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A single instrument enables measurement of the three types of radiation that are of most interest: visible (Lux), thermal radiation and ultraviolet. The 774 also measures temperature in °C or °F.
Thermal Radiation (IR)
The measurement of thermal radiation
(shown as W/M2 or btu/hour/ft2) 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
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.
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 774, measurements can be taken of the proportion
of UV present (mW/lumen), the total amount of UV (mW/M2)
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 774 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 774 to be left taking readings for months at a time. Software is
provided to display the measurements and save the logged data in CSV format
that can be accessed and displayed by many programs (e.g. Microsoft Excel).
Easy to use
Much trouble has been taken to make the 774 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 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.
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.
| Visible wavelength range | 400-700nM (CIE response). No correction required for different light sources. |
| Visible power range | 0.1 - 200,000 Lux (0.1 - 20,000 Foot-candles) |
| UV wavelength range | 300 - 400 nM |
| UV power range | 2 - 50,000 mW/M2 |
| UV proportion range | 0 - 10,000 mW/Lumen |
| Thermal radiation sensor | Bismuth/Antimony thermopile with KBr window |
| IR/Thermal wavelength range | 350nM - ~40µM |
| Thermal radiation range | 0-1000 W/M² |
| Display resolution | Lux: 0.1 up to 100 then 1 Foot-candles: 0.1 up to 100 then 1 UV: 0.1 up to 100 then 1 Proportion of UV: 1 mW/Lumen Temperature: 0.1°C or °FIR: 0.1 up to 100 then 1 |
| Accuracy | Visible: 5% ±1 displayed digit IR: 5% ±10W/M2 UV: 15% ±1 displayed digit Temperature: ±0.5°C (±0.9°F) |
| Angular response (Light, UV & IR) | Cosine |
| Readout | 8 line graphical Liquid Crystal Display with automatic backlight |
| Data logging time intervals(Time till full) | 10 seconds (30 hours), 1 minute (7½ days) , 10 minutes (75 days),1 hour (454 days) |
| Data logging storage capacity | 10,900 readings of all 4 parameters |
| Computer Interface | IrDA compatible wireless infra-red link. |
| Date functions | Display as day-month-year or month-day-year. Fully Year 2000 compliant. |
| Batteries | 2 off alkaline AA type. |
| Battery Life | Approx 100 Hours continuous use or 12,000 readings taking 30 seconds each. Battery life will be less if the display backlight is used |
| External Power Supply(If available) | 4.0-5.2V DC, 100mA A connection for an external supply is provided to special order at extra cost. |
| Operating Temperature | 0-50°C |
| Dimensions | 150 x 65 x 25mm 5.9 x 2.5 x 1 inches Including IR/Temperature probe |
| Weight | 165g (5.6 oz) with batteries. |
Gutchpool Farm, Gillingham, Dorset,
UK
Tel: (01747) 835550 Fax: (01747) 835552
International Tel: +44
1747 835550 Fax: +44 1747 835552
elsec@elsec.co.uk