Delta OHM LPPHOT01 Photometric/Radiometric Probes User Manual
- June 5, 2024
- Delta OHM
Table of Contents
Delta OHM LPPHOT01 Photometric/Radiometric Probes
INTRODUCTION
The probes of the series LP…01 allow measurement of photometric and radiometric quantities such as illuminance (lux), irradiance (W/m2) across VIS-NIR, UVA, UVB, UVC spectral regions, the number of photons per time unit and area in the PAR region (400 nm…700 nm).
In probes LP….01 there is no need for external power supply. The output signal
in mV is given through a resistor shunting the photodiode ends. The
photocurrent generated by the photodiode when hit by light, is converted to a
potential difference, which is read by a voltmeter. Once the DDP (Potential
Difference) is known, the measured value can be calculated through the
calibration factor.
Each probe is individually calibrated. The sensitivity factor is marked on
the housing of the probe and is specific to that probe.
LPPHOT01 and LPPAR01 probes are equipped with cosine corrected diffuser.
LP…01 probes are suitable for indoor applications which requires the constant
monitoring of the quantities specified.
The output signal can be amplified or converted into a 4…20 mA or 0…10 Vdc
signal by using a converter of the series HD978TR3 (4…20 mA) or HD978TR4 (0…10
Vdc) DIN rail attachment, or the wall mounting types HD978TR5 (4.…20 mA) and
HD978TR6 (0…10 Vdc).
PROBES TECHNICAL CHARACTERISTICS
All probes are composed of a photodiode, a filter, a diffuser, the case and a
5 meters cable allowing the connection of the probe to the reading instrument.
The typical variation of probe sensitivity with temperature variation is
-0.1%/oC. The sensitivity factor shown on the probe was obtained in an air-
conditioned environment at an ambient temperature of 23 °C and relative
humidity 50 ±10 %.
LPPHOT01
The LPPHOT01 probe (class B luxmeter) measures illuminance (lux) defined as
the ratio between the luminous flux (lumen) passing through a surface and the
surface area (m2).
The spectral response curve of a photometric probe is equal to the one of the
human eye, known as standard photopic curve V(λ).
The difference in spectral response between LPPHOT01 and the standard photopic
curve V(λ) is calculated by means of the error f1’.
Photometric characteristics
The spectral response curve of the LPPHOT01 probe is shown in the following
graph together with the standard phototypical curve. 
The calibration of the probe is performed by comparing it to a
luxmeter calibrated by a Primary Metrological Institute. The calibration
procedure follows the CIE publication No 69 (1987) “Method of Characterizing
Illuminance Meters and Luminance Meters” and is carried out by illuminating
the probe with a standard illuminant A.
The illuminant A is a reference incandescent lamp with a colour temperature of
2856K.
The following figure shows the trend of the deviation from the cosine law as
the angle varies for the LPPHOT01 probe: 
Technical specifications
| Typical sensitivity | 0.5…1.5 mV/klux |
|---|---|
| Measuring range | 0…200000 |
| Spectral range | V(λ) |
| Calibration accuracy | <4% |
| f’ 1 (V(λ) match error) | <6% |
| f 2 (cosine response/directional error) | <3% |
| f 3 (linearity) | <1% |
| F 5 (fatigue) | <0.5% |
| Operating temperature | 0…50°C |
| Output impedance | 0.5…1 kΩ |
| Dimensions | Ø 30 mm x 38 mm height |
LPRAD01
The LPRAD01 probe measures irradiance (W/m2) defined as the ratio between the flow of energy (W) crossing a surface and the area of the surface considered (m2) in the spectral region of the VIS-NIR (400 nm…1050 nm).
Photometric characteristics
The spectral response curve of the LPPOHT01 probe is shown in the following
graph together with the standard phototypical curve.
Probe calibration is carried out by using 577/579 nm lines of a Xe-
Hg lamp, filtered through a special interferential filter. The temperature has
a negligible influence on the spectral response of the probe.
Technical specifications
| Typical sensitivity | 2.6 μV/μW/cm-2 |
|---|---|
| Measuring range | 0…200 mW/cm2 |
| Spectral range | ≈400 nm…≈1050 nm |
| Calibration accuracy | <6% |
| f 2 (cosine response/directional error) | <6% |
| Operating temperature | 0…50°C |
| Output impedance | 1 kΩ |
| Dimensions | Ø 30 mm x 38 mm height |
LPPAR01
The LPPAR01 probe measures the ratio between the number of photons that strike a surface in one second, in the 400 nm…700 nm spectral range and the surface area (m2). This quantity is defined as PAR: Photosynthetically Active Radiation.
Radiometric characteristics
The spectral response curve of the LPPAR01 probe is shown in the following
graph:
The probe calibration is carried out
by using an halogen lamp, with a known spectral irradiance in a specific
spectral range (400 nm…700 nm).
Technical specifications:
| Typical sensitivity | 30 μV/μmol·m-2s-1 |
|---|---|
| Measuring range | 0…5000 μmol·(m-2s-1) |
| Spectral range | 400 nm…660 nm |
| Calibration accuracy | <6% |
| f 2 (cosine response/directional error) | <6% |
| Operating temperature | 0…50°C |
| Output impedance | 1 kΩ |
| Dimensions | Ø 30 mm x 38 mm height |
LPUVA01
The LPUVA01 probe measures irradiance (W/m2) defined as the ratio between the radiant flux (W) passing through a surface and the surface area (m2) in the UVA (315 nm…400 nm) spectral range. Thanks to a new type of photodiode, LPUVA01 is blind to visible and infrared light.
Radiometric characteristics
The spectral response curve of the LPUVA01 probe is shown in the following
graph:
The calibration is performed by
reference to our primary standard with monochromatic light at 365 nm obtained
separating the emission line of a Xe-Hg lamp with an inferential filter. To
get best performances from your LPUVA01 it is strongly recommended that the
calibration be checked annually. The temperature has a negligible influence on
the spectral response of the probe.
Technical specifications
| Typical sensitivity | 2.6 μV/μW/cm-2 |
|---|---|
| Measuring range | 0…200 mW/cm2 |
| Spectral range | peak at ≈360 nm and FWHM 60 nm |
| Calibration accuracy | <6% |
| Operating temperature | 0…50°C |
| Output impedance | 1 kΩ |
| Dimensions | Ø 30 mm x 38 mm height |
LPUVB01
The LPUVB01 probe measures irradiance (W/m2) defined as the ratio between the radiant flux (W) passing through a surface and the surface area (m2) in the UVB (280 nm…315 nm) spectral range. Thanks to the use of a new type of photodiode, the LPUVB01 probe is blind to visible and infrared light. Radiometric characteristics
The spectral response curve of the LPUVB01 probe is shown in the following
graph:
Probe calibration is carried out by
using a 313 nm line of a Xe-Hg lamp, filtered through a special interferential
filter. Measurement is carried out by comparison with the primary standards,
assigned to Delta OHM Metrological Laboratory.
Technical specifications
| Typical sensitivity | 0.19 μV/(μW/cm2) |
|---|---|
| Measuring range | 0…200 mW/cm2 |
| Spectral range | peak at ≈305 nm and FWHM 31 nm |
| Calibration accuracy | <8% |
| Operating temperature | 0…50°C |
| Output impedance | 2 kΩ |
| Dimensions | Ø 30 mm x 38 mm height |
LPUVC01
The LPUVC01 probe measures irradiance (W/m2) defined as the ratio between the radiant flux (W) passing through a sur-face and the surface area (m2) in the UVC (200 nm…280 nm) spectral range. Thanks to the use of a new type of pho- todiode, the LPUVC01 probe is blind to visible and infrared light.
Radiometric characteristics
The spectral response curve of the LPUVC01 probe is shown in the following
graph:
The probe calibration is carried
out by measuring irradiance coming from an Hg lamp at 254 nm.
Technical specifications
| Typical sensitivity | 0.25 μV/(μW/cm2) |
|---|---|
| Measuring range | 0…200 mW/cm2 |
| Spectral range | peak at 260 nm and FWHM 32 nm |
| Calibration accuracy | <10% |
| Operating temperature | 0…50°C |
| Output impedance | 2 kΩ |
| Dimensions | Ø 30 mm x 38 mm height |
INSTALLATION
Once the installation place has been decided, the connections between the probe and the voltmeter should be provided; the voltmeter should have proper scales of measurement.
LECTRICAL CONNECTIONS
The electric signal of the probes is measured at the ends of the resistance
which short-circuits the terminals of the photodiode. The photocurrent
generated by the photodiode struck by the light is converted into a difference
in potential. The wiring diagram is shown in the following figure.
To obtain a reading precision of 1% of the difference in potential
at the ends of the resistance, the probe must be connected to a digital
multimeter with input resistance > 100 kΩ
MEASUREMENT
The probe output must be read with a digital multimeter with internal
resistance > 100kΩ. Connect the probe to the reading instrument as shown in
the previous chapter.
Having measured the difference in potential (DDP) at the ends of the probe,
the pho-to-radiometric measurement is given by the formula:
E = DDP/S
where:
E is the illuminance (Klux) or irradiance (µW/cm2) or PAR µmol /(m2s)
according to the
probe used
DDP is the difference in potential expressed in mV measured by the
multimeter,
S is the calibration factor marked on the probe in mV/klux or µV/(µW/cm2)
or µV/(µmol/(m2s)), according to the probe used.
Note for LPUVA01, LPUVB01 and LPUVC01
At the moment no international agreement exist for the calibration of this kind of radiometer, so the calibration coefficient is dependent from the calibration procedure like reported in the following article:
“Source of Error in UV Radiation Measurements “, T. C. Larason, C. L. Cromer on “Journal of Reaserch of the National Institute of Standards and Technology” Vol. 106, Num. 4, 2001. (The article is free on the NIST’s WEB site at the following address : https://nvlpubs.nist.gov/nistpubs/jres/106/4/j64lar.pdf)
SAFETY INSTRUCTIONS
General safety instructions
The probes have been manufactured and tested in accordance with the safety
standard EN61010-1:2010 “Safety requirements for electrical equipment for
measurement, control and laboratory use” and has left the factory in perfect
safety technical conditions.
The probes proper operation and operating safety can be ensured only if all
standard safety measures, as well as the specific measures described in this
manual, are followed.
The probes proper operation and operating safety can be ensured only in the
climatic conditions specified in this manual.
Do not use the probes in places where there are:
- Corrosive or flammable gases.
- Direct vibrations or shocks to the instrument.
- High-intensity electromagnetic fields, static electricity.
User obligations
The probe operator shall follow the directives and regulations below that
refer to the treatment of dangerous materials:
- EEC directives on workplace safety.
- National law regulations on workplace safety.
- Accident prevention regulations.
ORDERING CODES
- LPPHOT01 Photometric probe for measuring ILLUMINANCE, CIE photopic filter, diffuser for cosine correction. Output in mVdc per klux, cable L=5 m.
- LPRAD01 Radiometric probe for measuring IRRADIANCE, diffuser for cosine correction. Output in μV / μWcm-2, cable L=5 m.
- LPPAR01 Radiometric probe for measuring PHOTONS FLOW (light flow in the field of photosynthesis of chlorophyll). Cosine correction. Output in μV/μmol m-2s-1, cable L=5 m.
- LPUVA01 Radiometric probe for measuring IRRADIANCE in the UVA (315…400 nm). Output in μV/μWcm-2, cable L=5 m.
- LPUVB01 Radiometric probe for measuring IRRADIANCE in the UVB (280…315 nm). Output in μV/μWcm-2, cable L=5 m.
- LPUVC01 Radiometric probe for measuring IRRADIANCE in the UVC (220…280 nm). Output in μV/μWcm-2, cable L=5 m.
- LPBL Base with levelling device.
DELTA OHM metrology laboratories LAT N° 124 are ISO/IEC 17025 accredited by ACCREDIA for Temperature, Humidity, Pressure, Photometry / Radiometry, Acous- tics and Air Velocity. They can supply calibration certificates for the accredited quantities.
References
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