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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 recognised 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.
Much trouble has been taken to make the 764 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. Click here for more information on displays and menus.
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 seperate program allows the graphical display of the data. Click here for more information on logging software.
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.
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Method of radiation detection |
Twin silicon photodiodes connected to single chip microprocessor |
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Visible wavelength range |
400-700nM (CIE response). No correction required for different light sources |
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Visible power range |
0.1 - 200,000 Lux (0.1 – 20,000 Foot-candles) |
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UV wavelength range |
300-400 nM |
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UV power range |
2 - 50,000 mW/sqM |
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UV proportion range |
0 - 10,000 mW/Lumen |
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RH sensor |
Capacititive film type |
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RH range |
0-100%RH |
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Display resolution |
Lux: 0.1 up to 100 then 1 |
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Accuracy |
Light: 5%
± 1 displayed digit UV: 15% ± 1 displayed digit Temperature: ± 0.5° C (± 0.9° F) RH: ± 2.5% |
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Angular response (Light & UV) |
Cosine |
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Readout |
8 line graphical Liquid Crystal Display with automatic backlight |
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Data logging time intervals (Time till full) |
10 seconds (30 hours), 1 minute (7½ days) , 10 minutes (75 days), 1 hour (454 days) |
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Data logging storage capacity |
10,900 readings of all 4 parameters |
| Storage resolution for logged data | Light &
UV: 0.1% of saved value Temperature: 0.5°C Humidity: 0.5%RH |
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Computer Interface |
IrDA compatible wireless infrared link |
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Date function |
Display as day-month-year or month-day-year. Fully Year 2000 compliant |
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Batteries |
2 off alkaline AA type |
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Battery Life |
Approx 100 Hours continuous use or 12,000
readings taking 30 seconds each. |
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External Power Supply |
4.0-5.2V DC, 100mA A suitable mains power supply can be provided as an optional extra (please specify mains voltage required). |
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Operating Temperature |
0-50° |
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Dimensions |
150 x 65 x 25mm 5.9 x 2.5 x 1 inches Including RH/Temperature probe |
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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
