Fine-wire thermocouple in aspirated radiation shield
Overview
The ASPTC-L consists of a type-E fine-wire thermocouple mounted in a fan-aspirated radiation shield to provide highly accurate air temperature measurements. One ASPTC can measure absolute air temperature, or two ASPTCs can make delta temperature measurements. Often, the ASPTC replaces, or is measured in addition to, the TCBR thermocouples in a Bowen ratio system.
Read MoreBenefits and Features
- Uses fine-wire thermocouple for accurate air temperature measurements
- Includes aspirated radiation shield
- High-powered fan reduces solar loading
Images
Detailed Description
The ASPTC's radiation shield is an elongated tube constructed from white UV-stabilized polyethylene that provides low thermal conductivity and heat retention. A fan draws air across the measurement junction, which reduces solar loading on the thermocouple. The radiation shield also protects the thermocouple, increasing the thermocouple’s durability.
The ASPTC's fine-wire thermocouple consists of a chromel wire and a constantan wire joined at a measurement junction. A voltage potential is generated when the measurement end of the thermocouple is at a different temperature than the reference end of the thermocouple. The magnitude of the voltage potential is related to the temperature difference. Therefore, temperature can be determined by measuring the differences in potential created at the junction of the two wires.
A reference temperature measurement is required for thermocouple measurements. The temperature sensor built into many of our dataloggers' wiring panel typically provides this measurement.
Specifications
| Shield Material | UV-stabilized polyethylene |
| Large Diameter | 5.8 cm (2.3 in.) |
| Small Diameter | 4.6 cm (1.8 in.) |
| Power Cable Diameter | 0.5 cm (0.2 in.) |
| Signal Cable Diameter | 0.3 cm (0.1 in.) |
| Length | 53.3 cm (21 in.) |
| Height | 14.7 cm (5.8 in.) |
| Weight | 0.86 kg (1.9 lb) |
Fan |
|
| Air Velocity at Thermocouple | 5.5 m/s (@ 12 Vdc) |
| Life Expectancy | 65,000 h (@ 30°C) |
| Current Drain | 260 mA (@ 12 Vdc) |
| Operating Voltage | 9 to 13 Vdc |
| Operating Temperature Range | -10° to +70°C |
| Polarity Protection | Reverse polarity protected |
Thermocouple |
|
| Type | Chromel-Constantan |
| Typical Output | 60 μV/°C |
| Accuracy | Refer to the Thermocouple Measurement section in the data logger manual. |
| Diameter | 0.0762 mm (0.003 in.) |
Compatibility
Please note: The following shows notable compatibility information. It is not a comprehensive list of all compatible products.
Dataloggers
| Product | Compatible | Note |
|---|---|---|
| CR1000 (retired) | ||
| CR1000X | ||
| CR3000 (retired) | ||
| CR6 | The CR6 is compatible when used with the CDM-A108 or CDM-A116. | |
| CR800 (retired) | ||
| CR850 (retired) |
Additional Compatibility Information
Mounting
The ASPTC can be mounted to a tripod or tower via the UT018-5 crossarm or a user-supplied crossarm that has a square cross-section of 3.8 cm by 3.8 cm (1.5 in. by 1.5 in.). For circular cross-section crossarms, a mounting bracket kit designed for circular crossarms comes with the ASPTC and can replace the square bracket.
Power Considerations
The ASPTC is typically powered with a user-supplied deep-cycle battery that is recharged with an SP20R, SP50, or SP90 solar panel; for high current drain systems, two SP90 solar panels may be used to provide 180 W of power. The data logger’s rechargeable battery can only be used if it is connected to ac power. For help analyzing your system’s power requirements, refer to our Power Supply brochure or application note.