Soil water potential meter

Technical parameter

Working power supply DC 8V~14V (wired version model TP-SZL) DC 6V (wireless version model TPSAR-SZL)

Working current<30mA (wired version)<50mA (wireless version)

Standby current<1mA (wired version)<10mA (wireless version)

Environmental temperature 0-70 ℃

Measurement range -100kPa to 0

Measurement accuracy of 0.25kPa, 0.5% FS

Response time ≤ 30s

Wired interface RS-485, using TOP standard serial port data protocol

operational principle

Sensors are suitable for measuring soil moisture at any point in the soil. When the soil dries, the surface tension potential of the humidity in contact with the ceramic head tends to suck out the water inside the pipe. Thus, a local vacuum is formed at the top of the tube. After irrigation or rainfall, water is sucked back into the pipe, reducing the vacuum degree. A high vacuum reading indicates dry soil, while a low reading indicates moist soil. A reliable instrument for irrigation management. Suitable for all agricultural research and production: grasslands, pastures, crops, orchards, vineyards, etc.

Usually, a certain number of monitoring points should be arranged in irrigation areas. Each point should have 2-3 sensors of different lengths. This not only allows us to understand the water content at different depths of each point, but also the movement of water during irrigation.

By using a timed collection device, summarize the data, such as 2-3 times a week, and then draw a soil moisture movement map. The test results should be combined with the water requirements of different crops learned from the agricultural department, so that irrigators can estimate the water requirements for the next irrigation cycle and be prepared a few days before the irrigation day. Each component is detachable and easy to replace and maintain. The length of the pipe is 15-90cm (measured depth), which can meet most usage requirements. Special lengths can be processed according to user requirements.

Key points for installation and use

1. Soak the water potential probe (ceramic head) in water for at least 3 hours before use;

2. Inject cooled boiled water from the top of the plastic pipe (the raw water contains a large amount of bubbles); Seal each component of the water potential in place. Pay attention to placing the “O” – shaped sealing ring in place before installing each component;

3. Use a soil drill to drill holes at the selected burial point to the predetermined depth. Pour about 5mL of mud into the bottom of the hole and insert the water potential probe into the hole. Compact the soil around the plastic pipe.

4. The burial depth of the water potential probe is calculated from the distance from the middle of the ceramic pipe to the soil surface. The water potential probe is buried in moist soil for 1 hour, and after drying the soil for a few hours, it can be measured. A stable reading takes several hours;

5. When the water level inside the pipe drops significantly, it is necessary to replenish the cooling water;

If the water level drops too quickly, it indicates that the seal is not properly sealed and needs to be checked or reinstalled.

7. Calculation: As shown in the following figure (image for reference * subject to actual object):

Soil water potential (KPa)=water potential reading – probe water column height (cm)/10.2.

In the formula, 10.2 refers to the conversion coefficient from centimeter water column height to kilopascals (KPa).

Probe water column height: refers to the height from the scale line to the center of the ceramic head.

Soil water potential measurement value and soil condition reference:

a. The measurement force value is within the range of -10 to 0Kpa: indicating humidity, which is too high for most crops.

b. The measurement force value is within the range of -30 to -10Kpa: indicating humidity, suitable for the growth of most crops.

c. The measurement force value is within the range of -50 to -30Kpa: indicating that dry and wet crops require watering.

d. Measurement force value within the range of<-50Kpa: indicates dryness, and most crops require irrigation.