The slow changes in the output voltage of the previous circuit (MEC193E) are not appropriate for drive logic circuits that use TTL or CMOS technologies and microcontrollers. The block shown in Figure 1 adds a necessary snap action to resistive sensors, allowing them to better drive logic functions.
For CMOS applications, the gate can be one of the four existing in the 4093 IC. For TTL applications, the 7404 IC can be used. For CMOS applications where the sensitivity is higher (due to the high-impedance inputs), the potentiometer must be 2 to 4 times the resistance of the sensor under normal conditions, with a maximum value of 2.2 MΩ. For TTL, the same is valid, but the upper resistance limit is about 47 kΩ due the sensitivity, which is lower than that of the CMOS gates.
