NBL-S-TMC Soil Temperature, Moisture and EC Sensor

The NiuBoL NBL-S-TMC is a 3-in-1 soil sensor designed to measure soil temperature, soil moisture and electrical conductivity (EC) from one probe. It is suitable for irrigation, fertigation, greenhouse cultivation, soil salinity monitoring, precision agriculture, research and agricultural IoT systems.

The soil moisture channel uses FDR (Frequency Domain Reflectometry) technology, while the electrical conductivity channel uses an AC bridge measurement method. The sensor integrates all three parameters into one IP68 probe and transmits measurement data through RS485 Modbus RTU.

The three measurements provide complementary information about root-zone conditions. Soil moisture indicates water availability, soil temperature provides thermal context, and EC reflects the overall conductivity produced by soluble ions and salts in the soil solution.

Soil EC does not identify individual nutrients. An EC measurement cannot independently determine nitrogen, phosphorus or potassium concentrations because many different dissolved ions contribute to electrical conductivity.

NBL-S-TMC Soil Temperature, Moisture and EC Sensor Technical Specifications

Note: Product configuration, power supply and cable length can be selected according to project requirements.

Three Soil Parameters in One Probe

The NBL-S-TMC combines three root-zone measurements that are particularly useful for irrigation, fertigation and salinity monitoring.

Soil Temperature

Soil temperature influences seed germination, root activity, microbial activity and nutrient processes in the root zone. Temperature measurement also provides useful context when interpreting moisture and EC data.

Soil Moisture

Soil moisture indicates the water condition around the crop root zone. The NBL-S-TMC uses FDR technology to determine soil moisture from changes in the dielectric properties of the surrounding soil.

Soil Electrical Conductivity

Soil EC measures the electrical conductivity produced by dissolved ions in the soil solution. It is influenced by soluble salts, fertilizer concentration, irrigation water, soil moisture, temperature and soil characteristics.

What Does Soil EC Measure?

Electrical conductivity indicates how easily electrical current passes through the soil solution. Dissolved ions such as salts and fertilizer ions increase the conductivity of the solution.

Soil EC monitoring can help identify:

• Changes in soluble salt concentration

• Fertilizer accumulation trends

• Root-zone salinity conditions

• Changes before and after irrigation

• Differences between cultivation zones

• Fertigation-related conductivity trends

EC is not a direct nutrient analysis. The same EC value can result from different combinations of dissolved ions. Individual nutrient concentrations require appropriate nutrient-specific or laboratory analysis.

Soil EC vs NPK

The NBL-S-TMC provides soil EC as an independent measurement channel. It does not output nitrogen, phosphorus or potassium values.

How Does FDR Soil Moisture Measurement Work?

The soil moisture channel uses FDR (Frequency Domain Reflectometry) technology.

The probe generates an electromagnetic field around the sensing electrodes and measures the dielectric response of the surrounding soil. Water has a significantly higher dielectric constant than air and dry soil material, so changes in soil water content produce measurable changes in the dielectric response.

The sensor electronics process this response and convert it into a volumetric soil moisture percentage.

How Does Soil EC Measurement Work?

The EC channel uses an AC bridge measurement method. The electrodes measure the electrical conductivity generated by soluble ions in the soil or other suitable measured medium.

Because conductivity changes with temperature, the NBL-S-TMC includes built-in EC temperature compensation over a 0–50°C compensation range.

Why Soil Moisture Affects EC Measurement

Soil conductivity depends on dissolved ions and the water pathways that allow electrical current to move between the electrodes. Very dry soil can therefore produce EC values that are less representative of the soluble salt condition of the root zone.

When volumetric soil moisture is above approximately 20%, dissolved ions can form a more continuous conductive pathway in the soil, making EC readings more representative of soluble salt conditions.

The 20% value should be treated as a measurement reference rather than a universal irrigation threshold. Soil texture, crop type, substrate, irrigation method and monitoring objectives should also be considered when interpreting EC data.

For trend monitoring, measurements collected under reasonably consistent soil-moisture conditions provide better comparability over time.

NBL-S-TMC Structure and Dimensions

The sensor uses three corrosion-resistant electrodes and a sealed epoxy housing designed for direct contact with soil, substrates and suitable conductive media.

For soil measurement, all three electrodes should be inserted fully into the measured medium and kept in close contact with the surrounding soil.

RS485 Modbus Communication

The NBL-S-TMC supports RS485 Modbus RTU and can connect to compatible PLCs, RTUs, agricultural data loggers and IoT gateways.

NBL-S-TMC Modbus Measurement Data

The RS485 sensor returns three measurement values for soil temperature, moisture and electrical conductivity.

Example measurement values:

RS485 Wiring

Installation note: Wiring should follow the identification supplied with the sensor, especially where customized cables or connectors are used.

How to Install the Soil EC Sensor

Quick Field Measurement

Select a representative measurement location and avoid stones, large roots and other hard objects.

Insert all three electrodes fully into the soil and maintain close contact between the electrodes and the surrounding soil. Avoid rocking the sensor from side to side because this can create air gaps around the probes.

For representative field measurements, several readings can be taken within a small area and compared or averaged where appropriate.

Long-Term Buried Installation

For continuous monitoring, dig to the required measurement depth and insert the sensor horizontally into an undisturbed soil wall.

Backfill and compact the soil carefully so the three electrodes remain in close contact with the surrounding soil.

For hard soil, prepare an appropriate pilot hole before inserting the sensor. The probe should not be hammered or subjected to strong impact.

Soil EC Sensor for Irrigation and Fertigation

The NBL-S-TMC is particularly suitable for projects where irrigation water status and soluble salt conditions need to be monitored together.

NBL-S-TMC → RS485 → Irrigation Controller / Data Logger → 4G / Ethernet → Cloud or Private Server

The three measurement channels support different aspects of root-zone management:

Suitable EC ranges and management thresholds depend on crop species, growth stage, soil or substrate, irrigation water quality, fertilizer program and measurement method.

Nutrient Solution and Water-Fertilizer Applications

The conductivity channel can also be used for suitable water-fertilizer solutions, nutrient solutions and cultivation substrates within the specified measurement range.

For nutrient-solution applications, confirm that the expected conductivity remains within 0–10000 μS/cm and that the installation, cleaning and measurement conditions are suitable for continuous operation.

Multiple NBL-S-TMC Sensors on One RS485 Network

Multiple sensors can share one RS485 communication bus when each sensor has a unique Modbus device address.

• Assign a unique Modbus address to each sensor.

• Use twisted-pair cable for RS485 A/B communication.

• Prefer daisy-chain wiring where practical.

• Use a suitable DC power supply.

• Calculate voltage drop for long cable runs.

• Use appropriate termination where required.

• Record the sensor address, installation position and measurement depth.

A clear monitoring-point identification format can simplify system maintenance and data analysis:

Field A → Zone 03 → Depth 30 cm → Modbus Address 07

Factors That Affect Soil EC Readings

Applications of the NBL-S-TMC

• Smart irrigation

• Fertigation monitoring

• Greenhouse cultivation

• Soil salinity monitoring

• Precision agriculture

• Vegetable production

• Fruit orchards

• Grassland and pasture monitoring

• Scientific experiments

• Plant cultivation

• Soil research

• Agricultural IoT systems

Integration with Weather Stations and Agricultural IoT

Combining soil EC, moisture and temperature measurements with weather and irrigation data provides a more complete view of root-zone conditions.

Rainfall + Irrigation + Soil Moisture + Soil EC + Soil Temperature → Root-Zone Monitoring

The NBL-S-TMC can connect to the same data-acquisition system as compatible weather sensors, allowing soil and meteorological data to be viewed together on a cloud platform or customer-owned server.

NBL-S-TMC Soil Temperature, Moisture and EC Sensor vs Other Soil Sensors

Common Soil EC Measurement Errors

• Interpreting EC as an individual N, P or K measurement

• Comparing EC readings collected under very different soil-moisture conditions

• Ignoring the salinity of irrigation water

• Measuring immediately beside concentrated fertilizer

• Leaving air gaps around the electrodes

• Using one monitoring point to represent a highly variable field

• Ignoring installation depth

• Using duplicate Modbus addresses on the same RS485 network

• Failing to document measurement location and irrigation conditions

Soil EC Sensor FAQ

Q1. What does the NBL-S-TMC measure?

A1. The NBL-S-TMC simultaneously measures soil temperature, soil moisture and electrical conductivity.

Q2. What is the soil EC measurement range?

A2. The EC measurement range is 0–10000 μS/cm with 1 μS/cm resolution.

Q3. What is the EC accuracy?

A3. The specified EC accuracy is ±5% within the 0–10000 μS/cm measurement range.

Q4. Which technology is used for soil moisture measurement?

A4. The soil moisture channel uses FDR (Frequency Domain Reflectometry) technology.

Q5. Does the NBL-S-TMC measure NPK?

A5. No. It measures electrical conductivity rather than individual nitrogen, phosphorus or potassium concentrations.

Q6. Is soil EC the same as salinity?

A6. EC and salinity are related but are not identical measurements. EC measures electrical conductivity and is commonly used as an indicator of soluble salt conditions.

Q7. Why does soil moisture affect EC?

A7. Dissolved ions conduct electricity through soil water. Very dry soil provides a less continuous conductive pathway, so EC values should be interpreted together with moisture conditions.

Q8. Does the sensor compensate EC for temperature?

A8. Yes. The EC channel includes built-in temperature compensation over a specified 0–50°C range.

Q9. Can the NBL-S-TMC remain buried for long-term monitoring?

A9. Yes. The IP68 probe is suitable for long-term monitoring when installed correctly and good contact with the measured soil or substrate is maintained.

Q10. Can several NBL-S-TMC sensors share one RS485 bus?

A10. Yes. Each sensor requires a unique Modbus address, and the RS485 wiring, power supply and termination should be designed correctly.

Q11. Can the sensor be used for nutrient solutions?

A11. Yes. The EC channel can be used for suitable nutrient solutions and water-fertilizer applications when conductivity remains within the specified 0–10000 μS/cm measurement range.

Q12. Can NBL-S-TMC data be sent to a private server?

A12. Yes. The RS485 sensor can connect to a compatible data logger or IoT gateway, which can transmit measurements through MQTT, HTTP or TCP depending on the system configuration.

NBL-S-TMC Soil Temperature, Moisture and EC Sensor Datasheet

NBL-S-TMC-Soil-temperature-and-moisture-conductivity-sensor.pdf

Request an NBL-S-TMC Quotation

The NBL-S-TMC can be supplied for individual monitoring points or larger multi-sensor agricultural systems. Selection should consider sensor quantity, cable length, installation depth, expected EC range, communication distance and the required data-acquisition system.

For irrigation and fertigation projects, the sensor can be integrated with PLCs, irrigation controllers, RS485 data loggers, LoRaWAN nodes, 4G gateways and private monitoring platforms.

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