Elsec 775 – Universal Light & Thermal Radiation Meter

This single instrument enables measurement of four parameters that cause damage to buildings, valuable objects, documents etc. The Elsec 775 series enables the measurement of ultraviolet light, visible light, thermal radiation (infrared), and temperature. The handheld meter is ideally suited to the conservation of buildings, art and other valuable objects in museums and galleries.

The 775 measures and displays UV light (mW/M² or µW/lumen), visible light (lux or foot-candles), thermal infrared (W/M²), and temperature (°C or °F) for testing heat reflective coatings on windows. The 775 is the same as the 765 except the RH sensor has been replaced by a thermal infrared sensor.

The 775C (with logging) is the same as 775 with data logging capacity for over 70,000 readings of all four parameters. No special software is required, logged information is stored on an internal USB Flash disc and the data can be downloaded onto a PC and viewed with any spreadsheet (Excel etc). A free application (RView) is also available for download that displays the data as a zoomable graph that can be saved as an image for inclusion in documents and/or printed.

Parameters

Ultraviolet (UV)

For many years it has been recognised that one of the major causes of damage to museum objects and other sensitive objects, soft furnishings etc is the fading and rotting effect of light on the object. The most damaging part of the illumination is its ultraviolet content. Since 1976 Littlemore Scientific (ELSEC) has been providing instruments that enable the conservator to measure the UV content of light and thereby protect valuable exhibits. Using the 775, measurements can be taken of the proportion of UV present (mW/lumen), the total amount of UV (mW/M²).

Visible Light

The amount of visible light is important, not only to check illumination in work areas, galleries etc but also to control damage to light-sensitive objects that is also caused by normal light. Measurements can be displayed as Lux or Foot-candles.

Thermal Radiation (IR)

The measurement of thermal radiation (shown as W/M2) allows the user to estimate how much solar heat is coming through windows, check the performance of heat-reflecting films, measure the heating effect of lamps on objects etc.

Easy to use

Much trouble has been taken to make the 775 as easy to use as possible. Anyone can take measurements straight out of the box with little, if any, reference to the instruction manual. The appropriate button is pushed depending on the measurement required and the reading is taken. The unit automatically turns off 20 seconds after the last reading unless a button is held down for over 3 seconds, this causes continuous measurements to be taken until another button is pressed. The large OLED display enables an easy to use the menu system to select the more advanced functions, change units etc.

Units of measurement for UV

Traditionally UV has been measured in museums as the proportion of ultraviolet present. This result is useful for checking a particular lamp or window because the proportion of UV does not change with the distance from the light source. Using a simple rule, the amount of UV on an object can be limited (it is usual to arrange that the proportion of UV should not exceed 75mW/lumen in museums). The damage is done by the total amount of UV falling on the object, so it is useful to be able to measure this directly, especially if non-standard amounts of illumination are required. The amount of UV should be as little as possible but in general, should not exceed 20mW/M2.