ST640 Series
Low-cost general-purpose handheld infrared thermometer


  • Low-cost, temperature gun-style infrared thermometer
  • Temperature range: -35°C to 550°C
  • Laser sighting with on/off switch
  • Fixed emissivity 0.95, ideal for use on rubber, wood, asphalt, plastics, painted surfaces, organic materials and many more
  • Backlit display
  • Audible alarms
  • Not designed or approved for fever detection


  • All the features of the ST640, plus:
  • Adjustable emissivity setting for accurate readings on a variety of surfaces
  • Type K thermocouple input
  • Automatic emissivity adjustment using the thermocouple measurement
  • Not designed or approved for fever detection
ST640 ST642
Emissivity Setting Fixed at 0.95 Adjustable 0.1 to 1.0
Type K Thermocouple Input NO YES
eSmart Emissivity Correction NO YES
Audible Alarm YES YES
CIS Visual Alarm YES YES
°C/°F Switchable YES YES
Display Backlight YES YES
Laser Sight, Switchable YES YES
Max, Min, Avg, ΔT YES YES
Carrying Case Included YES YES

General Specifications

Field of View
Temperature Range
-32°C to 535°C (-25°F to 999°F)
±3°C (±5°F) from -32°C to -20°C (-25°F to -4°F)
±2°C (±3°F) from -20°C to 100°C (-4°F to 212°F)
±2% above 100°C (212°F)
Spectral Range
5 to 14 μm
±1°C (±2°F)
0.1°C (0.1°F)
Response Time
500 ms
Operating Temperature
0°C to 50°C (32°F to 122°F), 10% to 90% RH
Power Off
Automatic after approximately 7 seconds
LCD with backlighting
Battery Type
9 V, PP3 (not supplied)
180 x 130 x 40 mm
195 g
Please note: The given measured spot size contains 90% of the energy detected by the sensor. We normally recommend the target is at least twice as large as the given measured spot for maximum accuracy. The thermometer may be used at longer distances than the above diagram shows, with a proportionally larger measured spot.
Model Description Price
ST640 Handheld infrared thermometer with fixed emissivity setting Contact Calex
ST642 Handheld infrared thermometer with adjustable emissivity setting and Type K thermocouple input Contact Calex