Replaces
4 separate instruments!
Ultra
Violet (UV) level
Visible
Light (Lux or Foot-candles)
%
Relative Humidity
Dew
point
Temperature
(°C or °F)
Pocket Sized
Easy
one-handed operation
Large,
easy to read display
Maximum
& minimum with time
Optional
data logging
This single
instrument enables measurement of the four parameters that cause most
damage to buildings, valuable objects, documents etc: ultra-violet and
visible radiation, humidity and temperature.
For many years it
has been recognized that one of the major causes of damage to museum
objects and other antiquities is the fading and rotting effect of light
on the object. The most damaging part of the illumination is its
ultraviolet (UV) 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 764,
measurements can be taken of the proportion of UV present (mW/lumen),
the total amount of UV (mW/M²), the amount of visible light present as
Lux or Foot-candles. Temperature can be measured in °C or °F, humidity
is shown as % Relative Humidity (%RH) and dew point. The displayed units
can easily be changed by the user.
Provision is made
for user calibration of the RH sensor using saturated salt
solutions. A calibration kit is available as an optional extra.
Maximum and
minimum values and their time of measurement are displayed for each
parameter.
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 10 seconds after the last reading unless a
button is held down for over 5 seconds, this causes continuous
measurements to be taken until another button is pressed. The large 8
line display enables an easy to use menu system to select the more
advanced functions, change units etc.
Data Logging
The optional
data-logging function enables over 10,000 readings of all four
parameters to be automatically taken at selectable intervals (every 10
seconds to 1 hour). The saved data can then be transferred to a computer
by a wireless infra-red link (IrDA compatible). Many modern computers
have an infra-red interface built in; for those that do not, adapters
are available. When logging data the 764 can be turned off to save power
and the built in clock will turn the unit on whenever a reading needs to
be taken, this enables a 764 to be left taking readings for months at a
time. Software is provided to save the logged data in a CSV format that
can be accessed and displayed by many programs (e.g. Microsoft Excel). A
separate program allows the graphical display of the data.
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 actual amount of damage done is
determined 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.
A Lux readout is
provided to control illumination and limit damage done by visible light.
Normal museum light levels should be limited to 150-250 Lux.
