TWL-1S Heat Stress Monitor

Designed to Prevent Heat Stroke and Illness for Workers in High Temperature Environments.

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  • Overview
  • Features
  • Specifications
  • Applications
  • Support
  • Video

Scarlet TWL-1S is designed to prevent heat stroke and illness for workers. Risk assessment for heat-related illness in the worksite is quite essential in high temperature environments. TWL-1S can be applied at outdoor and indoor working environments. The TWL-1S can measure Wet Bulb Globe Temperature (WBGT), Thermal Work Limit (TWL), Globe Temperature, Dry Bulb Temperature, Relative Humidity, Wet Bulb Temperature and Wind Speed. The 433 mHz wireless paging technology can actively warn HSE officers at the distance of 200 metres.

The cup anemometer captures winds from any direction. You do not have to manually decide the wind direction before measuring the wind speed. Compared to the impeller, wind cup is not restricted to the direction of the wind. It considers all the horizontal components of winds that move the anemometer. A silicone pad covers the top of the bearing to prevent it from dust accumulation.

Additionally, the TWL-1S can record data with configurable sampling rate. PC side software helps download the data for further analysis using other analytical tools, and it also synchronises the date and time of the device with PC.

  • Designed to monitor heat stress
  • 2 Heat Indices: TWL and WBGT
  • Measurement:
    • Wet Bulb Globe Temperature (WBGT)
    • Thermal Work Limit (TWL)
    • Globe Temperature
    • Dry Bulb Temperature
    • Relative Humidity
    • Wet Bulb Temperature
    • Wind Speed
  • Datalogging
  • Risk Level Indicator
  • Mini USB Interface
  • Intuitive user interface
  • Wireless remote notification
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
Calibration / Adjustment Scarlet calibration kit
Measurement Interval 2 seconds
Backlight with Backlight
Alarm Indicators Yes
Battery Indicator Low Batt. Display
Battery Life 120 hours with alkaline batteries
Software Scarlet TWLIT
Risk Level Indicator Yes. 3 colour LCD backlight: red (risk), yellow (med), green (safe)
Data Logger Yes. Min data rate 10 min, 2,000 data.
Connection Interface Mini USB (UART)
Enclosure Material ABS
Standard CE compliant


  • Open cut mining
  • Aluminium, metal, cable
  • Glass
  • Construction
  • Workplace health and safety
  • Transportation sites
  • Manufacturing facilities