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775C Visible (Lux), Thermal Radiation and Ultraviolet Meter with Logging
A single instrument enables measurement of the three types of radiation that are of most interest: visible (Lux), thermal radiation and ultraviolet. The ELSEC 775C light meter 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 recognized 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 ELSEC 775C light meter, 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 ELSEC 775C light meter 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 775C 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
Great effort has been taken to make the ELSEC 775C light meter 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.
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Specifications
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Visible wavelength range:
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400-700nM (CIE response). No correction required for different light sources.
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Visible power range:
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0.1 - 200,000 Lux (0.1 - 20,000 Foot-candles)
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UV wavelength range:
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300 - 400 nM
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UV power range:
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2 - 50,000 mW/M2
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UV proportion range:
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0 - 10,000 mW/Lumen
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Thermal radiation sensor:
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Bismuth/Antimony thermopile with KBr window
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IR/Thermal wavelength range:
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350nM - ~40µM
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Thermal radiation range:
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0-1000 W/M²
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Display resolution:
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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
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Accuracy:
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Visible: 5% ±1 displayed digit
IR: 5% ±10W/M2
UV: 15% ±1 displayed digit
Temperature: ±0.5°C (±0.9°F)
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Angular response (Light, UV & IR):
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Cosine
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Readout:
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8 line graphical Liquid Crystal Display with automatic backlight
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Data logging time intervals(Time till full):
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10 seconds (30 hours), 1 minute (7½ days) , 10 minutes (75 days),1 hour (454 days)
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Data logging storage capacity:
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10,900 readings of all 4 parameters
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Computer Interface:
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IrDA compatible wireless infra-red link.
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Date functions:
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Display as day-month-year or month-day-year. Fully Year 2000 compliant.
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Batteries:
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2 off alkaline AA type.
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Battery Life:
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Approx 100 Hours continuous use or 12,000 readings taking 30 seconds each. Battery life will be less if the display backlight is used
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External Power Supply (If available):
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4.0-5.2V DC, 100mA A connection for an external supply is provided to special order at extra cost.
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Operating Temperature:
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0-50°C
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Dimensions:
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150 x 65 x 25mm (5.9 x 2.5 x 1 inches) Including IR/Temperature probe
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Weight:
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165g (5.6 oz) with batteries.
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