5.2.1. Infrared spot thermometers
Infrared spot thermometers may be used for surface temperature measurement of larger targets, such as combs, hive walls, soil, etc. The size of the measurement spot increases with distance to the measured object. In most instruments, spot size is too large for body temperature measurements in honey bees. Some devices offer a close-up lens for spot size reduction. Spot size, however, has to be considerably lower than the honey bee thorax diameter of ~4 mm, because accurate measurements in spherical objects are only possible at an angle smaller than ~30° from the normal to the surface. Care has to be taken that a built-in laser indicator for measurement spot identification really hits the target in close vicinity to the measured object. Parallax errors may lead to false measurements. Nowadays, however, handheld thermographic cameras (see section 18.104.22.168.) have become so cheap that there is no need of using such devices for honey bee body temperature measurement. In fact, they are mostly useless for this purpose.