STP01
Soil temperature profile sensor with self-test
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- measures at five depths
- thin design leaves soil structure intact
- on-line self-test
Soil temperature profile sensor with self-test
STP01 accurately measures the temperature profile of the soil at 5 depths close to its surface. It is used for scientific-grade surface energy balance measurements. The sensor is buried and usually cannot be taken to the laboratory for calibration. The on-line self-test using the incorporated heating wire offers a solution to verify STP01’s measurement stability.
- measures at five depths
- thin design leaves soil structure intact
- on-line self-test
Specifications
| measurement range | -30 to +70 °C |
| on-line functionality testing | self-test using the incorporated heater |
| measurand | temperature at 5 depths from 0 to 0.5 m |
| temperature sensors | matched thermocouples type T |
| uncertainty of temperature difference measurement | 1.5 % of measured value plus measurement system uncertainty in x 10⁻⁶ V/40 |
| uncertainty of relative position | ± 0.001 m |
| rated operating environment | surrounded by soil |
| reference temperature sensor | Pt100, IEC 751:1983 class B |
All specifications
| measurand | temperature at 5 depths from 0 to 0.5 m |
| measurement range | -30 to +70 °C |
| temperature sensors | matched thermocouples type T |
| uncertainty of temperature difference measurement | 1.5 % of measured value plus measurement system uncertainty in x 10⁻⁶ V/40 |
| uncertainty of relative position | ± 0.001 m |
| rated operating environment | surrounded by soil |
| on-line functionality testing | self-test using the incorporated heater |
| reference temperature sensor | Pt100, IEC 751:1983 class B |
| sensor foil thickness | 0.6 x 10⁻³ m, 2.5 x 10⁻³ m at Pt100 |
| standard cable length (2 cables) | 5 m (see options) |
| IP protection class | IP67 |
| optional non-traceable measurand | thermal conductivity at 3 depths |
| heater rated power supply | 9 to 15 VDC |
| power consumption daily average | 0.005 W |
| interval between self-tests | 24 h |
| self-test duration | 600 s |
| order code | STP01/cable length in m |
| * measurement depths | |
| – 0.02 m | |
| – 0.05 m | |
| – 0.1 m | |
| – 0.2 m | |
| – 0.5 m | |
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Improved accuracy & quality assurance
STP01 soil temperature profile sensor offers an accurate temperature difference measurement at five measurement locations at 0.02, 0.05, 0.1, 0.2, and 0.5 m below the soil surface. It also has a well-specified and fixed distance between the measurement locations. STP01 contains 5 matched thermocouples, at locations A to E in Figure 5, and one reference temperature sensor (Pt100 type) at location E at 0.5 m depth. By having the reference temperature measurement in the sensor and only measuring differential thermocouple voltages (relative to the reference at 0.5 m), the uncertainty of the temperature difference measurement is very low: ± 0.02 °C is attainable. Simple copper-conductor signal wire is used in STP01’s cable.
As an extra, a heating wire is incorporated in STP01. Analysis of the temperature change during the heating interval serves as a self-test. Soil temperature sensors are preferably left in the soil for as long as possible, so that the soil properties become representative of natural conditions. Using self-testing, the user no longer needs to take sensors to the laboratory to verify their stable performance. The result is a much improved accuracy & quality assurance of the measurement relative to measurements with conventional sensor types.
STP01 advantages
- high accuracy, scientific measurement of soil energy balance, with a high level of data quality assurance
- high accuracy K/m temperature gradient measurement by accurate positioning of the thermocouple joints (± 0.001 m), and accurate temperature difference measurement (± 0.05 K)
- high accuracy and stability of the relative distance between sensors (± 0.0005 m)
- thin, 0.6 x 10-3 m thickness, construction that leaves the soil structure intact
- simple copper-core signal wire; no special connectors needed
Suggested use
high accuracy, scientific-grade measurement of the soil energy balance, with a high level of data quality assurance.
Areas of application
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