Irradian PR450 Instruction Manual
Handbook Ref No. MH096/Issue G
File Ref: PR450_G.doc
1 Introduction
2 Specification
3 Operation
4 Irradiance Measurements
5 Cosine Angular Response
6 Calibration Description
7 Care and Maintenance
8 Optional Accessories
9 Block Diagram
10 Environmental Care, Recycling and Disposal
PR450 Phototherapy Radiometer Irradian Limited
1
The Irradian portable phototherapy radiometer model PR450 is designed
specifically to measure directly the irradiance of blue light for the
treatment of hyperbilirubinaemia in new born babies.
The photodiode and colour glass filters are designed to give a spectral
response closely matching the bilirubin phototherapy action spectrum.
Good blocking of the detectors response outside the bandpass ensures
the radiometer does not measure non-therapeutic light. The cosine
corrected diffuser input ensures accurate measurements where ever the
light source.
Note: The PR450 is NOT an ultra violet radiometer and should NOT be
use to measure the output of ultra violet lamps in UV phototherapy
treatment.
Irradian Limited PR450 Phototherapy Radiometer
2
RADIOMETER
Range: 0 - 199.99 µW/cm²/nm
Monochromatic Cal. The radiometer with detector / filter is
calibrated with a 450nm monochromatic
source.
Spectroradiometric Cal. The radiometer with detector / filter is
calibrated to match the measurement of a
spectroradiometer for a particular source,
e.g. phototherapy halogen lamp or photo-
therapy fluorescent lamp.
Accuracy Absolute calibration accuracy ±7.5% traceable to
NPL standards.
DISPLAY UNIT PR450X
Controller: 80C51 based 8bit micro-processor with a
3.6864MHz clock.
Memory On board non volatile RAM for calibration
factors and set-up parameters.
Integration Time 0.33s.
Conversion Scale 17 bit.
Conversion Accuracy: Measurement accuracy ±1digit with a
linearity error of <1%.
Display: 4½ digit lcd display. Character height 10mm.
Power Supply: 9 volt 1200mAh, PP3 battery.
Power Consumption: Shut down mode <5µA.
Operating 10 - 20mA.
Battery Life ~ 50 hours.
PR450 Phototherapy Radiometer Irradian Limited
3
(continued):
Temperature Range: 0 to 40°C. 80% RH.
Dimensions: 150 x 80 x 45mm.
High impact polystyrene.
Weight: Approximately 270g.
Front Panel Controls:
ZERO Initiates a zero or background measurement
Routine.
HOLD/RUN Display is held at present reading until HOLD
button is pressed again.
Power on / off button.
Connector: 8 pin mini DIN type detector connector.
6 pin mini DIN type RS232 connector for factory use only.
Irradian Limited PR450 Phototherapy Radiometer
4
(continued):
DET201450 DETECTOR
Amplifier PCB Photodiode
Cable
Glass Filters
Cosine Diffuser
The DET201450 detector comprises of an aluminium housing,
photodiode, R450 filter and PCB assembly.
Detector: 5.2 mm² High stability GaAsP photodiode.
Spectral Response: Refer Figure 1.
Angular Response: Accurately cosine corrected to Lambert's
Cosine Law. Maximum error is less than ±5%
from true response to 70° from normal
incidence, reference Section 5.
Temperature Coefficient: <0.3 %/°C.
Amplifier Gain 5x10
5
V/A.
Current to Frequency 0 - 0.5Mhz.
Linearity Error: <1% across range.
Temperature Range: Operation: -10 to +60°C.
Storage: -20 to +70°C.
Detector Housing: Black anodised aluminium alloy housing.
Cable: 1 metre cable to 8 pin mini DIN type connector.
Weight: Approximately 140g.
PR450 Phototherapy Radiometer Irradian Limited
5
(continued):
DET201450 Detector
Typical Spectral response
0
10
20
30
40
50
60
70
80
90
100
400 415 430 445 460 475 490 505 520 535 550
R
e
s
p
o
n
s
e
%
Wavelength (nm)
Figure 1
Irradian Limited PR450 Phototherapy Radiometer
6
SETTING UP
1) With the unit OFF, plug the detector 4 way connector into the socket
on the top of the display unit.
2) Press and release the power switch on the PR450 display key pad.
The microcontroller will initiate, the display momentarily showing:-
The radiometer display will now change to show the units value. A
typical display is shown below.
3) It is recommended that the radiometer amplifier is nulled periodically.
Place the cover over the detector. Press and release the ZERO switch,
the display will momentarily show:-
4) The micro controller will now measure the amplifier offset and store
this value in the non volatile memory. All subsequent measurements
will first have this offset subtracted before displaying the
measurement.
At the end of the sequence the display will show:-
5) Remove the light cover from the detector. The equipment is now ready
for use.
6) At any time the measurement process can be halted by pressing the
HOLD/RUN button. Pressing the button once again will resume the
measurement process.
PR450 Phototherapy Radiometer Irradian Limited
7
IT IS IMPORTANT TO NOTE THAT THE PR450 IS A BLUE LIGHT
PHOTOTHERAPY RADIOMETER AND NOT SUITABLE FOR THE
MEASUREMENT OF ULTRA VIOLET LAMPS.
IRRADIAN OFFER A RANGE OF ULTRA VIOLET RADIOMETERS
INCLUDING THE UV201, UV202 AND UV203.
Irradiance is the measurement of radiometric light per unit area, watts
per metre, W/m
-2
(spectral irradiance µW/cm²/nm). The part of the
spectrum to be measured is defined by the filter fitted onto the detector.
Ideally this should be a filter with a square spectral response. In practice
it rarely is and the filter is defined with a peak response wavelength and a
full width half maximum, FWHM bandwidth. In all applications it is vital to
know the part of the spectrum being measured by the detector and filter,
and if possible to know the spectrum of the light source. In addition the
radiometer should be calibrated to best suit the measurement conditions.
It may even be necessary to have more than one calibration factor for the
same detector / filter combination.
For most applications the measurement plane is horizontal and a cosine
corrected diffuser is fitted to the front of the detector assembly. If the
working surface is not horizontal then placing the detector on or parallel
to the worktop is a more representative measurement of irradiance.
Note that all the light sources in the hemisphere above the detector will
contribute to the measurement. The sources may be obvious, lamps or
windows or even walls or other reflecting surfaces. Take care not to
shadow the detector during all measurements.
For routine measurements of a phototherapy lamp it is necessary to
record the distance to the lamp, the position of the detector with respect
to the lamp and the orientation of the detector.
Irradian Limited PR450 Phototherapy Radiometer
8
Irradiance (or spectral irradiance) is a measurement of the amount of
light incident on a unit area (watts/m²) (or /nm for spectral irradiance).
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. More importantly, this
response should be proportional to the cosine of the angle of light
incident on the detector. This comes from the fact that the projected area
of any surface at an angle of i is proportional to cos(i).
To ensure that the integration of light from all angles is correct, the
cosine diffuser matches the angular response so that response of the
detector decreases with cos(i) as the angle between the source and
detector increases from 0 to 90°.
DET201450
True Cosine Response
Figure 4
Irradian's cosine diffusers are corrected to match the cosine response to
within ± 5 % up to angles of 70°. This ensures that the meter correctly
reads illuminance or visible light flux density whether it is measuring light
from an extended or a point source.
PR450 Phototherapy Radiometer Irradian Limited
9
Irradian holds a number of tungsten halogen and deuterium lamps and
silicon photodiode standards which are routinely calibrated by the
National Physics Laboratory in the UK.
Four methods for calibrating the radiometer are available:
i) Radiometric calibration with monochromatic light at 450nm in units of
W/m
2
.
ii) Radiometric calibration with monochromatic light at 450nm, the
sensitivity is then divided by the bandwidth at FWHM to give a
calibration in units of W/m
2
/nm.
iii) Spectroradiometric calibration. Light source is scanned with a
spectroradiometer between 425 and 475nm. The total integrated
irradiance is then recorded and divided by the spectral range to give
calibration in units of µW/cm²/nm with the PR450 radiometer
calibration adjusted to match the spectroradiometer.
iv) Each spectroradiometric value in (iii) can be adjusted with the
action spectrum to form a weighted irradiance with the PR450 set to
match this.
Note the spectroradiometric calibrations are dependent on the light
source. It may be necessary to use correction values if accurate
measurements are required for both fluorescent and discharge type
lamps.
As with all measuring equipment a routine calibration is recommended,
typically annually, but with frequent use by a number of different users a
shorter recalibration period may be necessary.
Irradian Limited PR450 Phototherapy Radiometer
10
1) The PR450 display unit can be cleaned using a moist cloth with
detergent. Do not use solvent or alcohol to clean surfaces.
2) The diffuser on each filter ring should be kept clean at all times.
3) The radiometer is a precision instrument, protect from shocks.
4) Avoid supporting the detector by the multi core cable.
The following items are available from Irradian:
•Leveling Plate (Three adjustable feet and built in spirit bubble).
•Extension cables.
PR450 Phototherapy Radiometer Irradian Limited
11
Diffuser
Filter
Detector
Amp v to f Counter
µController
Keypad
Liquid Crystal
Display
Display Driver
Detector Amplifier
Micro-Controlled Display Unit
Non Volitile RAM
Irradian Limited PR450 Phototherapy Radiometer
12
! "
! " ! "
! " #
##
#
The purpose of the European Commission WEEE directive (Waste
Electrical and Electronic Equipment; 2002/96/EC) is to ensure that
electrical and electronic products are recycled using the best treatments,
recovery and recycling techniques that are currently available. This is so
that high health standards and a lasting environmental protection can be
achieved and maintained.
This product has been designed and manufactured using high quality
materials and components, many of which can be recycled and reused.
Please remember to observe the local regulations that govern both the
disposal of the packaging materials accompanying this product and any
used batteries.
DO NOT DISPOSE OF THIS PRODUCT IN YOUR
GENERAL WASTE BIN.
Please inform yourself about your local WEEE collection
system which is available for electrical and electronic
products that are marked with the symbol shown here.
When disposing of this meter, please use one of the following options:
1) Use your local designated WEEE collection facilities to dispose of the
complete product (including cables, detectors, filters & accessories).
2) Return the complete product back to Irradian, marking it clearly as
intended for WEEE disposal.
$%&
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9 Elphinstone Road Telephone: +44 (0)1875 898-083
Tranent Facsimile: +44 (0)1875 616-528
Scotland EH33 2LG Web: www.irradian.co.uk
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