LSI DPA252 Pyranometer Secondary Standard User Manual

Secondary Standard Pyranometer
DPA252
User’s manual

Revisions list

About this manual

The information contained in this manual may be changed without prior notification. No part of this manual may be reproduced, neither electronically nor mechanically, under any circumstance, without the prior written permission of LSI LASTEM.
LSI LASTEM reserves the right to carry out changes to this product without timely updating of this document. Copyright 2018-2019 LSI LASTEM. All rights reserved.

Introduction

The LSI LASTEM pyranometer is an instrument to measure the solar irradiance (direct and diffuse) which reaches the terrestrial surface.
With this instrument it is possible to measure not only the global radiation (see WMO n°8 7th ed.), but also the reflected sun radiation (albedometer) and the diffuse radiation by means of the occultation band.
The pyranometer measures radiation values within 300 and 3000 nm, with a visibility of 2 steradians. The element used to for the measurement is a thermopile whose external surface has been darkened with matt black paint bearing a reflecting power < than 2% (e>0.98) in the spectral area of the sensor.
The following table compares the specifications required for the pyranometers in “first class” or “second class” (ISO 9060) or in “good quality” (WMO n°8, 7th ed.) and the Lsi Lastem pyranometers.

ISO 9060| Secondary
standard| First
class| Lsi Lastem
1st class| Second
class| Lsi Lastem
2nd class
---|---|---|---|---|---
Response time (95 % response)| < 15 s| < 30 s| 26 s| < 60 s| 28 s
Zero offset:
(a)Response to 200 Wm’ net thermal radiation (ventilated)
(b)Response to 5 Kh-1 change in ambient temperature| 7 Wm-2
2 Wm-2| 15 Wm-2
4 Wm-2| 12 Wm-2
2 Wm-2| 30 Wm-2
8 Wm-2| 14 Wm-2
3 Wm-2
Stability (change per year, percentage of full scale)| 0,8 %| 1,5 %| < 1 %| 3%| <1,5 %
Non-linearity (percentage deviation from the responsivity at 500 Wm” due to any change of irradiance within the range 100 to 1000 Wm 2)| 0,5 %| 1%| 0,75%| 3%| 1,5 %
Directional response for beam radiation (the range of errors caused by assuming that the normal incidence responsivity is valid for all directions when measuring, from any direction, a beam radiation whose normal incidence irradiance is 1000 Wm”)| 10 Wm-2| 20 Wm-2| 20 Wm-2| 30 Wm-2| 30 Wm-2
Spectral sensitivity (percentage deviation of the product of spectral absorptance and spectral transmittance from the corresponding mean within the range 200 to 3000 nm)| 2%| 5%| < 2 %| 10%| < 2 %
Temperature response (percentage maximum error due to any change of ambient temperature within an interval of 50 K)| 2%| 4%| < 4 %| 8%| < 7 %
Tilt response (percentage deviation from the responsivity at 0° tilt (horizontal) due to change in tilt from 0° to 90° at 1000 Wm’)| 0,5 %| 2%| –| 5%|
WMO n°8 r ed. Pyranometer table 7.5|
Achievable uncertainty ( 95 % confidence level):
– Hourly totals
– Daily totals| 3%
2%| 8%
5%| < 8 %
< 5 %| 20%
10%| < 20 %
< 10 %

Technical features

WMO estimate on achievable accuracy
for daily sums| ±2%
Spectral range| 285÷3000 nm
Non-stability| <± 0,5% change per year
Directional response| <±10 W/m2
Tilt response| <± 0,2% (0÷90° at 1000 W/m2
Temperature response| <± 0,4% (-30÷50°C)
Zero offset a (response to 200 W/m2  net thermal radiation)| <5W/m2 (unventilated)
Zero offset b (response to 5K/h change
in ambient temperature)| <±2 W/m2
Non linearity| <± 0.2 % (100 to 1000 W/m2)
Stability (% change/year)| <± 0.5 %
Standard built-in temperature sensor| YES
Standard built-in heater| YES (12 Vdc, 1,5W)
Data provided with each sensor| • Calibration certificate
• Temperature dependence data
• Directional response data

Calibration Factor

Each pyranometer is supplied with a Calibration Report produced by comparison, under the sun or under a lamp (ISO 9847), with a pyranometer calibrated at the WRC-PMOD in Davos (WRC: World Radiation Center; PMOD: Phisikalisch Meteorologisches Observatorium Davos).
The Calibration Report contains the Calibration Factor with its expanded uncertainty. This Factor must be entered in the data logger. For LSI LASTEM’s data logger the Calibration factor is set using 3DOM software, in Measure Properties:

Product installation

The pyranometers must be exposed towards the equator in a place that, in every season, is free of shadows during the day and installed at a height of 2 m on grassy places.

General safety rules

Please read the following general safety rules in order to avoid injuries to people and prevent damages to the product or to possible other products connected with it. In order to avoid any damages, use this product exclusively according to the instructions herein contained.
The installation and maintenance procedures must be carried-out only by authorized and skilled service personnel.
Carry-out all connections in a suitable manner. Pay strict attention to the connection diagrams supplied with the instrument.

Mechanical installation

A pyranometer is sensitive to thermal shocks. Do not mount the instrument with the body in direct thermal contact to the mounting plate (so always use the levelling feet also if the mounting is not horizontal), do not mount the instrument on objects that become very hot (black coated metal plates). in case of horizontal mounting only use the bubble level and levelling feet. For inspection of the bubble level the sun screen must be removed. By convention with the cable exit pointing to the nearest pole (so the cable exit should point north in the northern hemisphere, south in the southern hemisphere).

Do the Installation on pole using a DYA049 collar and DYA034-035 support. Follow these steps:

1. Remove the radiant protective screen from the pyranometer body.

2. Fix the DYA032-034-035 support the DYA049 collar and mount them on pole.

3. Turn the support until the sensor points to the terrestrial equator.

4. N.2 x M5 bolt at 65 x 10-3 m centre to centre distance on north-south axis, connection from below under the bottom plate of the instrument. Or 1 x M6 bolt at the centre of the instrument, connection from below under the bottom plate of the instrument

5. Reassemble the protective screen on the pyranometer body.

Electrical connection

Connections must be performed following the drawing of the pyranometer:

Operation check

To check the sensor output it is necessary to have the accompanying drawing (DISACC) of the sensor, in the last page of this document, and a multimeter.
Check the electrical resistance of the sensor between the green (-) and white (+) wire. Use a multimeter at the 1000 range. Measure the sensor resistance first with one polarity, than reverse the polarity. Take the average value. The typical resistance of the wiring is 0.1 /m. Typical resistance should be the typical sensor resistance of 100 to 200 plus 1.5 for the total resistance of two wires (back and forth) of each 5 m. Infinite resistance indicates a broken circuit; zero or a low resistance indicates a short circuit. Check if the sensor reacts to light: put the multimeter at its most sensitive range of DC voltage measurement, typically the 100 x 10-3 VDC range or lower. Expose the sensor to strong light source, for instance a 100 W light bulb at 1 x 10-1 m distance. The signal should read > 2 x 10-3 V now. Darken the sensor either by putting something over it or switching off the light. The instrument voltage output should go down and within one minute approach 0 V. Check the data acquisition by applying a 1 x 10-6 V source to it in the 1 x 10-6 V range. Check the condition of the connectors (on chassis as well as the cable).

• Note that night-time signals may be negative (down to -5 W/m2 on clear windless nights), due to zero offset a.
• Check if the pyranometer has clean domes.
• Check the location of the pyranometer; are there any obstructions that could explain the measurement result.
• Check the orientation / levelling of the pyranometer.
• Check if the right calibration factor is entered into the algorithm. Please note that each sensor has its own individual calibration factor, as documented in its calibration certificate. Check if the voltage reading is divided by the calibration factor in review of the algorithm.
• Check the condition of the wiring at the logger.
• Check the cable condition looking for cable breaks.
• Check the condition of the connectors (on chassis as well as the cable).
• Check the range of the data logger; signal can be negative (this could be out of range) or the amplitude could be out of range. Check the data acquisition by applying a 1 x 10-6 V source to it in the 1 x 10-6 V range. Look at the output. Check if the output is as expected.
• Check the data acquisition by short circuiting the data acquisition input with a 100 resistor. Look at the output. Check if the output is close to 0 W/m2

Maintenance

| 1 week| Data analysis| compare measured data to maximum possible / maximum expected irradiance and to other measurements nearby (redundant instruments). Also historical seasonal records can be used as a source for expected values. Analyse night time signals. These signals may be negative (down to – 5 W/m2 on clear windless nights), due to zero offset a. In case of use with PV systems, compare daytime measurements to PV system output. Look for any patterns and events that deviate from what is normal or expected
---|---|---|---
2| 2 weeks| Cleaning| cleaning use a soft cloth to clean the dome of the instrument, persistent stains can be treated with soapy water or alcohol
3| 6 months| inspection| inspection inspect cable quality, inspect connectors, Inspect mounting position, inspect cable, clean instrument, clean cable, inspect levelling, change instrument tilt in case this is out of specification, inspect mounting connection, inspect interior of dome for condensation
4| 2 years| desiccant replacement| desiccant replacement (if applicable). Change in case the blue colour of the 40 % humidity indicator turns pink (indicating humidity), then replace desiccant. Coat the rubber of the cartridge with silicone grease or vaseline. Desiccant regeneration: heating in an oven at 70 °C for 1 to 2 hours. Humidity indicator regeneration: heating until blue at 70 °C
5| 2 years| recalibration| recalibration by side-by-side comparison to a higher
standard instrument indoors according to ISO 9847 or
outdoors according to 1509846
6| 2 years| lifetime assessment| judge if the instrument should be reliable for another 2 years, or If It should be replaced
7| 6 years| parts replacement| if applicable / necessary replace the parts that are most exposed to weathering; cable, connector, desiccant holder, sun screen
8| 6 years| Internal inspection| if applicable: open instrument and inspect / replace 0-rings; dry internal cavity around the circuit board

Calibration

It is not necessary to re-calibrate the instrument frequently. It is advisable to re-calibrate the instrument every 2 to 3 years in order to keep calibration uncertainty variations in the range of 2%.
Recalibration of field pyranometers is typically done by comparison in the field to a reference pyranometer. The applicable standard is ISO 9847 “International Standard- Solar Energy- calibration of field pyranometers by comparison to a reference pyranometer”. At LSI LASTEM an indoor calibration according to the same standard is used.
LSI LASTEM recommendation for re-calibration: if possible, perform calibration indoor by comparison to an identical reference instrument, under normal incidence conditions.
In case of field comparison; ISO recommends field calibration to a higher class pyranometer. LSI LASTEM suggests also allowing use of sensors of the same model and class, because intercomparisons of similar instruments have the advantage that they suffer from the same offsets. It is therefore just as good to compare to pyranometers of the same brand and type as to compare to an instrument of a higher class. ISO recommends to perform field calibration during several days; 2 to 3 days under cloudless conditions, 10 days under cloudy conditions. In general this is not achievable. In order to shorten the calibration process LSI LASTEM suggests to allow calibration at normal incidence, using hourly totals near solar noon.

Disposal

This product is a device with high electronic content. In accordance with the standards of environmental protection and collection, LSI LASTEM recommends handling the product as waste of electrical and electronic equipment (RAEE). For this reason, at the end of its life, the instrument must be kept apart from other wastes.
LSI LASTEM is liable for the compliance of the production, sales and disposal lines of this product, safeguarding the rights of the consumer. Unauthorized disposal of this product will be punished by the law.

How to contact LSI LASTEM

In case of problem contact the technical support of LSI LASTEM sending an e-mail to support@lsi-lastem.com, or compiling the technical support request module at www.lsi- lastem.com.

For further information refer to addresses and numbers below:

• Phone number : +39 02 95.414.1 (switchboard)
• Address: Via ex S.P. 161 ­ Dosso n. 9 – 20049 Settala Premenugo, Milano
• Web site: www.lsi-lastem.com
• Commercial service: info@lsi-lastem.com 
• After-sales service: support@lsi-lastem.com, Repairs: riparazioni@lsi-lastem.com

LSI LASTEM SRL
INSTUM_04453

Documents / Resources

| LSI DPA252 Pyranometer Secondary Standard [pdf] User Manual
DPA252 Pyranometer Secondary Standard, DPA252, Pyranometer Secondary Standard, Secondary Standard, Standard
---|---

References

• lastem.com
• Environmental Monitoring Solutions - LSI LASTEM
• Environmental Monitoring Solutions - LSI LASTEM
• Sign in to your account

Read User Manual Online (PDF format)

Read User Manual Online (PDF format)  >>

Download This Manual (PDF format)

Download this manual  >>