Sentry ST640 Thermal Imager 12:1 DS -32~535°C 640/642

Thermal imager range and ratio

The Sentry ST640 is a thermal imager built for electricians and technicians who need non-contact temperature readings. It offers a distance-to-spot ratio of 12:1 and measures from -32 °C to 535 °C on the 640 and 642 models. Automatic emissivity measurement removes the need for manual surface adjustments. Rugged ergonomics support daily use on site.

Suited for electrical and HVAC checks

This tool suits professionals scanning panels, motors or ductwork where quick spot measurements are required. The colour-alert system flags temperatures that exceed a user-set threshold. Buyers who need a higher range up to 760 °C should consider the 643 variant instead. It is not intended for users who require imaging resolution specifications not provided here.

Distance-to-spot 12:1 decides fit

The 12:1 distance-to-spot ratio determines how close you must be for an accurate spot size. At twelve units of distance the measured spot is one unit wide. If your inspection points are farther away than this ratio allows, the reading will average a larger area and lose detail. Verify the working distance before purchase.