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Red handheld infrared thermometer with digital display

Sentry

Sentry ST689 Infrared Thermometer 50:1 DS Ratio -50 to 1000°C

SKU CH-MNAX-9WHB8 MPN ST689

Measures temperature from -50 to 1,000°C at a distance with 50:1 optics and 0.1° resolution

  • Labor warranty1 Year
  • Color and finishRed
  • Number of items1 pack
  • Sold asBox
  • Parts warranty3 Years
  • Non-contact measurement keeps operators at a safe distance
  • 50:1 distance-to-spot ratio enables accurate long-range readings
  • Wide -50 to 1000°C range covers diverse industrial tasks
  • 1°C resolution detects fine temperature variations
  • Rugged compact design suits demanding field use

Non-Contact Infrared Thermometer 50:1 DS Ratio

The Sentry ST689 is a non-contact infrared thermometer built for high-performance temperature measurement. It offers a 50:1 distance-to-spot ratio for accurate long-distance readings across a range of -50 to 1000°C. The rugged, compact design suits electricians and technicians needing reliable data in demanding environments.

Suits long-range industrial checks.

This tool suits professionals measuring equipment, electrical panels, or HVAC systems from a safe distance where a 50:1 spot size is required. It is not for applications exceeding 1000°C such as certain foundry or advanced metalworking tasks needing a wider range. Buyers needing contact probes or data logging features should consider other instruments.

50:1 distance-to-spot ratio decides fit

The 50:1 distance-to-spot ratio is the critical specification determining if this model matches the job. It allows measuring a small target area from fifty times the distance, essential for inaccessible or hazardous locations. If the working distance requires a tighter 30:1 ratio or a broader field of view, a different series model would be appropriate.

How it compares

Measured against everything we stock in Electrical Trade Tools & Kits, at today’s prices. Recalculated every night.

Price $410.99
Pricier than about 90% of the 5,006 comparable items (median $95.99).

Specifications

Product
Brand nameSENTRY
Model nameST689
Color and finishRed
In the box
Number of items1 pack

Questions about this item

How do I set the 50:1 distance-to-spot ratio on the ST689 before taking a reading?

Aim the sensor at the target so the measured spot matches the 50:1 ratio; the laser pointer marks the centre while the optics define the exact spot size at that distance.

What maintenance does the ST689 need over time?

Keep the lens clean with a soft cloth and replace the battery when the low-power indicator appears; the unit carries a three-year parts and one-year labour guarantee.

At what temperature does the ST689 stop measuring?

The upper limit is 1000 °C (1832 °F); readings above this are outside the specified range.

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