Hardware Techniques for Improving the Calibration Performance of Direct Resistive Sensor-to-Microcontroller Interface

Abstract

Direct sensor-to-microcontroller is a simple approach for direct interface of passive modulating sensors to a microcontroller without any active components in between the sensor and the microcontroller and without an analog to digital converter. The metrological performances of such interface circuits are limited by certain microcontroller parameters which are predetermined by the manufacturing technology. These limitations can be improved by specific hardware-related techniques and can improve the accuracy, speed and resolution of the measurements. Such hardware solutions as well as proper selection of the electrical components are addressed in this paper. It has been shown that employment of only a few MOSFET transistors can reduce the maximal relative error of single point calibration more than fifteen times and can increase the measuring speed around 30 % in all calibration techniques in the measurement range of PT1000 resistive temperature sensors. Moreover, the effective number of resolution bits increases by more than 1.3 bits when using an external comparator.

Low-Power Direct Resistive Sensor-to-Microcontroller Interfaces

“…Fig. 14 shows that the energy consumption is minimum for these values and that the experimental results fit the theoretical results predicted by (15).…”

“…The proposed design procedure and energy consumption model (15) were validated for two different design scenarios. One of them uses a sensor resistance much lower than R μ and the other uses a larger one.…”

“…For these measurements, the watch-dog timer period was changed to 15.625 ms to improve the measuring accuracy of I cc and the switch S1 was connected to 1. These measurements were also performed for C c = 0 μF to determine that Q (3) is 440 nC (15).…”

“…Note that (3) does not depend on C c , R p and V TL , and hence, the accuracy in measuring R m is not limited by their tolerances nor their temperature drifts. Other limiting factors and their impact on the system performances have been analyzed in [15], where suggestions can also be found to improve the system performances.…”

An Implementation of a Compact Smart Resistive Sensor Based on a Microcontroller with an Internal ADC

“…Obviously, this problem was resolved by extension of the direct sensor-tomicrocontroller interface circuit with additional components, e.g. a calibration resistor [16], MOSFET transistors [17], or also an inverter consisted of two MOSFET transistors [18].…”