The Piezo actuator is fastened using the bolts (11) in the supporting plates (8, 6). The supporting plates (8, 6) are made of SS plates with provisions to accommodate the piezo actuator (7). The top supporting plate (8) enables the piezo actuator (7) to apply the load only in the direction of the indenter. The top supporting plate (8) (figure 10) is connected to the rigid frame (1) by a bolt (9) and adjustment nuts (13). The bolt (9) and adjustment nuts (13) are used to adjust the floating electrode (22, 32) position within the sensors. The bottom supporting plate (6) consists of mounting holes (39) to mount the load sensor (5). The piezo actuator (7) is assembled to the load sensor (5) as in figure 9 and figure 12.
In yet another embodiment, the individual sensor flexure members (18, 28) as depicted in figure 7 are designed for maximum load, displacement and deadweight. The unique shape and design with relief grooves (38) ensures stability in all axes, joints ensuring no slip or compliance. Based on the requirements, the flexure members (18, 28) are designed, simulated and later manufactured by chemical etching. The chemical etching process ensures the parallelism of the member and no heat affected zones in the cut outs which might change the material properties thereby affecting its performance.
In another embodiment, the floating electrode (22, 32) is positioned between two electrodes (14, 16; 24, 26) in the sensor assemblies (2, 5). The floating electrode (22, 32) is coupled directly to the flexure members (18, 28) without any side supports. Due to the direct transmission of load to the floating electrode (22, 32), there is increased sensitivity and less compliance in the measurements. With the use of an inherent high performance decoupling capacitor for energizing the electrodes, better linearity is ensured by the transducer. Since the sensitivity is decoupled from the translating flexure members (18, 28), there is reduction in the noise and its effects on the sensor electrodes (14, 16; 24, 26).
In still another embodiment, a probe (46) like for example, indenters, flat punch, ball indenters and the like, attached at the bottom displacement sensor bolt (3). The probe (46) when in contact with the external specimen to be analysed, the reaction force is transferred to the load sensor (5) and displacement sensor (2), through the center translating axis.
In an embodiment, the center translating axis assembly consists of a bottom displacement sensor’s bolt (3), a displacement flexure (18), an insulating spacer (21), in between the flexure (18) and the floating sensing electrode (22) tightened with the center stud (4), and a load sensor floating sensing electrode (32), a spacer (31) in between the electrode (32) and the flexure member (28) is tightened with a top load sensor bolt (10) to the center stud (4).
In another embodiment of the invention, the transducer is assembled in multiple steps:
a) Assembly of load sensor (5)
Floating electrode (32) is placed between the sensor electrodes (24, 26) with spacer (31) between the Floating electrode (32) and the flexure member (28) to beget the load sensor (5). The load sensor (5) is attached to the actuator (7). The load sensor fastening bolts (44) are used to mount the load sensor (5) on the piezo’s bottom supporting plate (6).
b) Assembly of displacement sensor:
The displacement sensor (2) with the spacer (21) is placed in between the flexure member (28) and the floating electrode (22). It is then assembled with the Actuator (7) and the load sensor (5).
c) Assembly of the sensors (5) and (2)

The displacement sensor (2) is placed into the rigid frame (1) and fastened to the bottom of the rigid frame (1) with the fastening bolts (45). The load sensor (5) is placed on top of the displacement sensor (2) and the sensors are tightened with a bolt (9) from the top and 2 nuts (13) within the rigid frame (1) arresting the movement of the actuator (7).
In an embodiment, when the probe (46) is in contact with specimen and the actuator is applying a known load or displacement, the reaction from the probe (46) is transformed to the displacement sensor’s flexure member (18). The flexure member (18) supports the displacement sensor’s floating electrode (22). The floating electrode (22) translates between the fixed electrodes (14, 16) of the displacement sensor (2). When the floating electrode (22) is translating, it creates a change in the capacitance between the plates that transforms as voltage difference. The voltage difference is recorded and translated into a measured displacement data multiplied by a factor i.e. the actual stiffness of the displacement sensor flexure member (18). Similarly the reaction force from the probe (46) is translated onto the floating electrode (32) of the load sensor (5). Due to the sensor’s (5) mounting position by virtue of which, the entire load sensor (5) moves with the actuator (7). The stiffness of the flexure member (28) allows the reaction force from the probe (46) to be transformed via the center stud (4) to the floating electrode (32) in between the fixed plates (24, 26) of the load sensor (5). This will change the capacitance, that is converted as the voltage difference which is then recorded as the measured load data after multiplying it by a factor based on the actual stiffness of the flexure member (28) (calibrated value). Thus, the displacement sensor’s (2) fixed position and the moving position of the load sensor (5) allows it to measure the displacement and the load simultaneously.
In another embodiment, the measured load and displacement data via a change in the capacitance is transformed into the voltage difference by an instrumentation circuit (52) with the help of the instrumentation board (51). The data is collected by the Data Acquisition (DAQ) system which is stored and used when required. Figure 15 shows the block diagram of the transducer with instrumentation circuit (52) and the instrumentation board (51).
Example 1: General Method of Instrumented Indentation Test.

In the Instrumented Indentation Test, the transducer device (A) is used for measuring the hardness number based on the indentation depth. The transducer indents the workpiece using the actuator and simultaneously measures the load and displacement characteristics. These characteristics are plotted and hardness value, elastic modulus, and various other parameters are measured. Depending on the hardness range to be measured, the sensor’s flexure members are re-calibrated and assembled based on the requirement. The figure 16 shows the schematic representation of the test data from the sensor, wherein ‘a’ is the load applied by the piezo and ‘b’ is the load removal. At both the instances, the load and displacement data is recorded and plotted as shown in the above figure 16. ‘c’ is the line drawn tangent to the ‘b’, this line is used for the analysis in determining the hardness number.
Typically as per the ISO 14577 Standards, the steps involved in measuring the hardness value involves:
a. Determining the maximum applied force (Pmax).
b. Determining the depth at maximum applied force (hmax).
c. Determining the slope (S) in the unloading curve for the 98 % to 85 % of load.
d. Determining the contact depth (hc), hc = hmax - (0.75 x Pmax / S).
e. Determining the Contact Area (Ap), Ap = 24.5 x hc^2.
f. Determining the indentation hardness (Hit), Hit = Pmax / Ap.
g. Finally, the Vickers hardness value Hv, Hv = 0.0945 x Hit.
A standard sample with HV 213 at 0.2 Kgs was tested and the values are plotted as in figure 17 and the hardness value is calculated. Accordingly, the resultant values are as given below:
a. Pmax (mN) = 2006.34.
b. hmax (nm) = 6.34896.
c. hc (nm) = 6.01873.
d. Ap (µm^2) = 887.516.
e. Hit(GPa) = 2.26062.
f. Hv = 213.629.

Example 2: General method of study of Thermal Expansion.
The transducer is also used for studying the thermal expansion of the material by replacing the probe (46) of required geometry. When the probe (46) comes in contact with the surface of the heated material, the direct change in the thermal expansion induces the probe (46) to translate the motion onto the sensors. The motion is recorded and the data is plotted with respect to time, temperature and displacement.

Advantages and unique features of the device
a. A non-Complex Displacement and Load sensor’s design which is easily configurable.
b. A floating non contact sensing electrode ensures lower compliance and better linearity.
c. An inherent high performance decoupling capability for energisation electrodes for better SNR (Signal to Noise Ratio).
d. A sensing mechanism with sensitivity decoupled from the translation flexure member for better SNR.
e. The device has a mechanism to adjust the assembly errors during the assembly process. The mechanism involves the top bolt (9) and nut (13) supporting the piezo actuator. By adjusting the nut position, the position errors caused during the assembly can be corrected. The same mechanism is used for the tare off mechanism to counter sag and dead load effects.
f. A gaussian/faraday cage for the sensing electrode.
g. All the fasteners in the sensors and the transducer assembly are tightened using torque drivers such that it ensures lower compliance.
h. Ingress protection.
i. Unique design of the flexure member based on the double cantilever design.
j. Since, the Floating Electrode is supported by the center stud, even a small tolerance in the surface will induce tilt in the floating electrode. To compensate for this, the minimum dielectric gap between the electrodes is increased such that the tilt won’t hinder the output signal. This ensures that there is no effect on the linearity of sensor output.
, C , Claims:WE CLAIM
1. A configurable uniaxial multi parameter sensing capacitive transducer (A) comprising a rigid frame (1), a sensor (2), a sensor (5), flexural member (18, 28), actuator (7) and floating electrodes (22 ,32); wherein
the sensor (2) with the spacer (21) placed in between load sensor flexure member (28) and floating electrode (22) is assembled with the Actuator (7);
a floating electrode (32) is placed between the sensor electrodes (24, 26) with spacer (31) between the floating electrode (32) and displacement sensor flexure member (18) and attached to actuator (7) to beget the sensor (5);the sensor (5) and the actuator (7) is connected on the displacement sensor’s (2) translating flexure member (18);
a probe (46) attached at the bottom sensor bolt (3) to transfer reaction force sensor (5) and sensor (2), through the center translating axis consisting a bottom displacement bolt (3), a displacement flexure (18), a spacer (21), in between the flexure (18) and the floating sensing electrode (22) tightened with the center stud (4), and a load sensor floating sensing electrode (32), a spacer (31) in between the electrode (32) and the flexure member (28) is tightened with a top load sensor bolt (10) to the center stud (4);
the sensor (5) is placed on top of sensor (2) along with probe (46) with central translating axis and assembled within the rigid frame (1) through bolts (9,12);
the bolt (9) and nut (13) supporting the actuator (7) are adjusted to correct position errors.
2. The configurable uniaxial multi parameter sensing capacitive transducer (A) as claimed in claim 1, wherein the sensing parameter is load, displacement, temperature, weight and the like.
3. The configurable uniaxial multi parameter sensing capacitive transducer (A) as claimed in claim 1 and 2, wherein the sensing parameter is either load or displacement or both concurrently by the change in capacitance through the instrumentation circuit (52 ) .
4. The configurable uniaxial multi parameter sensing capacitive transducer (A) as claimed in claim 3, wherein the capacitance is transformed into voltage difference by the instrumentation circuit (52 ).
5. The configurable uniaxial multi parameter sensing capacitive transducer (A) as claimed in claim 1, wherein the spacer (21), studs (4) are of machinable glass ceramic.
6. The configurable uniaxial multi parameter sensing capacitive transducer (A) as claimed in claim 1, wherein the probe (46) is selected from a group comprising indenters, flat punch, ball indenters and the like.
7. The configurable uniaxial multi parameter sensing capacitive transducer (A) as claimed in claim 1, wherein the actuator (7) is selected from a group comprising piezo actuator, voice coil actuator, electrostatic actuator and the like.
8. The configurable uniaxial multi parameter sensing capacitive transducer (A) as claimed in claim 1, wherein the flexural member (18, 28) is of material is of Beryllium Copper (BeCu) alloy.
9. A configurable uniaxial displacement and/or load parameter sensing capacitive transducer (A) comprising a rigid frame (1), a displacement sensor (2), a load sensor (5), flexural member (18, 28), actuator (7) and floating electrodes (22 ,32); wherein
the displacement sensor (2) with the spacer (21) placed in between load sensor flexure member (28) and floating electrode (22) is assembled with the Actuator (7);
a floating electrode (32) is placed between the sensor electrodes (24; 26);
a spacer (31) in between the floating electrode (32) and the load sensor flexure member (28) is placed and attached to the actuator (7) to beget the load sensor (5); the load sensor (5) and the actuator (7) is connected on the displacement sensor’s (2) translating flexure member (18);
a probe (46) attached at the bottom sensor bolt (3) to transfer reaction force load sensor (5) and displacement sensor (2), through center translating axis consisting of bottom displacement bolt (3), a displacement flexure (18), a spacer (21), in between the flexure (18) and the floating sensing electrode (22) tightened with the center stud (4), and a load sensor floating sensing electrode (32), a spacer (31) in between the electrode (32) and the flexure member (28) is tightened with a top load sensor bolt (10) to the center stud (4);
the displacement sensor (2), load sensor (5), and probe (46) with central translating axis are assembled within the rigid frame (1) through bolts (9, 12); and
the bolt (9) and nut (13) supporting the actuator (7) are adjusted to correct position errors.

10. A method of sensing displacement and/or load through capacitive transducer (A), said method comprising acts of ,
a. placing the specimen in contact with probe (46) and applying known load or displacement through the actuator;
b. recording the change in capacitance of floating electrode (22) as voltage difference through the instrumentation circuit (52) to sense the displacement of specimen;
c. recording the change in capacitance of the floating electrode (32) as voltage difference through instrumentation circuit (52) to sense the load acting on the specimen; and
d. translating the voltage difference into measurable data to sense the displacement and/or load parameter.