Campbell Scientific BlackGlobe-L Black Globe Temperature Sensor

Overview

The Campbell Scientific BlackGlobe-L is a precision-engineered black globe thermometer designed for accurate, field-deployable measurement of globe temperature—a critical input parameter in the calculation of Wet Bulb Globe Temperature (WBGT). WBGT is an internationally recognized thermal stress index defined by ISO 7243 and adopted by ACGIH, OSHA, and NIOSH for occupational heat stress assessment. Unlike ambient air temperature sensors, the BlackGlobe-L replicates human thermal absorption characteristics through its standardized 15.2 cm (6-inch) diameter hollow copper sphere, coated with matte-black paint (emissivity ≥ 0.95) to maximize radiative heat exchange. Internal thermistor placement ensures minimal thermal lag and high spatial representativeness of mean radiant temperature (MRT), enabling robust estimation of combined convective, conductive, and radiative heat loads on the human body.

Key Features

• Calibrated 15.2 cm (6″) hollow copper sphere with high-emissivity matte-black coating (ε ≥ 0.95) conforming to ISO 7243 and ASTM D6828 specifications for globe geometry and surface properties
• Integrated precision thermistor with traceable NIST-calibrated response curve, optimized for stability across wide thermal gradients
• Interchangeability error ≤ ±0.2 °C over the core operational range (0–70 °C), supporting multi-sensor deployments without individual recalibration
• Ruggedized stainless-steel mounting bracket and UV-resistant cable jacket rated for continuous outdoor exposure from -50 °C to +100 °C
• Low-power analog voltage output (0–2.5 V) compatible with Campbell Scientific’s full datalogger ecosystem—excluding CR200X series—enabling seamless integration into existing environmental monitoring networks
• Maximum cable length of 305 m (1000 ft) supported without signal degradation, facilitating flexible sensor placement in large-scale industrial or athletic venues

Sample Compatibility & Compliance

The BlackGlobe-L is not used in isolation but as a primary component in WBGT measurement systems that comply with ISO 7243:2017 (Ergonomics of the thermal environment — Estimation of the heat stress on working individuals, based on the WBGT index) and ACGIH TLV® guidelines. It requires co-deployment with a natural wet-bulb thermometer (e.g., CS215 or HYDRO-TECH WBT) and a dry-bulb thermometer (e.g., 107 or HMP155) to compute the full WBGT equation: WBGT = 0.7×T_nwb + 0.2×T_g + 0.1×T_db (outdoors) or WBGT = 0.7×T_nwb + 0.3×T_g (indoors). Its physical design meets ANSI/ASHRAE Standard 55-2023 requirements for globe sensor dimensional fidelity and thermal mass equivalence. The device carries no CE or UKCA marking but is supplied with full calibration documentation traceable to NIST standards, suitable for GLP-compliant occupational health reporting and internal audit readiness.

Software & Data Management

Data acquisition is performed via Campbell Scientific’s LoggerNet, PC400, or RTDAQ software platforms, which support automated WBGT index derivation using user-defined equations or preconfigured calculation scripts. Raw thermistor resistance values are converted to temperature using a fifth-order polynomial calibration equation stored in the datalogger’s program memory. All measurements—including timestamp, sensor ID, and diagnostic flags—are logged with microsecond-level time synchronization when paired with GPS-enabled dataloggers (e.g., CR6 or CR1000X). Audit trails, data integrity checks, and export to CSV/NetCDF formats ensure compatibility with enterprise EHS management systems (e.g., Intelex, Sphera) and regulatory reporting workflows compliant with OSHA 1910.136 and EU Directive 89/654/EEC.

Applications

• Ongoing real-time heat stress monitoring in construction sites, mining operations, foundries, and power generation facilities
• Validation of HVAC performance and thermal comfort compliance in indoor manufacturing environments per ISO 7730
• Field validation of predictive thermal models used in military training, wildfire suppression, and emergency response planning
• Research-grade studies on physiological strain indices in sports science, including NCAA and IOC heat acclimatization protocols
• Long-term climate resilience assessments for infrastructure projects requiring occupational exposure modeling under projected warming scenarios

FAQ

What is the difference between globe temperature and ambient air temperature?
Globe temperature reflects mean radiant temperature (MRT), integrating solar radiation, surface re-radiation, and convective exchange—whereas ambient air temperature measures only convective heat transfer. MRT often exceeds air temperature by 5–20 °C in direct sunlight, making globe temperature essential for accurate WBGT computation.
Can the BlackGlobe-L be used indoors without solar exposure?
Yes. It remains valid for indoor WBGT assessment where radiant heat sources include hot machinery, furnaces, or heated ceilings—conditions where MRT deviates significantly from dry-bulb temperature.
Is recalibration required after field deployment?
While the thermistor exhibits long-term stability, Campbell Scientific recommends annual NIST-traceable recalibration for applications subject to regulatory audit or GLP/GMP compliance requirements.
Why is the CR200X series excluded from compatibility?
The CR200X lacks sufficient excitation voltage resolution and analog input precision to meet the ±0.2 °C interchangeability specification; newer dataloggers (CR6, CR1000X, CR300) provide programmable excitation and 24-bit ADC resolution necessary for metrological consistency.
Does the sensor require ventilation or aspiration?
No. The BlackGlobe-L operates passively per ISO 7243 specifications; forced-air aspiration would distort radiant heat exchange and invalidate WBGT compliance. Natural convection is integral to its standardized thermal response profile.