Improved Calibration Method for Resistive Sensors Using Direct Interface Circuits

Two-Capacitor Direct Interface Circuit for Resistive Sensor Measurements

“…Finally, the two capacitors in the TCDIC could also be used in a classic DIC based on the three-signal auto-calibration technique [ 34 ]. Similarly, the TCDIC may be compatible with other circuits designed to obtain different improvements in the characteristics of a resistive DIC, such as those shown in References [ 14 , 29 , 31 , 32 , 33 ], meaning that these circuits could also have benefits provided by the TCDIC.…”

“…The non-linearity of the resistors of the PDD buffers may also affect the estimates. In this case, the solution described in the literature is to use a calibration resistor in addition to those shown in Figure 1 [ 31 ]. In contrast, one of the problems for high resistance values is an excessive discharge time.…”

Reducing Measurement Time in Direct Interface Circuits for Resistive Sensor Readout

“…A second variant of the TPCM, Figure 1c, uses an additional calibration resistor, RC3, whenever low RS measurements are needed. This means the circuit requires an additional charge and discharge process, but it allows RS to be determined with 10 times greater precision if its value is around 10 Ω [15]. Discharging through R C1 and R C2 instead of through R S achieves times T Rc1 and T Rc2 , replacing R S with R C1 and R C2 in Equation (2).…”

“…Such simplicity means that this type of circuit is particularly suited for portable applications, where both the number of components and their consumption are very important. DICs are also highly versatile in terms of the PDDs used, allowing the use of both microcontrollers [4][5][6][7][8][9][10] and field-programmable gate arrays (FPGAs) [11][12][13][14][15][16]. The calculation capabilities of a PDD connected to a DIC allow them to function as smart sensors, pre-processing information from the sensor and thus reducing the workload in subsequent high-level processing and decision stages [17].…”

“…Several issues need to be considered when designing a resistive DIC, such as accuracy, uncertainty, resolution [6,8,16,[20][21][22], and calibration points [23]. Other problems that may influence the performance of these circuits such as response to dynamic signals [24], lead wire resistance [25], power consumption [5], estimation time [13], or problems related to the measurement of low-resistance sensors [15], have also been addressed.…”