MARTINDALE LM90 User manual

MARTINDALE
ELECTRIC
Trusted by professionals
Martindale Electric Company Ltd was founded in 1928 and
manufactures a large range of electrical test equipment.
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Martindale Electric Company Limited
Martindale Electric Co Ltd,
Metrohm House, Imperial Park, Imperial Way, Watford,
Hertfordshire, WD24 4PP, UK
Tel: [phone] Fax: [phone]
E-mail: [email protected]
Website: www.martindale-electric.co.uk
E+OE. © Martindale Electric Co. Ltd. 2004
INSTRUCTIONS
LM90/92 LIGHTMETERS

Martindale Electric will carry out routine
calibration (on a chargeable basis) if the
instrument is returned, carriage paid, to
the address on the final page of this
document. Alternatively, a chargeable
collection and return service is available.
Repair & Service
There are no user serviceable parts in
this unit. Return to Martindale Electric
Company Ltd if faulty. Our service
department will promptly quote to repair
any faults that occur outside the
warranty period.
Storage Conditions
The unit should be kept in warm, dry
conditions away from direct sources of
heat or sunlight, with the battery
removed and in such a manner as to
preserve the working life of the unit. It is
strongly advised that the unit is not kept
in a tool box where other tools may
damage it.
INTRODUCTION
This instrument is a portable easy to use 3½ digit, compact digital lightmeter
designed for simple one hand operation. It provides measurements in lux and fc
units. The meter has a backlit LCD display, PEAK-HOLD (50m pulse light) and
DATA-HOLD features.
THIS MANUAL COVERS MODELS LM90 & LM92
SAFETY INFORMATION
Read the safety and operation instructions before using the lightmeter.
SPECIFICATIONS
GENERAL
Display: 3½ digit liquid crystal display (LCD) with maximum reading of 1999
Over range: (OL) is displayed
Low battery indication: the " " is displayed when the battery voltage drops
below the operating level
WARNING
• To avoid electric shock, do not operate this product in wet or damp
conditions.
• To avoid injury or fire hazard, do not operate this product in an explosive
atmosphere.
• To avoid eye injury, wear eye protection if there is a possibility of exposure
to high-intensity rays.
• Do not immerse in liquids, clean the sensor head using only a damp cloth.
• Cover sensor head when not in use to extend silicon photodiode sensor
life.
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Warranty
Faults in manufacture and materials are fully guaranteed for 2 years from date of
invoice and will be rectified by us free of charge, provided the unit has not been
tampered with and is returned to us with its housing unopened. Damage due to
dropping, abuse or misuse is not covered by the guarantee. Nothing in these
instructions reduces your statutory rights.

Measurement rate: 2.5 times per second, nominal.
Operating Environment: 0°C to 50°C (32°F to 122°F) at< 70% relative humidity
Storage Temperature: -20°C to 60°C (-4°F to 140°F), 0 to 80% R.H. with battery
removed from meter
Accuracy: Stated accuracy at 23°C ± 5°C (73°F ± 9°F), <70% relative humidity
Battery: Standard 9V battery (NEDA 1604, IEC 6F22 006P)
Battery Life: 200 hours typical with carbon zinc battery
Dimensions (HxWxD): 190mm(H) x 65.5mm(W) x 35mm(D)
Weight: 210g including battery
ELECTRICAL
Photometric Formulas:
10.764·footcandles=lux(lumens/meter2)
0.0929·lux=footcandles(lumens/foot 2)
Range LM90: 20lux, 200lux, 2000lux, 20klux
20fc, 200fc, 2000fc, 20kfc
Range LM92: 200lux, 2000lux, 20klux, 200klux
200fc, 2000fc, 20kfc, 200kfc
Resolution: 0.1lux, 0.1fc
Spectral response: CIE photopic
Acceptance angle: ƒ'2<3% cosine corrected (150°)
Total accuracy for CIE standard illuminant A (2856K): ±(3%rdg + 10dgts)
Temperature Coefficient: 0.1x (specified accuracy)/°C (<18°C or >28°C),
0.056x(specified accuracy)/°F(<64.4°F or >82.4°F)
Peak Hold response time: >50mS pulse light.
CIE Photopic Curve
SEE TABLE ON NEXT PAGE
OPERATOR MAINTENANCE
Battery Replacement
Power is supplied by a 9 volt "transistor" battery. (NEDA1604, IEC 6F22). The
" " appears on the LCD display when replacement is needed. To replace the
battery, remove the two screws from the back of the meter and lift off the battery
cover. Remove the battery from the battery contacts.
The CIE photopic curve is an international standard for the colour response of
the average human eye
CIE standard illuminant A can be realised by means of CIE standard source A,
which is defined as: A gas-filled tungsten-filament lamp operating at a
correlated colour temperature of 2856K
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6

OPERATING INSTRUCTIONS
Push buttons
Peak-Hold Switch:
Press "PEAK" button to toggle in and out of the PEAK-HOLD mode. The " "
indicator is displayed. (Response Time: >50mS)
Display Back-Light Button
Pressing " " button to turn on the Back-Light.
Pressing " " button to turn off the Back-Light.
HOLD (DATA-HOLD) Button
Press "HOLD" button to toggle in and out of the DATA-HOLD mode. In the
DATA-HOLD mode, the " "indicator is displayed and the last reading is held
on the display.
OPERATION
1. Set the function switch to the desired lux or fc units.
2. Remove the sensor head cover.
3. Hold the sensor head steady and make certain that the light source
completely fills the cosine correction dome.
4. Move away from the sensor head to avoid shadowing it. The sensor head
has a 1.5 meter cable to allow separation between the observer and the
measurement location.
5. Read the illuminance value from the display. If magnitude of lux (or fc) is not
known, set RANGE switch to the highest range and reduce until a satisfactory
reading is obtained.
6. Cover sensor head to extend sensor life.
SPECIAL CONSIDERATIONS
• Keep the plastic domed cosine corrector clean and free of scratches. It may
be cleaned with a soft cloth and isopropyl alcohol.
• When light is received from many directions simultaneously, take special care
to avoid reflections or shadowing the sensor with your body.
• For best accuracy, repeat the measurement several times to ensure that the
light source has remained stable.
• Avoid flexing the cable excessively at either end of the cable.
• The Inverse-square Law
The law states that the illuminance E at a point on a surface varies directly with
the intensity I of a point source, and inversely as the square of the distance d
between the source and the point. If the surface at the point is normal to the
direction of the incident light, the law is expressed by E=I/d2.
• Cosine Law
The law that the illuminance on any surface varies as the cosine of the angle of
incidence. The angle of incidence θis the angle between the normal to the
surface and the direction of the incident light. The inverse-square law and the
cosine law can be combined as E=(I cos θ)/d2.
Cleaning
Periodically wipe the case with a damp cloth, do not use abrasives or solvents.
P
H
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