Bowenby observation system

energy balance-Bowen ratio method (EBBR) refers to a method of calculating latent and sensible heat fluxes by measuring net radiation, soil heat flux, temperature difference, and water vapor pressure difference. The measurement system mainly consists of four parts: data collector, high-precision sensor, automatic transposition system, and automatic switching system. Among them, the data collector collects and stores net radiation and soil heat flux, etc; The temperature and humidity differences collected and stored by the automatic transposition measurement system, as well as the triggering transposition control of the automatic transposition device;

British physicistBowen (1926) proposed the Energy Balance Bowen Ratio (EBBR) method for studying the energy balance of a free water surface. The method utilizes the ratio of the turbulent heat exchange between the water surface and the air (sensible heat flux H) to the heat consumption of evaporated water vapor on the free water surface (latent heat flux LE), and combines the energy balance formula to obtain the sensible and latent heat fluxes.

The Bowen ratio derivation formula is as follows:

among which,β is the Bowen ratio, and Kh and Kq are the turbulent exchange coefficients of water and heat, respectively (assuming Kh Kq);For the wet bulb constant,0.665（kPa/℃）； L is the coefficient of latent heat of evaporation, 2.45 (MJ/kg); Cp is the specific gas constant;Temperature difference (measured temperature difference can be used)Substitute); The water vapor pressure difference between two different observation layers.

By using transposition technology, the systematic errors generated by the measuring instrument itself can be eliminated, thereby significantly improving the measurement and calculation accuracy of the Bowen ratio. Take the average of the difference between two sets of measurement values of two temperature and humidity sensors in one rotation cycle to eliminate system errors and improve the measurement accuracy of the Bowen ratio.

System Composition

1) CR3000 Data Collector

*Large scanning rate:100Hz

Analog input channel:28 single ended or 14 differential pairs

Pulse counter:4 of them

Switching laser channel:4 voltage excitations, 3 current excitations

Digital control port:3 SDMs, 8 I/O or 4 RS-232

communication/Data storage ports: 1 CS I/O, 1 RS-232, 1 parallel peripheral device

Input voltage range:±5Vdc

Accuracy of analog voltage measurement:± (0.04% reading+offset), 0～40℃

Simulated resolution:0.33μV

simulation/Number of digits converted: 16 digits

Operating temperature:-25-50 ℃ (standard); -40-85 ℃ (low-temperature expansion)

Memory2MB for running the system, 4MB for CPU, program, and data storage

Power supply requirements:10～16VDC

power waste:2mA (sleep state), 3mA (1Hz sampling frequency), 10mA (100Hz sampling frequency)

Supported communication protocols:PakBus,Modbus, DNP3,SDI-12,SDM

Supported Internet protocols:FTP, HTTP, XML POP3, SMTP, Telnet, NTCIP, NTP

2) HC2A-S3 air temperature and humidity sensor

HC2A-S3 is a temperature and humidity integrated probe produced by Rotronic, Switzerland. It is a highly accurate, sturdy, and durable temperature and humidity sensor suitable for long-term field observation. The sensor is equipped with a polyethylene filter to prevent dust and particles from entering, ensuring the accuracy and reliability of the sensor measurement. After being equipped with polytetrafluoroethylene (PTFE) filters, although HC2A-S3 has a slight decrease in response time (≤ 30s), it can significantly improve environmental adaptability and can be used normally in high salt and high humidity environments such as the ocean.
Main technical parameters

Temperature range:-40-60 ℃ (factory calibrated range); -50 ℃~100 ℃ (temperature limit range)

Temperature accuracy:±0.1℃（@10～30℃）

Relative humidity range:0～99%RH
Relative humidity accuracy:±0.8%RH（@10～30℃）
Long term stability:<1% RH/year
supply Electricity:3.3～5Vdc

3) NR01 Four Component Net Radiation Sensor

Measurement parameters: Upward longwave radiation, downward longwave radiation, total solar radiation, reflected solar radiation, net radiation

Optional measurements: albedo or solar reflectance, sky temperature, sunshine hours, and surface temperature

Shortwave radiation sensor(SW)：

Short wave spectral range:285～3000nm

Calibration traceability to:WRR

Calibration uncertainty: ＜1.8%

Long wave radiation sensor(LW)：

Spectral range:4500～40000 nm

Calibration traceability to:WISG

Calibration uncertainty: ＜7%

Temperature sensor type:Pt100 (temperature of the instrument itself)

Heater power:1.5W @ 12VDC

Operating temperature:-40～80℃

4) Soil heat flux plate

HFP01 is a popular soil heat flux measurement sensor worldwide, which can also be measured through walls and building envelope structures. The sensor adopts a ceramic/plastic composite material body to maintain a small total thermal resistance. The sensor is very sturdy and has stable performance. It is suitable for long-term measurement in one location and system integration measurement in multiple locations.

Technical performance parameters

Measurement parameter: heat flux

Sensing area:8×10^-4m²

quantity Cheng: -2000～﹢2000W/m²

sensitivity: 60×10^-6V/(W/m²)

Sensor thermal resistance:71×10^-4K/(W/m²)

Sensor resistance range1-4Ω

Calibration uncertainty:±3%（k=2）

Working temperature range:-30～70℃

IP protection level: IP67

5) 03002 Wind Speed and Direction Sensor

Operating temperature:-50～50℃

Wind speed measurement

Measurement range:0～50m/s， Gust of 60m/s
Accuracy:±0.5m/s

Start wind speed:1.1m/s

Output signal: AC sine wave, per revolution1 pulse

Wind direction measurement

range0-360 ° (mechanical), 0-352 ° (electronic, 8 ° opening)
Accuracy:±5°

Start wind speed:1.3m/s

Output signal: Analog voltage signal

supply Electricity: Potentiometer excitation voltage * large15VDC（03002）

6）TCAVAverage soil temperature sensor

The TCAV soil average temperature probe adopts an E-type (nickel chromium constantan) thermocouple probe, which is used to measure the average temperature of soil below the surface layer by 6-8 cm. It can measure the average temperature of small areas of soil in both vertical and horizontal directions. Each set of probes has 4 parallel probes, each measuring temperature at different depths. TCAV can be used in conjunction with soil heat flux plates and soil temperature and humidity sensors to calculate the total soil heat flux.

Technical performance parameters

Sensor type: Nickel cadmium-Copper thermocouple
Typical output:60μV/℃

Weight:0.45kg (including 15.24m cable)