7640 User Manual
Contents
1. on Backlight always on The backlight uses a considerable amount of power the more it is used the less time the batteries will last MAINTENANCE The sensor windows should be kept clean and grease free Grease and finger marks that look clear may be opaque to UV Ensure that solvents do not come into contact with plastic parts especially the perspex window over the visible left hand sensor Battery The batteries should be replaced as soon as the battery symbol is seen on the bottom left of the display Any 1 1 to 2 5 volt AA style battery can be used though it is preferable to use alkaline cells because of their longer life and much reduced tendency to leak The battery compartment can be accessed by removing the single screw in the bottom centre of the case Suggested battery types 2 off required MANUFACTURER TYPE MN1500 Ever Ready LR6B4 Nickel Cadmium rechargeable types can be used but they cannot be charged inside the instrument Mains Power Supply The optional external mains power supply can be connected to the power input socket on the right hand side of the instrument This socket is only fitted if requested with order because the hole required compromises the moisture seal on the casing Software Version The internal software version is displayed when the 7640 is turned on A typical start up message might be ELSEC 7640 V2 1 in this case the software version is 2 1 CALIBRATION The c2. support and repairs contact Littlemore Scientific Engineering Gutchpool Farm Gillingham Dorset UK SP8 5QP Tel 01747 835550 Fax 01747 835552 Email support elsec co uk http www elsec co uk This equipment complies with EU Directive 2002 96 EC The symbol of the crossed container on the equipment shows that the product at the end of its useful life must be collected separately from other refuse When it is disposed of in the European Union it should be placed with other electronic waste at the place designated by the waste collection authority 10 SPECIFICATIONS Method of radiation detection Visible wavelength range Visible power range UV wavelength range UV power range UV proportion range Display resolution Accuracy Angular response Readout Date functions Batteries Battery Life External Power Supply If available Operating Temperature Dimensions Weight Twin silicon photodiodes connected to microprocessor 400 700nM CIE response No correction required for different light sources 0 1 200 000 Lux 0 1 20 000 Foot candles 300 400 nM 2 50 000 mW M 0 10 000 uW Lumen 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 uW Lumen Light 5 1 displayed digit UV 15 1 displayed digit Cosine Light amp UV 8 line graphical Liquid Crystal Display with automatic backlight Display as day month year or month
3. 7640 LIGHT amp UV MONITOR USER MANUAL NELSEC LITTLEMORE SCIENTIFIC ENGINEERING ELSEC Gutchpool Farm Gillingham Dorset UK Tel 44 0 1747 835550 Fax 44 0 1747 835552 Email elsec elsec co uk 7640 DOC V3 702 CONTENTS INTRO DUG TION ME 1 Geen CN 2 ET EE 2 UNITS OF MEASUREMENT EE 4 Ultra Violet UV EE 4 Visible ie EE 5 MAXIMUM AND MINIMUM 6 RIIT 7 EE 7 ler lre LE 7 MAINTENANCE a i ca in a cae as Sea Sad ee a oe E Rag 8 VAIO I EE EE 8 Malls Power Deier 8 SoftWare NEIE 8 CALIBRATION E 9 LIV Ge VISIBIG LIGNE Teicon edanean oaren ian ENE adunbseedba eontadamnbatats 9 ele EE 10 E E ERR Masies saana dnc a aa a dae call ene took ota sala 11 PRINTED 31 Aug 07 INTRODUCTION One of the primary responsibilities of the custodian of artworks and museum artefacts is to preserve them for future generations How they are stored and displayed is central to this the 7640 Environmental Monitor is an easy to use tool to help in achieving the safest long term protection 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 Using the 7640 measurements can be taken of the proportion of UV present as microwatts per lumen uW lumen the total amount of UV as milliwatts per square meter mW M and the amount of visible lig
4. alibration information is kept in non volatile EEPROM If this fails the instrument displays Mem Fail when turned on and will load default calibration values and future readings may be 25 in error If this happens a question mark is displayed on the top right of the display with suspect readings UV amp Visible Light The 7640 calibration should not drift with time but to be sure of accuracy the instrument can be returned to the manufacturer for a calibration check every 2 5 years The 7640 has a very carefully defined frequency response i e which wavelengths of light it is sensitive to Other light meters are often more sensitive to infra red light than they should be and so will give a higher reading with light sources that contain infrared e g ordinary filament light bulbs Because the 7640 has a cosine angular response it may give different readings to a type 762 which is relatively directional In other words the 7640 is more sensitive to light coming at an oblique angle than the 762 Note that the human eye has a logarithmic response this means that if two luxmeters are placed side by side they may give different readings even if it looks like they are getting a similar amount of light To compare the readings on 2 meters they each need to be placed in the exactly same position under exactly the same lighting conditions with the operator being very careful not to shade the meters differently SERVICE AND SUPPORT For
5. day year 2 off alkaline AA type Approx 100 Hours continuous use or 12 000 readings taking 30 seconds each Battery life will be less if the display backlight is used 4 0 5 2V DC 100mA A suitable mains power supply can be provided as an optional extra please specify mains voltage required 0 50 C 120 x 65 x 25mm 4 7 x 2 5 x 1 inches 160g 5 4 oz with batteries 11
6. fferent for some parameters and can be altered by the user if required see below Set Button The blue Set button is used to access advanced functions change units etc If it is pushed once a menu similar to that below is shown 2 Display gt Units gt Clock gt Calibrate gt The first menu item Max Min is highlighted different menu items can be highlighted using the ah and We buttons The wanted action is done by highlighting the appropriate menu item and pressing the Set button To abort without doing anything press the X button In some cases a further sub menu is displayed with more choices Elsewhere in this manual directions in the form Set item1 item2 are given This means Press Set select item in the first menu press Set again select item2 in the next menu and press Set To take a measurement without having to look at the display while the reading is taken for example where the operators head may effect the reading proceed as follows 1 Position the monitor where the reading is to be taken 2 Push the appropriate button for 1 2 seconds and release 3 Hold the monitor in position for at least 2 seconds 4 Without operating any buttons by mistake move the monitor so the reading can be noted before it turns itself off UNITS OF MEASUREMENT Ultra Violet UV Traditionally UV has been measured in museums as the proportion of ultraviolet present This result is useful for checking a particular
7. ht present Lux We always want to improve our products If you have any suggestions please send them to us BASIC OPERATION To take a reading the appropriate yellow button is pushed depending on the measurement required and the reading is taken UV Ultra Violet uW lumen or mW M Vis Visible light Lux or Foot candles The unit automatically turns off 10 seconds after the button is released unless a button is held down for over 5 seconds this will cause readings to be taken continuously until a button is pressed Note that the buttons should be pressed firmly for a second or so to ensure reliable operation Typical display A Lux B 1234 C Min 1 2 21 08 14 D Max 3456 14 09 34 E B H 3 11 06 10 20 Units of measurement Current reading Minimum reading since last reset day of month and time of minimum Maximum reading since last reset day of month and time of maximum Oe e H shows that the reading is held and the unit will turn itself off after 10 seconds of inactivity A round blob shows the unit is in continuous reading mode until a button is pushed nothing here means that a single reading is being taken The current time and date are also shown Unless they are hidden by pressing Set Clock Hide Unhide If a battery symbol appears at B it means that the batteries need to be replaced Min amp Max are reset by pressing Set Max Min Reset Press Set 3 times The above format is slightly di
8. 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 75uW lumen in museums and galleries though some organisations try to keep UV levels below 25uW lumen 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 M again some organisations keep the level below 6mW M Both the above units are displayed when the UV button is pressed one in large characters the other smaller at the bottom of the screen Which is displayed where can be swapped by pressing Set Units y W Lumn mW M2 Visible Light This can be displayed either in Lux or Foot candles To change the units press Set Units Lux Footcandl A visible light readout is provided to control illumination and limit damage done by visible light Normal museum light levels should be limited to 150 250 Lux Once measurements have been made the light level can be altered if necessary and UV filters can be fitted on windows fluorescent tubes or other UV producing light sources as required These filters often deteriorate over a period of years so it is essential to re check them periodically Magazine re
9. prints on the subject of museum lighting UV etc can be obtained from the manufacturer Suggested light levels for various other purposes are given below Corridor stairs etc 100 150 Lux Warehouses storage bays 100 150 Lux General office work 300 500 Lux Rough bench machine work 300 500 Lux Medium bench machine work 500 700 Lux Drawing offices 750 1000 lux Fine bench work 1000 1500 Lux Fine inspection 1500 3000 Lux Minute work 3000 5000 Lux MAXIMUM AND MINIMUM The maximum and minimum values for each unit are displayed along with the day of the month and time the maximum or minimum occurred The values can be reset by pressing Set Max Min Reset This equates to pressing Set 3 times To find the date when maxima amp minima occurred press Set Max Min Date or Time repeat to display the times again DISPLAY Contrast The display contrast can be increased decreased by pressing Set Display Contrast UP or DOWN If this is done the menu continues to be displayed and the set button can be pressed repeatedly until the required contrast is achieved Backlight The display backlight operation can be adjusted from the Set Display menu as follows Menu item Action Lamp off Backlight always off Lamp mostly off Backlight initially off turns on if visible light is less than 10 Lux Lamp mostly on Backlight is initially on turns off if visible light is more than 10 Lux Lamp
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