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Temperature
The 765 is fitted with a solid state temperature sensor that should not normally require
calibration. This sensor is part of the RH sensor and so can be replaced in the same
way as above.
UV & Visible Light
The 765 calibration should not drift with time but to be sure of accuracy the
instrument can be returned to the manufacturer for a calibration check every 2-5 years.
The 765 has a very carefully defined frequency response (i.e. which wavelengths of
light it is sensitive to). Other light meters are often more sensitive to infra red light
than they should be and so will give a higher reading with light sources that contain
infrared (e.g. ordinary filament light bulbs).
Because the 765 has a cosine angular response it may give different readings to the
now obsolete 762 which is relatively directional. In other words the 765 is more
sensitive to light coming at an oblique angle than the 762.
Note that the human eye has a logarithmic response, this means that if two light
meters are placed side by side they may give different readings even if it looks like
they are getting a similar amount of light. To compare the readings on 2 meters they
each need to be placed in the exactly same position under exactly the same lighting
conditions with the operator being very careful not to shade the meters differently.
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