Kestrel 5400 as your WBGT meter: how it compares with MOM's requirements
A pocket-sized alternative to the traditional tripod WBGT meter. How the Kestrel 5400's specs line up with MOM's guidelines, and how to use it properly.
Sites that must measure WBGT on site (construction projects of S$5 million or more, shipyards and the process industry) need a meter that meets MOM's specification. The traditional choice is a tripod-mounted unit with a wet wick and a large black globe. A popular alternative is the Kestrel 5400 Heat Stress Tracker, a rugged handheld meter.
Here is how it compares with what MOM asks for, and what to watch out for.
How the Kestrel 5400 measures WBGT
A traditional WBGT meter uses three sensors: a wetted wick (natural wet bulb), a 150 mm black globe and an air thermometer. The Kestrel 5400 works differently:
- No wet wick. It calculates the natural wet bulb temperature from its digital sensors for temperature, humidity, wind and pressure. There is no water reservoir to fill or wick to replace.
- A small 25 mm globe. The manufacturer converts its reading to the equivalent of a standard 150 mm globe.
- Built-in logging. It stores more than 10,000 readings and can send them to a phone or computer over Bluetooth with the LiNK option.
Specs against MOM's guidelines
| Item | MOM guideline | Kestrel 5400 (manufacturer's spec) |
|---|---|---|
| WBGT accuracy | ±2°C | ±0.7°C |
| Resolution | 0.1°C | 0.1°C |
| Globe temperature range | 10 – 60°C | −29 – 60°C |
| Air temperature range | 10 – 50°C | −29 – 70°C |
| Stabilisation before reading | At least 10 minutes | About 8 minutes to 95% accuracy, about 15 minutes to 99% |
| Calibration | Yearly, by an authorised supplier or SAC-accredited lab | Check that your supplier or lab can calibrate it |
On paper, the Kestrel 5400 meets or exceeds MOM's accuracy and resolution requirements. MOM's guidelines set out performance and calibration requirements rather than naming brands, so keep the specification sheet and calibration certificate on file to show the meter meets them.
Tips for accurate readings
- Give it 15 minutes. MOM asks for at least 10, but the Kestrel reaches its best accuracy at about 15 minutes after being moved.
- Mount it about 1 metre above the ground, in direct sun, where people work. A tripod or vane mount keeps it steady and lets it face the wind.
- Do not hold it in your hand while measuring; body heat and shade affect the reading.
- Set alert thresholds at 31, 32 and 33°C so the meter flags each MOM band.
- Download the log regularly and keep it with your site records.
- Calibrate every year. MOM publishes a list of accredited calibration laboratories.
Pros and cons
Why sites choose it
- Compact, waterproof and drop-tested, so it survives a construction site
- No wick to keep wet, so readings do not drift when someone forgets to top up
- Logs data automatically, which makes the hourly record easier
What to keep in mind
- It still needs a person or a mount in the right spot; it is not a fixed real-time station
- The wet bulb is calculated rather than measured with a wick, so treat the manufacturer's validation and your calibration certificate as your evidence
How HeatAware helps
HeatAware kits for sites that need on-site measurement include a Kestrel 5400 WBGT Heat Stress Tracker, set up with alerts for MOM's bands. The first year is covered, and the yearly renewal includes calibration by a SAC-accredited lab. The app records readings and alerts so your hourly log is always ready.
Size your kit to see whether your site needs an on-site meter. For the full measurement procedure, read MOM's WBGT monitoring guidelines, explained.
Specifications from the manufacturer's Kestrel 5400 data sheet; requirements from MOM's Guidelines on WBGT Monitoring for Outdoor Work and its FAQs. MOM's guidelines do not name specific brands. Check the latest specifications with your supplier.