3.3 Liquid Detection Threshold

A configurable threshold mechanism for liquid detection is implemented in the MTCH9010 liquid detector. This configurable parameter can be provided through a voltage signal connected to the analog input pin THR or by using the Enhanced Configuration.

Several factors influence the measurements and create the need for a configurable threshold for liquid detection:

Sensor design and dimensions
Liquid properties
Sensitivity requirements for the application
Environmental temperature and humidity

The threshold value is computed according to the following equations by configuring the liquid detection threshold through the THR analog input pin:

If the operation mode is configured as a Capacitive detection method, the following equation is used for the threshold:
${threshold}^{} = \frac{referenceValue \times adcStandardMeas}{65535} \times \frac{20}{100}$
If the operation mode is configured as a Conductive detection method, the following equation is used for the threshold:
${threshold}^{} = referenceValue + \frac{adcStandardMeas \times (65535 - referenceValue)}{65535}$

Note: The reference value is represented by an average of measurements using the sensor in a dry state.

The voltage signal used as input for the THR pin must be within the range of 0V and V_DD. The following table shows the correlation between the THR voltage and the liquid detection threshold level:

Table 3-3. Liquid Detection Threshold Settings
Input Range	Liquid Detection Threshold
Input Range	Capacitive Operation Mode	Conductive Operation Mode
0V to V_DD	Lowest at 0V Increases with voltage on the THR pin Highest at V_DD (20% of the reference value)	Reference value at 0V Increases with voltage on the THR pin Highest at V_DD