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TWL-1S is designed to measure WBGT and thermal work limit (TWL) heat index. The TWL measures air temperature, humidity, radiant heat and wind speed to come up with instructions for work, rest and hydration plan. We integrate the algorithm of TWL and work-rest schedule based on the latest guideline. The user-friendly interface even showed different colors to ensure users in line with TWL schedule. For example, red means unsafe for work, yellow means buffer zone and green means safe for work.


Smart User-Friendly Interface

Meters were supposed to sense the targets and give readings. Scarlet intends to do more. TWL theory determines the threshold for safe, fair, and dangerous working environment. Colorful LCD backlight tells you the risk level based on the TWL value. Work-rest schedule and fluid intake are integrated into the display. A countdown timer shows the time remaining before a recommended rest.



  • Wet Bulb Globe Temperature (WBGT)
  • Thermal Work Limit (TWL)
  • Globe Temperature
  • Dry Bulb Temperature
  • Relative Humidity
  • Wet Bulb Temperature
  • Wind Speed

Smart Heat Stress Meter TWL-1S 熱指數黑球溫度計

  • Item Description
    Air Temperature Range 0…60 °C / Accuracy ±0.6 °C
    Globe Bulb Indoor Range 0...80 °C / Accuracy ±1.0 °C (15...40 °C); ±1.5 °C (others)
    Globe Bulb Outdoor Range 0...80 °C / Accuracy ±1.5 °C (15...40 °C); ±2.0 °C (others)
    Relative Humidity Range 5...95 %rh / Accuracy ±3% (at 25 °C; 10...90 %rh) ±5% (others)
    Wind Speed Range 0.5...10 m/s / Accuracy ±(2% of reading + 0.2) m/s
    Dimensions Body 59 x 37 x 316 mm (w x d x h). Wind cup (top view) diameter 182 mm
    Operating range electronics -10…60 °C
    Accuracy at 23 ±5 °C ±1.0 %rh / ±0.2 K
    Power supply / consumption 4 AAA 3V battery, power supply 6 mA consumption without lighting
    Probe protection Polypropylene plastic cage
    Measurement interval 2 seconds
    Data logger Yes. Min data rate 1 min up to 60 min, 2,000 data.
    Connection Interface Mini USB (UART)
    Calibration / adjustment Scarlet calibration kit
    Wireless Connection (Optional) 433 MHz (TWL-1SR Model)
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