Generic RS485 4-20mA Output Soil Sensor with 2M Cable 3-Pin Probes - Temperature + Humidity

The 4-20mA output is an analog current loop where the measured value (e.g., moisture or temperature) is represented by a proportional current between 4mA (minimum) and 20mA (maximum). It is simple, noise-resistant, and ideal for single-sensor connections to PLC analog inputs. The RS485 output is a digital, serial communication interface (typically using Modbus RTU protocol) that allows multiple sensors to be daisy-chained on a single bus, enabling addressable, multi-point data collection from a single host port.

For the 4-20mA loop, you will need a DC power supply (typically 12-24V DC) to power the transmitter circuit. Connect the positive supply to the sensor's power input, and the sensor's current output signal wire to your data acquisition device's analog input. A 250-ohm precision resistor is usually placed across the input terminals of your DAQ system to convert the 4-20mA current into a 1-5V voltage signal for measurement. Always ensure the loop power supply voltage is within the sensor's specified range.

Yes, the probe end is designed for direct insertion into the soil profile. Ensure the cable gland or connection point where the cable meets the probe body remains above ground or is properly sealed to prevent water ingress. For long-term installation, it is recommended to install the sensor at the desired root zone depth and backfill firmly to ensure good soil-to-sensor contact for accurate moisture readings.

While specific accuracy figures depend on soil type and calibration, typical volumetric water content range is 0-100% with an accuracy of ±3-5% after soil-specific calibration. The temperature measurement range is typically -40°C to +80°C with an accuracy of ±0.5°C. For precise agronomic use, field calibration against gravimetric soil samples is recommended to establish a site-specific calibration curve.