Description
The Elcometer 309 Delta T Hygrometer lets coating crews check surface conditions in seconds before paint goes onto steel. Take a reading of Delta T and relative humidity on site and know straight away whether it is safe to start spraying.
Where the Elcometer 309 is used
On tank, pipeline and structural steel jobs, coating inspectors rely on the 309 for a clear go/no-go before spraying begins. In hot coastal conditions and on night shifts, a quick Delta T and RH check helps prevent dewpoint and humidity from trapping moisture under the coating film.
Why Delta T and RH matter
Paint data sheets nearly always set two climate limits: Delta T (surface temperature minus dewpoint) and relative humidity. If Delta T falls below about 3°C (5°F), moisture can settle on the steel and the coating may fail. Maximum RH limits are typically 75–85%. The 309 reads both values quickly and shows a pass/fail result right at the work area.
Key features
- Delta T preset above the industry 3°C threshold, with an on-screen tick/cross and red/green LEDs
- RH 0–100% (±3%), with a user-adjustable upper limit (default 75%)
- Surface/air temperature range of −20°C to +80°C, with 0.1 (°C/°F) and 0.1% RH resolution
- Hold/release function to freeze a reading for your log sheet
- Backlight for tanks, scaffolding and night work
- Waterproof / dustproof body with sealed sensors
- Powered by 2 AA batteries or USB, with 40+ hours of battery life (backlight off)
- Follows common dewpoint practice under ISO 8502-4 and BS 7079-B4
What’s in the box
- Elcometer 309 Delta T Hygrometer
- Wrist strap
- 2 × AA batteries
- Protective carry pouch with belt clip
- RH probe calibration certificate
- Operating instructions
Part number: G309—-1
Elcometer 309 vs 319
Choose the 309 for fast spot checks and a clear pass/fail on Delta T and RH. Step up to the Elcometer 319 when you need full climate logging, statistics and Bluetooth/USB records for inspection and test plans (ITPs) and client documentation.
