Capacitive Soil Moisture
This analog capacitive soil moisture sensor measures soil moisture by detecting the change in capacitance that stems from the moisture content of the surrounding soil. The output of the sensor is a voltage between 0V and 3V, with 0V being very dry soil and 3V being wet soil.
MQ4 Methane Gas
The MQ4 module allows the JackBord to detect methane gas at concentrations from 300 ppm to 10,000 ppm. The reading output from the sensor is an analog voltage from 0.1V to 4.5V. There is a digital output as well, pin DO, which is normally high and goes low when gas is detected.
Short Range Proximity
This sensor uses an infrared transmitter and receiver to gauge the distance between the sensor and an object near it. It has a digital and an analog output which can be used to control things in response to the presence or absence of an object.