Sensors Used to Determine Physical Soil Properties

Ovidiu Marian, Mircea Muntean, Ovidiu Ranta, Adrian Molnar, Valentin Crişan

Abstract


Determining soil properties in the shortest possible time is no longer a challenge at present. Among the soil properties
that can be determined relatively quickly can be mentioned: humidity, pH, soil respiration, enzymatic activity, existing gas
determination, nutrient requirements, etc. Soil humidity can be determined using capacitive sensors (an air-filled condenser
can serve as a relative humidity sensor because soil humidity modifies the electrical permissiveness of the air), resistive
sensors (it contains a relatively low resistivity material that changes significantly in various humidity conditions), hybrid
sensors (measures both the capacity and the electrical conductivity of the soil). To determine the soil pH it can be used the
color-changing indicator strip, pH indicator fluid and pH sensor (the principle of measurement is based on the fact that the
two-fluid interface produces a measurable electrical potential). Determination of soil respiration is carried out by special
devices called breathing chambers in which CO
2
 sensors are introduced: sensors for determining the CO
2
 flux through
thermal conductivity, solid-state electrochemical sensors, sensors made of different oxide mixtures, membrane sensors
selective ions and optical sensors. Enzymatic sensors are used to identify and quantify enzymatic activity. The sensor is a
heated sample, an electrochemical sensor or an optical sensor. The basic operating principle is that an enzyme is fixed to a
layer in which the substrate is dispersed. The olfactory sensor or electronic nose is less a sensor or instrument and more a
measurement strategy. All methods of odour measurement can be divided into four groups: instrumental analysis,
semiconductor gas sensors, potential difference membrane sensors and quartz microbalance method

Keywords


humidity, pH, enzymatic sensor, electronic nose, N-sensors.

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