WO2023211373A2

WO2023211373A2 - Read-out apparatus and method for a sensor array

Info

Publication number: WO2023211373A2
Application number: PCT/SG2023/050272
Authority: WO
Inventors: Huanqian ZHANG; Jee Chin TEOH; Chwee Teck Lim; Mark Francis DE LEON; Lye Peng CHIA
Original assignee: Flexosense Pte Ltd; National University of Singapore
Current assignee: Flexosense Pte Ltd; National University of Singapore
Priority date: 2022-04-25
Filing date: 2023-04-21
Publication date: 2023-11-02
Anticipated expiration: 2024-10-25
Also published as: CN119110893A; WO2023211373A3

Abstract

In a described embodiment, a sensor array including a plurality of resistive elements arranged in a plurality of rows and columns is provided. A row driving unit is configured to connect a plurality of rows of the resistive elements of the sensor array to a voltage source for driving the voltage source to a row of the resistive elements. The row driving unit further includes switching units for performing a switching operation, row driving amplifiers, and feedback instrumentation amplifiers (FBIAs). Each of the switching units is selectively coupled to each of the row driving amplifiers and each of the row driving amplifiers is further coupled to each of the plurality of FBIAs. A column scanning unit for detecting a voltage signal of a resistive element includes column operational amplifiers. Each of the column operational amplifiers is further connected to a column of the sensor array.

Description

Read-out Apparatus and Method for a Sensor Array

Field of the Invention

The present application relates to read-out apparatus and method for a sensor array.

Background

A resistive sensor array (RSA) is used for enhancing measurement resolution in various wearable electronics and health sensing related applications including temperature and tactile sensing. In order to greatly reduce the complexity and power consumption of the sensor system, an RSA is typically implemented with a shared row (M) and shared column (N) configuration, such that each resistive element is placed between a row electrode and a column electrode in the sensor array. However, this row-column implementation often introduces crosstalk current between neighbouring or adjacent resistive elements sharing a common row or column in the array, which leads to high measurement error when scanning a resistive element of interest in the sensor array.

To reduce crosstalk current effects, some known read-out circuit configurations include using a row driver composed of digital buffers or composed of only operational amplifiers for providing voltage to drive the resistive elements of the sensor array. However, these readout implementations are ill-suited due to large measurement errors or a requirement of large power consumption or system complexity. Moreover, such known approaches solely evaluate RSAs with resistor values of high resistance (e.g. > 100 Q) due to limitations imposed by construction materials, fabrication techniques and sensing mechanisms of certain mechanical sensors and actuators.

Therefore, it is desirable to provide a read-out apparatus for a sensor array to address the disadvantages or limitations of the existing art or to at least provide the public with a useful choice.

Summary of the Invention

The present invention aims to provide new and useful apparatuses and methods which may reduce measurement errors in a sensor array, and in particular arranging resistive elements of a sensor array, driving a voltage source to a row of the resistive elements and detecting a voltage signal of a resistive element in the sensor array for minimizing errors created by crosstalk currents induced in the sensor array. In broad terms, the present invention proposes a read-out apparatus including a sensor array comprising a plurality of resistive elements arranged in a plurality of rows and columns. On way of implementing this apparatus is configuring a row driving unit to connect a voltage source to a plurality of rows of the resistive elements of the sensor array for driving the voltage source to a row of the resistive elements, wherein the row driving unit includes a plurality of switching units, a plurality of row driving amplifiers, and a plurality of feedback instrumentation amplifiers (FBIAs), wherein each of the switching units performs a switching operation and is selectively coupled to each of the row driving amplifiers and each of the row driving amplifiers is coupled to each of the FBIAs.

In one embodiment, a resistor may be connected between a non-inverting input terminal of each of the plurality of row driving amplifiers and each switching unit and each of the switching units may be selectively coupled to the row driving amplifiers via the non-inverting input terminal according to a first or second state of the switching unit

In implementations, the row driving unit may further include a plurality of current sensing resistors, wherein each current sensing resistor may be coupled to a non-inverting input terminal of each of the plurality of row driving amplifiers and one or more of the FBIAs amplify voltage across one or more of the current sensing resistors.

The read-out apparatus may reduce parasitic effects attributable to at least one of parasitic resistance from one or more connection or printed circuit board (PCB) wires of the sensor array and an offset voltage applied between the input terminals of the row driving amplifiers.

In implementations, the read-out apparatus may reduce crosstalk current effects associated with reading of a resistive element of interest in a selected row of the sensor array, wherein the crosstalk current effects are attributable to one or more neighbouring resistive elements arranged in the same column or different row as the resistive element of interest, wherein the neighbouring resistive elements are not read in association with the reading of the resistive element of interest.

In some embodiments, the apparatus may include a column scanning unit for detecting at least one voltage signal of a resistive element, wherein the column scanning unit includes a plurality of column operational amplifiers, wherein each of the column operational amplifiers is connected to a column of a plurality of columns of the sensor array. The column scanning unit may further include a plurality of feedback resistive elements, wherein each feedback resistive element is connected between an output terminal of a column operational amplifier and an inverting input terminal of said column operational amplifier, and each of the plurality of column operational amplifiers includes a non-inverting input terminal connected to ground.

The sensor array can have m number of column connections and n number of row connections and each of the plurality of the resistive elements is connected between a corresponding one of the m column connections and a corresponding one of the n row connections.

In one aspect, the column scanning unit may further include a plurality of neighbouring resistive elements not read in association with reading of a resistive element of interest, wherein each neighbouring resistive element is connected to an inverting input terminal of each column scanning unit and a feedback resistive element corresponding to each column scanning unit.

The voltage source can be configured to apply a voltage to one or more of the resistive elements of the sensor array via one or more switching units operating in a first state.

In implementations, the sensor array may be used for sensing microfluidic pressure and each of the resistive elements have a minimum resistance of 10 ohms and a maximum resistance of 200 ohms.

The sensor array can be a resistive sensor array suitable for small-scale electronic devices for replicating the function of human skin.

Zero or negligible current flow can be achieved through each row of a plurality of neighbouring resistive elements associated with a resistive element of interest when reading the resistive element of interest.

A voltage drop across each of the resistive elements of the sensor array can be adjusted in response to determined parasitic effects attributable to parasitic resistance from one or more connection or printed circuit board (PCB) wires of the sensor array or an offset voltage applied between the input terminals of the row driving amplifiers. In implementations, the plurality of feedback instrumentation amplifiers (FBIAs) may include an inverting input terminal and an non-inverting input terminal, wherein the non-inverting input terminal is connected to a first end of a first switching unit and a first end of a first current sensing resistor, the inverting input terminal is connected to a second end of the first switching unit and a second end of the first current sensing resistor, and the first switching unit and the current sensing resistor are connected in parallel.

A row of the resistive elements may include at least one resistive element having a first end coupled to one end of a current sensing resistor and one end of a switching unit and a second end coupled to one end of a neighbouring resistive element.

The resistive elements of the sensor array may include one or more resistive elements configured to detect a measurable level of voltage, current or resistance value.

Each of the plurality of row driving amplifiers may include a non-inverting input terminal connected to a switching unit and connected to ground via a single resistor, wherein the noninverting input terminal is selectively connected to the voltage source based on a state of the connected switching unit.

An output of each of the plurality of FBIAs may be connected to an inverting input terminal of each of the row driving amplifiers via a first resistor and the inverting input terminal is further connected to an output of each of the row driving amplifiers via a second resistor, wherein the first and second resistor are connected in series between the output of each FBIA and the output of each row driving amplifier.

According to a further aspect of the invention, there is provided a non-transitory computer readable medium including executable instructions for measuring a voltage value of a resistive element of a sensor array using the read-out apparatus as described above.

According to a further aspect of the invention, there is provided a method for using a readout apparatus for measuring a voltage value of a resistive element, the method may include the following steps: arranging a plurality of resistive elements of a sensor array; connecting a plurality of rows of the resistive elements of the sensor array to a voltage source via a row driving unit for driving the voltage source to a row of the resistive elements, wherein the row driving unit includes a plurality of switching units, a plurality of row driving amplifiers, and a plurality of feedback instrumentation amplifiers (FBIAs), wherein each of the switching units is selectively coupled to each of the plurality of row driving amplifiers and each of the row driving amplifiers is coupled to each of the plurality of FBIAs; and performing a switching operation via the plurality of switching units;

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 Drawings:

Embodiments of the invention will now be explained for the sake of example only, with reference to the following figures in which:

Figure 1 is a schematic diagram illustrating induced crosstalk current paths in a resistive sensor array, according to an embodiment the present disclosure.

Figure 2 is a circuit diagram illustrating a dynamic zero current method (DZCM) circuit design for a 4 x 4 sensor array, according to an embodiment the present disclosure.

Figures 3A and 3B are simplified circuit diagrams illustrating a zero-potential method (ZPM) and a DZCM circuit design for one unmeasured resistor, according to an embodiment the present disclosure.

Figure 4 is a simplified circuit diagram illustrating a DZCM circuit model for a 2x2 sensor array including parasitic effects and crosstalk current effects, according to an embodiment the present disclosure.

Figure 5 is a DZCM sensor array network extracted and analysed with Kirchhoff’s law, according to an embodiment the present disclosure.

Figures 6A and 6B are graphs illustrating an effect of a resistor of interest (R_x) on a measurement error of various Sensor array sizes (SAR) with an unmeasured resistor (R_um) set at 200 ohms and 1 ohm respectively for a DZCM and ZPM circuit design, according to an embodiment the present disclosure.

Figure 7 is a graph illustrating the effect of a resistor of interest (R_x) on various unmeasured resistors (R_um) with a Sensor array size (SAR) set to 2 x 2 for a DZCM and ZPM circuit design, according to an embodiment the present disclosure.

Figures 8A-8F are graphs illustrating the effect of a parasitic resistance (R_par) of both row and column wires, the effect of a parasitic resistor of column wires (R_parcoi), or the effect of a parasitic resistor of row wires (R_parR_Ow) on the measurement error of various Sensor array sizes (Sar) set to 6 x 6, 12 x 12 when a resistor of interest (R_x) is set to an unmeasured Resistor (R_um) of 1 ohm, 50 ohms, and 200 ohms, according to an embodiment the present disclosure.

Figures 9A-9F are graphs illustrating the effect of an offset voltage of column amplifiers (Vos_c) or offset voltage of row amplifiers (Vos_R) on measurement errors of various Sensor array sizes (S_ar) set to 6x6, 12x12, when a resistor of interest (R_x) is set to an unmeasured Resistor (R_um) of 1 ohm, 50 ohms, and 200 ohms, according to an embodiment the present disclosure.

Figure 10 is a block diagram illustrating an example computer system for implementing some or all of the schematics of Figures 1-5 for performing a readout of the sensor array.

Detailed Description of the Embodiments

Figure 1 is a schematic diagram 100 illustrating induced crosstalk current paths in a 3 x 3 resistive sensor array, according to an embodiment of the present disclosure.

Referring to the circuit schematic 100, each resistive element (E.g. R22) of the array is positioned between a row electrode and a column electrode, utilizing a row-column configuration. This resistive sensor array (RSA) configuration reduces the number of connections and simplifies sensor manufacturing. However, the row-column configuration presents an undesired crosstalk between neighbouring unmeasured elements R_um, as illustrated in Figure 1 . The resistor positioned between the driven row electrode (xth row electrode) and the scanned column electrode (yth column electrode) is designated as the resistive element being scanned, for instance, R22. When attempting to read the value of the resistive element, other parasitic paths involving adjacent unmeasured resistors appear in parallel with the resistive element, as denoted by the dashed arrows in Figure 1.

For example, in order to determine the resistance of the targeted resistor 'R22', it is necessary to evaluate the current flowing through it, denoted as ' I22' , and the voltage difference across the element, denoted as 'U22'. The voltage difference 'U22' is equivalent to the voltage difference between the row and column wires, namely 'Vrow2-Vcol2'. Conversely, ' I22' cannot be directly measured, as the current ' Icol2' in the column wire includes crosstalk currents from neighbouring unmeasured resistors R_um, as exemplified by the dashed arrow lines in Figure 1. Accordingly, the accurate determination of 'R22' cannot be easily ascertained from ' I col2' and 'U22'. The crosstalk currents alter the measured value of the target element, which in turn affects the stimulus acting on the resistive element to be scanned. To enhance measurement accuracy, a comprehensive analysis and appropriate methodology is required to eliminate crosstalk-induced errors. A zero- potential method (ZPM) schematic (not shown) is used for resistive sensor arrays but suffers from parasitic effects which lead to deterioration of the crosstalk current effect. The aforementioned issues arise due to the following reasons:

1. The crosstalk current effect is significantly contributed by parasitic resistance originating from connection wires and printed circuit board (PCB) wires; and

2. The crosstalk current effect is induced by the offset voltage of the row and column driving amplifiers.

As these issues are intrinsic to the electrical components involved, their elimination poses a significant challenge. To mitigate the aforementioned problems, a Dynamic Zero Current Method (DZCM) circuit schematic has been proposed.

Figure 2 is a circuit diagram 200 illustrating a dynamic zero current method (DZCM) circuit design for a 4 x 4 sensor array, according to an embodiment the present disclosure.

An operational principle of the DZCM schematic 200 involves driving both ends of the adjacent unmeasured resistors to a zero potential. As a result, minimal current flows through these resistors, leading to the cut-off of the crosstalk current path. In the ZPM design, the non-zero current arising from parasitic resistance and amplifier offset voltage causes measurement errors in the low value RSA. To address this issue, the proposed DZCM includes a feedback network within the row driving unit 210 of readout schematic 200, which enforces zero current through each row of the adjacent unmeasured resistors. This feedback mechanism can flexibly adjust the node potential of the array resistors of sensor 220 to match the varying parasitic resistance and amplifier offset voltage in the readout system.

The DZCM circuit design 200 includes a current sensing resistor, denoted as R_sen, which performs the function of converting current to voltage. To amplify the voltage across R_sen, a feedback instrumentation amplifier (FBIA) is employed. The circuit design also features switches denoted as SW1 , which are closed (ON) in rows containing measuring resistors. Additionally, switches denoted as SW are open (OFF) in adjacent unmeasured rows. It should be noted that all amplifiers depicted in Figure 2 are non-ideal.

In the example implementation, a 4 x 4 RSA 220 is provided featuring four row connections and four column connections. To detect the output of the sensors in array 220, a first-row connection is driven to a fixed voltage, and the current on the four column connections is detected following applying the driving voltage to the row connection. This enables the acquisition of the measurement data for the four cells located in the first-row connection, one column at a time. By utilizing this process, four cells in one row can be measured in a single step. Once the results for all the sensors in the first row have been obtained, the procedure is repeated for the second row and so forth until all row connections have been measured. During the scanning of the row of interest in array 220, each resistor located in the scanned row is referred to as a resistive element of interest A (that is being tested) while the resistors in the remaining rows are designated as an adjacent or neighboring resistor R_um which is not being measured.

In example implementations, the read-out circuit 200 includes a row driving unit 210 that is configured to connect a voltage source V_in to multiple rows of the resistive elements of the sensor array 220 for driving the voltage source V_in to a row of the resistive elements. The row driving unit 210 includes switching units SW1 or SW, a plurality of row driving amplifiers, and feedback instrumentation amplifiers FBIAs. Each of the switching units SW1 or SW is capable of performing a switching operation and is selectively coupled to each of the row driving amplifiers. Each of the row driving amplifiers is coupled to each of the FBIAs. The apparatus also includes a column scanning unit 230 for detecting at least one voltage signal of a resistive element. The column scanning unit 230 includes column operational amplifiers, wherein each of the column operational amplifiers is connected to a column of the sensor array.

In one aspect, a resistor is connected between a non-inverting input terminal of each of the plurality of row driving amplifiers and each switching unit SW1 or SW and each of the switching units SW1 or SW are selectively coupled to the row driving amplifiers via the noninverting input terminal according to a first or second state of the switching unit SW1 or SW.

In implementations, the row driving unit 210 further includes a plurality of current sensing resistors R_sen, wherein each current sensing resistor R_sen is coupled to a non-inverting input terminal of each of the plurality of row driving amplifiers and one or more of the FBIAs amplify voltage across one or more of the current sensing resistors R_sen.

The read-out apparatus can reduce parasitic effects attributable to at least one of parasitic resistance from one or more connection or printed circuit board (PCB) wires of the sensor array and an offset voltage applied between the input terminals of the row driving amplifiers.

In implementations, the read-out apparatus may reduce crosstalk current effects associated with reading of a resistive element of interest A in a selected row of the sensor array, wherein the crosstalk current effects are attributable to one or more neighbouring resistive elements R_um arranged in the same column or different row as the resistive element of interest A, wherein the neighbouring resistive elements R_um are not read in association with the reading of the resistive element of interest A. The column scanning unit 230 may further include a plurality of feedback resistive elements, wherein each feedback resistive element is connected between an output terminal of a column operational amplifier and an inverting input terminal of said column operational amplifier, and each of the plurality of column operational amplifiers includes a non-inverting input terminal connected to ground.

In certain embodiments, each column scanning unit 230 outputs an output voltage V_out via each corresponding column operational amplifier. The output voltage V_outof each of the column operational amplifiers may be measured using a multi-meter.

The sensor array can have m number of column connections and n number of row connections and each of the plurality of the resistive elements is connected between a corresponding one of the m column connections and a corresponding one of the n row connections .

In one aspect, the column scanning unit 230 further includes a connection to a plurality of neighbouring resistive elements R_um not read in association with reading of a resistive element of interest A, wherein each neighbouring resistive element R_um is connected to an inverting input terminal of each column scanning unit 230 and a feedback resistive element corresponding to each column scanning unit 230.

The voltage source V_in can be configured to apply a voltage to one or more of the resistive elements of the sensor array 220 via one or more switching units SW1 or SW operating in a first state.

In implementations, the sensor array 220 may be used for sensing microfluidic pressure and each of the resistive elements have a minimum resistance of 10 ohms and a maximum resistance of 200 ohms.

The sensor array 220 can be a resistive sensor array suitable for small-scale electronic devices for replicating the function of human skin.

When reading a resistive element of interest A, zero or negligible current flow can be achieved through each row of a plurality of neighbouring resistive elements R_um associated with the resistive element of interest A. A voltage drop across each of the resistive elements of the sensor array 220 can be adjusted in response to determined parasitic effects attributable to parasitic resistance from one or more connection or printed circuit board (PCB) wires of the sensor array 220 or an offset voltage applied between the input terminals of the row driving amplifiers.

In implementations, the plurality of feedback instrumentation amplifiers (FBIAs) may include an inverting input terminal and an non-inverting input terminal, wherein the non-inverting input terminal is connected to a first end of a first switching unit SW1 and a first end of a first current sensing resistor R_sen, the inverting input terminal is connected to a second end of the first switching unit SW1 and a second end of the first current sensing resistor R_sen, and the first switching unit SW1 and the current sensing resistor R_sen are connected in parallel.

A row of the resistive elements may include at least one resistive element having a first end coupled to one end of a current sensing resistor R_sen and one end of a switching unit SW1 or SW and a second end coupled to one end of a neighbouring resistive element R_um-

The resistive elements of the sensor array 220 may include one or more resistive elements configured to detect a measurable level of voltage, current or resistance value.

Each of the plurality of row driving amplifiers may include a non-inverting input terminal connected to a switching unit SW1 or SW and connected to ground via a single resistor, wherein the non-inverting input terminal is selectively connected to the voltage source V_in based on a state of the connected switching unit SW1 or SW.

Figures 3A and 3B are simplified circuit diagrams 300 and 310 illustrating a zero-potential method (ZPM) and a DZCM circuit design for one unmeasured resistor, according to an embodiment the present disclosure.

In order to expound upon the attributes of the ZPM and DZCM, the present invention discloses simplified network configurations 300 and 310 featuring only one unmeasured resistor, R_um, to demonstrate the parasitic effects attributable to this single resistor. Figure 3 presents the circuit diagram of the simplified model for a) ZPM and b) DZCM, with all amplifiers therein assumed to be ideal.

According to the simplified model 300 of Figure 3A, we can derive the current of R_um for ZPM as:

Equation 1a. Ium - ZMP ^— (Vosi ^— Vos2)/(Rum + R_par)

According to the simplified model 310 of Figure 3B, we can derive the current of R_um for

DZCM as:

—

Equation

In the present invention, the currents of the unmeasured resistor for the Zero-Point Module (ZPM) and Dual-Zero-Current Module (DZCM) are designated as lum-zpivi and lum-DzcM, respectively. The expressions for these currents are provided in Equations 1a and 1 b accordingly. The offset voltages of the row and column driving amplifiers are represented by V_osi and V_Os2, respectively. Additionally, the parasitic resistance of the row and column wires is denoted by R_par, while the resistance of the current sensing resistor is represented by R_sen. The gain of the Feedback Input Amplifier (FBI A) is expressed as Af, and the current of the sensing resistor is designated as l_sen.

From Equation 1a for the ZPM and Equation 1 b for the DZCM, it is evident that l _Um-DzcM computed from Equation 1b is comparatively smaller than l_Um-zpM in Equation 1a due to the presence of the Rsen (1 + Af) term in the denominator.

One example embodiment for calculating measurement errors assumes Af = 1000, R_sen = 1.0 W, Rum = 10.0 W, Rpar = 1.0 W, and R_a = R_b = 1.0 kW, with Vos1 = 1.00 mV and Vos2 = - 1.00 mV. Subsequently, Equation 1a yields l_Um-zpM = 0.18 mA for the ZPM, while Equation 1 b yields lum-DzcM = 0.0019 mA for the DZCM. In this example calculation, the negative feedback in the DZCM circuit, as a result of V_osi, V_0S2, and R_par, reduces its parasitic effect current to 1% of the parasitic effect current in the ZPM circuit. As such, DZCM minimizes measurement errors in low value RSA to a great extent.

Figure 4 is a simplified circuit diagram 400 illustrating a DZCM circuit model for a 2 x 2 sensor array including parasitic effects and crosstalk current effects, according to an embodiment the present disclosure.

In order to assess the crosstalk current impact in the DZCM, a 2 x 2 array is derived from a 4 x 4 array through further simplification, as exemplified in Figure 4. The reduced array network 400 incorporates a parasitic effect 410 caused by V_osi, V_0S2, and R_par. Based on the preceding discussion and Equation 1a and Equation 1b, the crosstalk currents 420 of the adjacent unmeasured resistors R21 and R22 in the DZCM represent only 1% of those in the ZPM. Therefore, the crosstalk current effect 420 from R21 and R22 in the DZCM is deemed trivial and negligible. Notably, R21 and R22 illustrated in Figure 4 and can be safely disregarded when deriving the Equation 2 formula below.

Based on the simplified circuit diagram 400 of Figure 4, the following equations can be derived:

Equation 2a. Va ⁼ Vos21 + If1 Rpar ⁼ Vos21 + I n Rpar

Equation 2b. Vb ⁼ Vos11 + Vjn ■ IbRpar ⁼ Vos1 1 + Vjn ■ (I11 + l l 2) Rpar

Equation 2c. Vp ^> taRpar + Vos22 ^— I ^Rpar + Vos22

Equation 2d: Vb - V_a = I 11 R11

Equation 2e: Vb - Vd = 112R12

The Kirchhoff's law circuit diagram 500 depicted in Figure 5 is employed to examine the DZCM network 400 presented in Figure 4.

In order to simplify calculation, we hypothesize that R11 = Rx, R12 = Rum and 10*Rpar < Rum ~ Rx. After substituting equations 2a, 2b, 2c with equations 2d, 2e, we obtain Equation 3:

Equation 3a

Equation 3b

Equation 3 is a non-homogeneous linear equation R l = V and after several solving steps, we derived the crosstalk current effect at Vos12 as:

— .. . equation 4:

As Rpar « Rum ~ Rx, we can simplify Equation 4 as:

Equation

However, if we assuming Rpar « Rum ~ Rx, then for a ZPM 2 x 2 array circuit model including the parasitic and crosstalk effects, we derive the following equation for crosstalk current effect:

E Uation

It is evident that Equation 5 exhibits similarities with Equation 6, albeit being devoid of the

■ i.i , . . . .- .■ « , variable which is present in Equation 6. This absence of

Equation 5 leads to a lower error resulting from Vos12 as compared to Equation 6, thereby yielding a favorable outcome with respect to the DZCM array network.

We now turn to the description of various experiments used to evaluate embodiments of the disclosure. Some of these illustrate embodiments of the disclosure other than those discussed above.

A number of experiments have been devised to assess the performance of the ZPM and DZCM under optimal conditions. The experimental configurations are illustrated in Table 1.

Table 1. Experiments configuration for DZCM with selected combinations

The measurement result from a multimeter of an ideal single resistor is represented as R_id. Meanwhile, the output amplifier’s voltage of array resistors is measured as V_out by a multimeter. We can obtain the resistance value of the resistor of interest, R_x using the following equation The measurement percentage error between RM and R_x

is evaluated as follows

Experiment (EXP) A analyzes the effect of R_x on e% in arrays of various sizes when the unmeasured array resistors R_um are fixed at their lower and upper limits (i.e. , 1 Q and 200 Q, respectively) and R_par and v_os are set to zero.

EXP B analyses the effect of unmeasured array resistors R_um on e% in the simplest 2 x 2 array, as R_x increases and R_par and v_os are zero.

EXP C analyses the effect of parasitic resistance of column and row (R_paicoi and R_parR_Ow) on e% when the unmeasured array resistors R_um and R_x are fixed at 1 Q (V_in = 10 mV), 50 Q (Vin = 100 mV), 200 Q (V_in = 1000 mV) and offset voltage v_os is zero. The reason for increasing V_in with increasing R_um and R_x is to avoid the crosstalk current effect, which will surpass the signal current of R_x if V_in is fixed to 10 mV and R_x increases to 50 Q or 200 Q.

The array size is set to 6 x 6 and 12 x 12.

EXP D analyses the effect of v_os on e% when the unmeasured array resistors R_um and R_x are fixed at 1 Q (Vin = 10 mV), 50 Q (Vin = 100 mV), 200 Q (Vin = 1000 mV) and R_par is set to zero. The array size is set to 6 x 6 and 12 x 12.

Experimental Results for DZCM with Ideal Resistors

EXPERIMENT A:

Figures 6A and 6B are graphs illustrating an effect of a resistor of interest (R_x) on a measurement error of various Sensor array sizes (SAR) with an unmeasured resistor (R_um) is set at 200 ohms and 1 ohm respectively for a DZCM and ZPM circuit design, according to an embodiment the present disclosure.

As shown in Figure 6A, with R_um = 200 Q:

The measurement errors of the DZCM and ZPM are found to be comparable when R_x falls within the range of 1 Q to 10 Q. There is no significant improvement on the system performance by the additional feedback network of the DZCM in this R_x range.

As shown in Figure 6B, with R_um = 1 0:

An e% of the DZCM is smaller than that of the ZPM within the R_x range of 1 Q to 10 Q, showing the advantage of the DZCM feedback network in bringing down the crosstalk current.

In summary, Figures 6A and 6B illustrate an improvement of the DZCM in reducing measurement error in the range of 1 Q < R_x < 10 Q and R_um = 1 Q. That is to say, in low resistance RSA, the DZCM is capable of decreasing the measurement error.

EXPERIMENT B:

As shown in Figure 7, the e% of the DZCM is smaller or similar to the ZPM in the range of 1 Q < R_x < 10 Q

EXPERIMENT C:

Figures 8A-8F are graphs illustrating the effect of a parasitic resistance (R_par) of both row and column wires, the effect of a parasitic resistor of column wires (R_parCoi), and the effect of a parasitic resistor of row wires (R_parR_OW) on the measurement error of various Sensor array sizes (S_ar) set to 6 x 6, 12 x 12 when a resistor of interest (R_x) is set to an unmeasured Resistor (R_um) of 1 ohm, 50 ohms, and 200 ohms, according to an embodiment the present disclosure.

As shown in Figures 8A, 8B, and 8C when R_parR_Ow (the parasitic resistor of row wires) changes from 0 Q to 3.5 Q and R_Um = R_x = 1 O, 50 Q, 200 Q, the R_x error of the ZPM is the same as in the DZCM.

When parcoi (the parasitic resistor of column wires) changes from 0 Q to 3.5 Q, R_um = R_x = 1 Q, 50 Q, 200 Q, as demonstrated in Figures 8D, 8E, and 8F the Rx error of the ZPM is higher than that of the DZCM. The larger array size results in a greater error difference between the ZPM and DZCM. This error difference increases as R_parcoi goes up. This is due to the presence of the negative feedback network in the DZCM that effectively reduces the parasitic effect of R_par in the low resistance domain.

EXPERIMENT D:

Figures 9A-9F are graphs illustrating the effect of an offset voltage of column amplifiers (Vosc) or offset voltage of row amplifiers (VOSR) on measurement errors of various Sensor array sizes (S_ar) set to 6x6, 12x12, when a resistor of interest (R_x) is set to an unmeasured Resistor (R_um) of 1 ohm, 50 ohms, and 200 ohms, according to an embodiment the present disclosure.

To analyse the system performance with regard to offset voltage, error variation is preferred over absolute error. Absolute error, as discussed in EXPERIMENT A, can be nulled by manual operation. On the other hand, the fluctuation of e% is non-zero, as v_osc (offset voltage of column amplifiers) and V_OSR (offset voltage of row amplifiers) change. This inconstancy of measurement error often results in temperature drift and process variation of amplifier chips.

Offset voltages exist across the rows and columns in RSA. In the experiment to examine the effect of Vosc, v_0SR is kept constant at zero and v_osc changes from -3 mV to 3 mV in steps of 1 mV. Similarly, for the second study to evaluate the influence of V_OSR, V_OSC is fixed to zero and v_0SR is varied from -3 mV to 3 mV in steps of 1 mV. The offset voltages V_OSR and v_osc are applied to the positive inputs of all row and column amplifiers, labelled as v_osi and v_0S2, respectively (see Figures 3A and 3B). Error variation is defined as the difference in measurement error associated with experimental conditions.

As seen in Figures 9A-9E, when v_osc and V_OSR change from -3 mV to +3 mV with 1 mV steps, the DZCM (the curve with solid dots) has lower R_x error variation than the ZPM (the curves with open dots) in all array sizes. This reveals that the DZCM is capable of eliminating the adverse effects arising from v_0SR and v_osc of row/column amplifiers. Such improvements can be proven in Equation (5) and Equation (1b) above, respectively. The DZCM Equation (5) has one less item than ZPM Equation (6). That is because, from Equation (5), the presence of Af in the DZCM feedback network helps to reduce the effect of offset voltage on the error measurement.

As seen in Figure 9F, when V_OSR changes from -3 mV to +3 mV with 1 mV steps, the DZCM has larger R_x error variation than the ZPM in all array sizes. This reveals that the DZCM is not suitable for high value RSA. However, the error gaps between the DZCM and ZPM decrease with array size increases. This implies the DZCM will have better performance when the high value RSA has a larger array size.

These performances are illustrated in Table 2:

Table 2: Rx error variation by Vosr, Vosc with SAR = 6 x 6 and 12 x 12

Figure 10 is a block diagram showing the technical architecture 1000 of a sensing device and/or a control device corresponding to the sensing device for implementing some or all of the circuit schematics of Figures 1-5 for performing a readout of the sensor array.

For example, the control device may include a server, a cloud computing device, a wearable device, and/or the like and may receive data from and/or transmit data to another device such as the sensing device. The sensing device may include multiple sensor elements (e.g. an array of sensor elements) with each element configured to measure voltage information. The sensing device may further include an integrated readout circuit such as the example DZCM circuit design described above with respect to Figure 2. The sensing device may utilize a plurality of sensor technologies such as a charge-coupled device (CCD) technology and complementary metal-oxide-semiconductor (CMOS) technology.

The technical architecture includes a processor 1022 (which may be referred to as a central processor unit or CPU) that is in communication with memory devices including secondary storage 1024 (such as disk drives), read only memory (ROM) 1026, random access memory (RAM) 1028. The processor 1022 may be implemented as one or more CPU chips. The technical architecture may further comprise input/output (I/O) devices 1030, and network connectivity devices 1032.

The secondary storage 1024 is typically comprised of one or more disk drives or tape drives and is used for non-volatile storage of data and as an over-flow data storage device if RAM 1028 is not large enough to hold all working data. Secondary storage 1024 may be used to store programs which are loaded into RAM 1028 when such programs are selected for execution.

In this embodiment, the secondary storage 1024 has an order processing component 1024a comprising non-transitory instructions operative by the processor 1022 to perform various operations of the method of the present disclosure. The ROM 1026 is used to store instructions and perhaps data which are read during program execution. The secondary storage 1024, the RAM 1028, and/or the ROM 1026 may be referred to in some contexts as computer readable storage media and/or non-transitory computer readable media.

I/O devices 1030 may include printers, video monitors, liquid crystal displays (LCDs), plasma displays, touch screen displays, keyboards, keypads, switches, dials, mice, track balls, voice recognizers, card readers, paper tape readers, one or more different sensors such as touch sensors, force sensors, motion sensors, temperature sensors, and biological sensors or other well-known input devices.

The processor 1022 executes instructions, codes, computer programs, scripts which it accesses from hard disk, floppy disk, optical disk (these various disk-based systems may all be considered secondary storage 1024), flash drive, ROM 1026, RAM 1028, or the network connectivity devices 1032. While only one processor 1022 is shown, multiple processors may be present. Thus, while instructions may be discussed as executed by a processor, the instructions may be executed simultaneously, serially, or otherwise executed by one or multiple processors.

Although the technical architecture is described with reference to a single control device or sensing device, it should be appreciated that the technical architecture may be formed by two or more devices in communication with each other that collaborate to perform a task. For example, but not by way of limitation, an application may be partitioned in such a way as to permit concurrent and/or parallel processing of the instructions of the application. Alternatively, the data processed by the application may be partitioned in such a way as to permit concurrent and/or parallel processing of different portions of a data set by the two or more devices. In an embodiment, virtualization software may be employed by the technical architecture 1000 to provide the functionality of a number of servers that is not directly bound to the number of devices in the technical architecture 1000. In an embodiment, the functionality disclosed above may be provided by executing the application and/or applications in a cloud computing environment. Cloud computing may comprise providing computing services via a network connection using dynamically scalable computing resources. A cloud computing environment may be established by an enterprise and/or may be hired on an as-needed basis from a third-party provider.

By programming and/or loading executable instructions onto the technical architecture, at least one of the CPU 1022, the RAM 1028, and the ROM 1026 are changed, transforming the technical architecture in part into a specific purpose machine or apparatus having the novel functionality taught by the present disclosure. It is fundamental to the electrical engineering and software engineering arts that functionality that can be implemented by loading executable software into a computer can be converted to a hardware implementation by well-known design rules.

Whilst the foregoing description has described exemplary embodiments, it will be understood by those skilled in the art that many variations of the embodiment can be made within the scope and spirit of the present invention.

Claims

Claims:

1. A read-out apparatus comprising: a sensor array comprising a plurality of resistive elements; and a row driving unit electrically coupled to a voltage source to a plurality of rows of the resistive elements of the sensor array for driving the voltage source to a row of the plurality of rows of the resistive elements, wherein the row driving unit comprises a plurality of switching units, a plurality of row driving amplifiers, and a plurality of feedback instrumentation amplifiers (FBIAs), wherein each of the switching units performs a switching operation and is selectively electrically coupled to each of the row driving amplifiers and each of the row driving amplifiers is coupled to each of the FBIAs.

2. The read-out apparatus of claim 1, wherein a resistor is electrically coupled between a non-inverting input terminal of each of the plurality of row driving amplifiers and each switching unit and each of the switching units are selectively electrically coupled to the row driving amplifiers via the non-inverting input terminal according to a first or second state of the switching unit.

3. The read-out apparatus of claim 1 or 2, wherein the row driving unit further comprises a plurality of current sensing resistors, wherein each current sensing resistor is electrically coupled to a non-inverting input terminal of each of the plurality of row driving amplifiers and one or more of the FBIAs amplify voltage across one or more of the current sensing resistors.

4. The read-out apparatus of any preceding claim, wherein parasitic effects attributable to at least one of parasitic resistance from one or more connection or printed circuit board (PCB) wires of the sensor array and an offset voltage applied between the input terminals of the row driving amplifiers is reduced.

5. The read-out apparatus of any preceding claim, wherein crosstalk current effects associated with reading of a resistive element of interest in a selected row of the sensor array is reduced, wherein the crosstalk current effects are attributable to one or more neighbouring resistive elements arranged in the same column or different row as the resistive element of interest, wherein the neighbouring resistive elements are not read in association with the reading of the resistive element of interest.

6. The read-out apparatus of any preceding claim, further comprising a column scanning unit for detecting at least one voltage signal of a resistive element from the plurality of resistive elements, wherein the column scanning unit comprises a plurality of column operational amplifiers, wherein each of the column operational amplifiers is electrically coupled to column of the plurality of columns of the sensor array, and a plurality of feedback resistive elements, wherein each feedback resistive element is electrically coupled between an output terminal of a column operational amplifier and an inverting input terminal of said column operational amplifier, and each of the plurality of column operational amplifiers includes a non-inverting input terminal connected to ground.

7. The read-out apparatus of any preceding claim, wherein the sensor array has m number of column connections and n number of row connections and each of the plurality of the resistive elements is connected between a corresponding one of the m column connections and a corresponding one of the n row connections.

8. The read-out apparatus of any preceding claim, wherein a column scanning unit further comprises a plurality of neighbouring resistive elements not read in association with reading of a resistive element of interest, wherein each neighbouring resistive element is electrically coupled to an inverting input terminal of each column scanning unit and a feedback resistive element corresponding to each column scanning unit.

9. The read-out apparatus of any preceding claim, wherein the voltage source is configured to apply a voltage to one or more of the resistive elements of the sensor array via one or more switching units operating in a first state.

10. The read-out apparatus of any preceding claim, wherein the sensor array is used for sensing microfluidic pressure and each of the resistive elements have a minimum resistance of 10 ohms and a maximum resistance of 200 ohms.

11. The read-out apparatus of any preceding claim, wherein the sensor array is a resistive sensor array suitable for small-scale electronic devices for replicating the function of human skin.

12. The read-out apparatus of any preceding claim, wherein zero or negligible current flow through each row of a plurality of neighbouring resistive elements associated with a resistive element of interest when reading the resistive element of interest is achieved.

13. The read-out apparatus of any preceding claim, wherein a voltage drop across each of the resistive elements of the sensor array is adjusted in response to determined parasitic effects attributable to parasitic resistance from one or more connection or printed circuit board (PCB) wires of the sensor array or an offset voltage applied between the input terminals of the row driving amplifiers.

14. The read-out apparatus of any preceding claim, wherein at least one of the plurality of feedback instrumentation amplifiers (FBIAs) comprises an inverting input terminal and an non-inverting input terminal, wherein the non-inverting input terminal is electrically coupled to a first end of a first switching unit and a first end of a first current sensing resistor, the inverting input terminal is electrically coupled to a second end of the first switching unit and a second end of the first current sensing resistor, and the first switching unit and the current sensing resistor are electrically coupled in parallel.

15. The read-out apparatus of any preceding claim, wherein the row of the resistive elements comprises at least one resistive element having a first end electrically coupled to one end of a current sensing resistor and one end of a switching unit and a second end electrically coupled to one end of a neighbouring resistive element.

16. The read-out apparatus of any preceding claim, wherein the resistive elements of the sensor array comprise one or more resistive elements configured to detect a measurable level of voltage, current or resistance value.

17. The read-out apparatus of any preceding claim, wherein each of the plurality of row driving amplifiers includes a non-inverting input terminal electrically coupled to a switching unit and electrically coupled to ground via a single resistor, wherein the non-inverting input terminal is selectively electrically coupled to the voltage source based on a state of the electrically coupled switching unit.

18. The read-out apparatus of any preceding claim wherein an output of each of the plurality of FBIAs is electrically coupled to an inverting input terminal of each of the row driving amplifiers via a first resistor and the inverting input terminal is further electrically coupled to an output of each of the row driving amplifiers via a second resistor, wherein the first and second resistor are electrically coupled in series between the output of each FBIA and the output of each row driving amplifier.

19. A non-transitory computer readable medium comprising executable instructions when executed by one or more computers cause the one or more computers to measure a voltage value of a resistive element of a sensor array using a read-out apparatus, the read-out apparatus comprising: a sensor array comprising a plurality of resistive elements arranged in a plurality of rows and columns; and a row driving unit electrically coupled a plurality of rows of the resistive elements of the sensor array to a voltage source for driving the voltage source to a row of the plurality of rows of the resistive elements, wherein the row driving unit comprises a plurality of switching units, a plurality of row driving amplifiers, and a plurality of feedback instrumentation amplifiers (FBIAs), wherein each of the plurality of switching units performs a switching operation and is selectively coupled to each of the plurality of row driving amplifiers and each of the row driving amplifiers is coupled to each of the plurality of FBIAs.

20. A method for using a read-out apparatus for measuring a voltage value of a resistive element, the method comprising: arranging a plurality of resistive elements of a sensor array; connecting electronically a plurality of rows of the resistive elements of the sensor array to a voltage source via a row driving unit for driving the voltage source to a row of the plurality of rows of the resistive elements, wherein the row driving unit comprises a plurality of switching units, a plurality of row driving amplifiers, and a plurality of feedback instrumentation amplifiers (FBIAs), wherein each of the switching units is selectively coupled to each of the plurality of row driving amplifiers and each of the row driving amplifiers is coupled to each of the plurality of FBIAs; and performing a switching operation via the plurality of switching units.