Kipp&Zonen SHP1 Pyrheliometer - Manual (Page 25)

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Instruction Manual - SHP1 - Smart Pyrheliometer
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SHP1 pyrheliometers only require suitable sources of power and radiation (light) to operate and make measurements. However,
it is necessary to connect them to some sort of readout or data storage device in order to save the measurements, there is no
internal data memory.
5.1 Data collection
An optimal setting for the data interval is to sample every second and store one minute averages. For setting up the combination
of pyrheliometer and data storage please refer to the manual of the data collection device.
Take care when using the analogue output to match the output range of the pyrheliometer closely to the input range of the data
collection device to maximise the available resolution and minimise noise.
This can be done by determining the maximum expected analogue output of the pyrheliometer in your application and taking
the minimum input range of your data collection device that can just handle that signal.
5.2 Key parts of SHP1 pyrheliometer
The detector of the SHP1 is based on passive thermal sensing element called a thermopile. Although the detector construction
differs between models, the fundamental working principle is applicable to all radiometers.
The thermopile responds to the total energy absorbed by a unique black surface coating developed by Kipp & Zonen, which is
non-spectrally selective. The thermopile warms up and the heat generated flows through a thermal resistance to a heat-sink, the
pyrheliometer housing. The temperature difference across the thermal resistance of the detector is converted into a small
voltage as a linear function of the absorbed irradiance.
A drying cartridge in the SHP1 pyrheliometer housing is filled with replaceable silica gel and prevents condensation on the inner
side of the window, which can cool down considerably on clear windless nights.
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5.2.1 Window
The material of the pyrheliometer window defines the spectral measurement range of the instrument. In general 99% of the
solar radiation spectrum will be transmitted through the window and will be absorbed by the detector. The SHP1 window is
made of quartz.
5. Operation and measurement
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The SHP1 pyrheliometer is delivered with a software programme SmartSensorDemo.exe, This software is supplied on a CD-ROM.
The operating computer must be running on a 32-bit or 64-bit version of Windows™ XP or Windows™ 7. Insert the CD into the
CD/DVD ROM drive of the operating computer and follow the on-screen installation instructions.
Note Before installing the software it is advised to disconnect all Modbus® devices except for the device that you wish
to configure.
The program is for testing the instrument and setting parameters. Basic data logging and display of data on a PC is also possible.
The software can handle up to 10 SHP pyrheliometers at the same time connected to the same RS-485 to USB converter. This
software is not intended for continuous long-term measurement, which should be done through the RS-485 network controller.
The setup depends on the used RS-485 adapter. An interface that could be used is from B&B, model USOPTL4, that has galvanic
isolation between in- and output. One side holds the USB connector to the PC the other side has a connector for connection of
the wires. This RS-485 adapter is powered from its USB interface.
A power supply for the SHP1 is required, this can be from a 5 to 30 Volt. 12 VDC is advised.
For set-up the following connection to a PC can be used. It is advised to use a RS-485 interface with galvanic isolation between
PC and RS-485.
Care has to be taken when connecting to an ungrounded (portable) PC, especially when also the analogue output is used. The
mains filter inside the PC can generate huge voltage peaks that can exceed the limits of the SHP1 pyrheliometer.
4.1 Set up communication
When the Smart Sensor Demo program is opened there are 3 basic functions available; ‘Overview’, ‘Instrument’ and ‘Chart’.
With the ‘Overview’ tab active the communication parameters can be set as follows:
1. Select the communication port where the RS-485 converter is connected
2. Set the baud rate (19200 is the default setting)
3. Set the number of data bits and parity (8 bits with even parity is the default setting)
4. Set the sampling time (1 poll per second is the default setting)
5. Press the button ‘Discover the first connected device’ (or press ‘Discover all connected devices’ if there is more than one
device connected)
4.2 Change the Modbus® address
With the ‘Overview’ tab active, you have the possibility to change the Modbus® address.
The default Modbus® address of a SHP1 pyrheliometer is 1. Before you can use the instrument in your network you must reconfigure
the address to a unique number. Each Modbus® device connected to a network must have a unique address.
1. Enter the old Modbus® address, this can be found with the button ‘Discover all connected devices’ (for example, enter 1).
2. Enter the new Modbus® address. This must be a unique number (for example, 24).
3. Press the ‘Change Modbus address’ button.
When the address has been changed the SHP1 pyrheliometer will restart itself.
4.3 Instrument data
With the ‘Instrument’ tab active the connected SHP1 pyrheliometer measurements are displayed. If multiple SHP1’s are connect-
ed the display will show alternating values from the different instruments. The large display showing the radiation can be
changed to (Body) Temperature.
The Body Temperature, SHP1 Power Supply Voltage and Time since power on are displayed in the lower part of the screen.
4.4 Chart
With the Chart’ tab active the SHP1 pyrheliometer measurements can be displayed as a graph.
It will show the last 250 measurements of irradiance (‘Radiation’ in W/m²) and/or the pyrheliometer housing temperature
(‘Body Temp’ in °C), as an accumulating graph. Vertical scaling can be set to maximum or automatic.
4.5 Data logging
Under File in Smart Sensor Demo the data logging can be set. The data format options are txt or csv. The csv log file has the
following format:
Together with the Modbus® address and the radiation data the body temperature and the power supply voltage to the SHP1
pyrheliometer are recorded.
At the bottom of the Smart Sensor Demo screen the message ‘The logfile C:\SHPdata\SHP-00.csv is open, press F12 to Append
Data.’ can be shown. With F12 a new data set can be linked to an existing file. Below is an example of a .txt file with linked data
from 2 days.
[11-1-2012 11:08:14]
DATE;TIME;SLAVE;SERIALNR;RADIANCE W/m²;TEMP C;POWER V
2012-01-11;11:08:15;001;00-0005; 708;30.7; 5.0;
2012-01-11;11:08:16;001;00-0005; 708;30.7; 5.0;
2012-01-11;11:08:17;001;00-0005; 708;30.7; 5.0;
[12-1-2012 9:20:17]
DATE;TIME;SLAVE;SERIALNR;RADIANCE W/m²;TEMP C;POWER V
2012-01-12;09:20:30;001;00-0005; 928;22.8; 5.0;
2012-01-12;09:20:37;001;00-0005; 929;22.8; 5.0;
2012-01-12;09:20:38;001;00-0005; 929;22.8; 5.0;
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5.2.2 Detector
The thermopile sensing element is made up of a large number of thermocouple junction pairs connected electrically in series.
The absorption of thermal radiation by one of the thermocouple junctions, called the active (or ‘hot’) junction, increases its
temperature. The differential temperature between the active junction and a reference (‘cold’) junction kept at a fixed temper-
ature produces an electromotive force directly proportional to the differential temperature created.
This is a thermoelectric effect. The sensitivity of a pyrheliometer depends on the individual physical properties of the thermopile
and its construction. The sensitivity of each thermopile is unique and therefore each radiometer has an individual calibration
factor. This sensitivity is stored in the SHP1 pyrheliometer configuration memory.
The unique black coating on the top surface of the thermopile has a rough structure that effectively ‘traps’ more than 97 % of the
incident radiation and heats up the hot junctions. The black-coated thermopile forms the detector, which has a spectral selectivity
of less than 2 %. This means that within the spectral range of the pyrheliometer, the absorption for each wavelength is equal to
within 2 %. The black absorptive coating is one of the most crucial and delicate parts of the pyrheliometer, Kipp & Zonen’s
provides the best possible stability over a long period of time under all meteorological circumstances.
5.2.3 Housing
The radiometer housing accommodates all the key parts of a SHP1 pyrheliometer. The anodized aluminium parts are lightweight
and give high mechanical and thermal stability to the instrument.
Due to fine mechanical construction SHP1 pyrheliometers are virtually sealed and comply with international standard IP 67.
5.2.4 Drying cartridge
To keep the detector and electronics dry and to prevent condensation forming inside the window with temperature changes a
self-indicating silica gel desiccant is used to absorb humidity within the pyrheliometer. When fresh the desiccant has an orange
colour. After some time absorbing moisture the colour will change to clear (transparent). At this time the silica gel is not fully
saturated, but should be replaced with fresh orange desiccant as soon as possible. Replacement desiccant is available through
Kipp & Zonen representatives.
5.2.5 Cable and connector
For ease of installation and replacement during re-calibration of the radiometer, the SHP1 is provided with a waterproof cable
socket fitted to the pyrheliometer housing. The matching waterproof plug is normally supplied pre-wired to a very high quality
yellow cable selected for low noise, very wide temperature range and UV resistance.
Cables come pre-wired to the connector plug in a range of lengths, 10 m is standard. 25 m, 50 m and 100 m lengths are also
available. The connector plug can also be supplied loose for the user to fit to their own cable.
housing
detector aperture rings rain shield
alignment aids drying cartridge quartz window
connector
smart interface