Irradian L202PMS Instruction Manual

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Handbook Ref No. MH100/Issue M
File Ref: L202vm.doc

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    
  1. Introduction
2. Specification
3. Cosine Angular Response
4. Operation
5. Maintenance and Calibration Description
6. Battery Replacement
7. Block Diagram
8. Programming via the RS232 interface
9. Environmental care, recycling and disposal

L202PMS Photometer Irradian Limited
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The Irradian L202PMS digital photometer is a portable instrument
designed for accurate measurement of illuminance in lux and screen
luminance in cd.m
-2
.
The photometer comprises of a hand held display unit, a detector with
connecting cable, a cosine corrected diffuser ring, a luminance contact
probe with shadow rings and an RS232 connection cable.
The display unit houses an autoranging amplifier, 4½ digit liquid crystal
display with back light illumination and PP3 type battery. The anodised
aluminium body houses the large area silicon photodiode, detector
amplifier, and specially selected colour filter glasses that adjust the
detectors response to closely match the CIE v(λ) photopic response. A
profiled diffuser ring gives the detector an accurate cosine corrected
angular response for illuminance measurements. The luminance probe
interchanges with the cosine diffuser ring to enable contact
measurements of CRT or LCD screen brightness. Shadow rings can be
fitted around the probe to reduce background lighting effects.
A switch within the detector housing automatically changes the
photometer calibration between lux and cd.m
-2
with an LED illuminated to
indicate which unit is selected.

Irradian Limited L202PMS Photometer
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DISPLAY UNIT
Ranges: 3 full scale autoranging decades measuring
from: 0 to 199.99 lux or cd.m
-2
and 0 to 1999.9 lux or cd.m
-2
and 0 to 19999 lux or cd.m
-2
Resolution 0,01 on range 1.
Accuracy: Measurement accuracy ±1digit with a
linearity error of <1% from 1 to 20 000.
Absolute calibration accuracy ±3% (illuminance),
±5% (luminance) @ 20°C traceable to
NPL standards.
Refer to Section 5 - Calibration Description.
Controls:
 Display backlight on off button.
Display backlight will switch off after a
programmable delay, factory setting 60 seconds.
HOLD/RUN Display is held at present reading until hold
button is pressed again.
 Power on / off button
ZERO Initiates a zero or background measurement
routine on all three ranges.
STORE Store the current reading
(holding up to maximum of sixteen values).
RECALL Display previously stored values.
STORE (On detector) See front panel store button.
Connectors: 8 pin mini DIN type detector connector.
3.5 mm socket RS232 connector.
Display: 4½ digit lcd display. Character pitch 10 mm.
Display illumination: An yellow / green large area LED back light
can be switched on to illuminate the display for
readings in low ambient light situations.
Power supply: PP3 type 9V battery.
Temperature range: 0 to 40°C. 80% RH.

L202PMS Photometer Irradian Limited
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Dimensions: 150 x 80 x 27mm. High impact polystyrene.
Weight: 400g including detector & battery.
DETECTOR
Model: DET202Vis
Detector: 60mm² silicon photodiode.
Linearity error: <1% from 1 to 19999
Temperature coefficient: -0.10 %/°C
Temperature range: Operation: -25 to +75°C
Storage: -45 to +100°C
Detector assembly: Black anodised aluminium alloy housing.
The detector is connected to the display unit via
a cable to a 8 pin mini DIN connector.
Spectral response: (Refer Figure 1). Coloured filter glasses adjust
the detectors response to closely match the CIE
v(λ) photopic response.
SPECTRAL RESPONSE
Figure 1. L202PMS Photometer with illuminance cosine ring

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ILLUMINANCE COSINE RING
Angular response: Accurately cosine corrected to Lamberts
Cosine Law. Maximum error is less than ±3.5%
from true response to 75°from normal
incidence, reference figure 2.
Screw thread: 1"1/8 x 20TPI.
LUMINANCE PROBE
Design: Aluminium tube 10mm φinternal diameter,
with aperture. Rubber O ring tip.
Screw thread: 1"1/8 x 20TPI.

L202PMS Photometer Irradian Limited
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The unit ‘lux’ is a measurement of the amount of light incident on a unit
area, (lumens.m
-2
). Any detector will measure this reliably when
measuring a beam of light perpendicular to the detectors surface,
however, when measuring scattered light or light from an extended
source the sensor must have an accurate response over its 180°field of
view. This response should be proportional to the cosine of the angle of
light incident on the detector, Lambert's Cosine Law. To ensure that the
integration of light from all angles is correct, the cosine diffuser fitted to
the front of the filter ring is profiled such that the angular response of the
detector decreases with cos(i) as the angle between the source and
detector increases from 0 to ±90°.
L202PMS
True Cosine Response
Figure 2
The cosine diffuser fitted to the detector is corrected to match the cosine
response to within ±3.5% up to angles of 75°. This ensures that the
meter accurately reads the light flux density whether it is measuring
scattered light (from an overcast sky) or a point source (a single lamp in
a dark room).

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SETTING UP
With the unit OFF, plug the detector connector into the socket on the top
of the display unit.
Note during operation the photometer may autorange the display
between the three range s as the measurement signal exceeds the
maximum or minimum measurement capability on each range.
ILLUMINANCE MEASUREMENTS
Ensure cosine diffuser ring is fully screwed onto the detector assembly
for illuminance measurements. Note, if the white cosine diffuser on the
filter ring is marked or dirty, clean before use. The lux LED must be
illuminated. Place the detector at the required measurement position
ensuring that the you do block any light onto the detector and record the
illuminance values.
LUMINANCE MEASUREMENTS
Remove the cosine diffuser ring and screw the luminance probe onto the
detector assembly. If required, slide a shadow ring onto the end of the
probe. The cd/m² LED must be illuminated. When measuring screen
luminance gently place the probe onto the CRT or LCD with the rubber
'O'ring uniformly touching the screen. The shadow ring can be moved to
touch the screen, thus removing any background reflections.
Note the area being measured by the probe, 9mm φ, must be uniform,
otherwise the meter will average the luminance from the part of the
screen being measured.
ZEROING THE PHOTOMETER
It is good practice to zero the photometer prior to use. Cover the
luminance probe or cosine ring and press the zero button. Continue
blocking the detector whilst the display shows - b g - (background). The
zero operation is complete when the display shows a reading of 00.00
(lux or cd/m²).