A new gas sensor electronic interface with generalized impedance converter

Circuit Topologies for MOS-Type Gas Sensor

“…In [21], the sensor resistance range is between 500 Ω and 30 kΩ, but the range is wider in in this proposal, from 500 Ω to 100 kΩ. Due to this, some changes in the topology were introduced.…”

“…On one hand, the capacitor C3 of the Figure 5 changes its place for the resistance R5, and to grow their values until 33 nF and 15 kΩ; this change does not affect to the theoretical behavior of the GIC [27], but the maximum voltage drop is only 3 V in the worst case. On the other hand, our design has higher voltages than the voltages used in the original paper; this is due to two reasons: the first reason is that the change in the resistance range of the sensor increases the voltage needed; and the second reason is that in [21] a microcontroller PSoC was used simulating a timer 555, with power voltage level of 3.3 V, whereas in our design a 555 timer integrated circuit [26] is used with a minimum power voltage of 5 V.…”

“…This topology is based on the use of a simulated capacitance using a Generalized Impedance Converter (GIC). The capacitance changes linearly with the sensor resistance; an oscillator is created using a 555 timer with a frequency that depends on the simulated capacitance [21]. This topology theoretically has a linear dependence between the sensor resistance and the oscillator frequency, like the Anderson loop.…”

“…The last topology was proposed in [21], and it is based on the simulation of a capacitance using the Generalize Impedance Converter. In addition, a 555 timer is used in a stable mode to obtain a signal whose frequency changes linearly with the sensor resistance [26].…”

“…Electronics 2020, 9, x FOR PEER REVIEW 6 of 18 Figure 5. Design of the paper in which is based the design of the converter resistance-to-frequency [21].…”