DAVIS Solar Radiation Sensor User manual

Product#7821,7823,6450
S
OLAR
R
ADIATION
S
ENSOR
S
TANDARD
, I
NDUSTRIAL
, &
V ANTAGE P RO VERSIONS
The Davis Solar Radiation Sensor is a precision instrument that detects radia-
tion at wavelengths of 300 to 1100 nanometers. The spectral response of the sil-
icon photodiode detector is a good match to the spectrum of solar irradiance.
Avoid touching the small white diffuser at the top of the sensor. Any skin oil
on this surface will degrade the sensitivity of the sensor. To remove any oil
present, clean the diffuser with a clean swab and ethyl (denatured) alcohol. Do
NOT use rubbing alcohol.
The sensor is made up of the following components:
✦
Shield
The outer shell shields the sensor body from thermal radiation and pro-
vides a path for convection cooling of the body, minimizing heating of
the sensor interior. It provides a cutoff ring for cosine response, a level
indicator, and fins to aid in aligning the sensor with the sun’s rays.
✦ Body
The body houses the following components:
✦
Diffuser
Welded to the body for a weather-tight seal. Provides excellent
cosine response.
✦
Detector
An hermetically-sealed silicon photodiode.
✦
Amplifier
The amplifier converts the detector current into a 0 to +2.5V signal.
✦
Cable
The standard version of the sensor includes an attached 40' (12 m)
standard cable. The industrial version includes a 16' (5 m) shielded
cable. The Vantage Pro version comes with a 3' (0.9 m) standard
cable.

Page2 SolarRadiationSensor
M
OUNTING
H
ARDWARE
Please make sure you have all components listed below before continuing.
✦
Shield
✦
Body with cable attached
✦
Mounting hardware
Enables installation and
leveling of the sensor.
✦
Three #6-32 x 1-1/2"
(38 mm) machine screws
✦
Three springs
✦
Three #6 flat washers
✦
Three #6 screw retainers
✦
Three #4 screw retainers
✦
Three wood screws
✦ One #8-32 x 3/4" (19 mm)
machine screw
✦
One #8-32 hex nut
✦
One #8 flat washer
✦
One 3/16" (5 mm) cable
clamp
T OOLS AND M ATERIALS N EEDED
You may need some of the following tools and materials in order to complete
your installation. Please be sure you have everything you need before beginning.
✦
Medium Phillips screwdriver
✦
Scissors
✦
Center punch or nail (if mounting on wood surface)
✦
Drill with 7/8" (22 mm) and #36 (2.7 mm) drill bits (if mounting on wood surface)
✦
Wire cutters and stripper (industrial version only)

Contents: Page3
C
ONTENTS
:
S
PECIFICATIONS ARE
A
VAILABLE
For detailed technical information on the solar radiation sensor, call Technical
Support [phone] to request a specification sheet, or download it from our
website:
http://www.davisnet.com/support/weather/
S
TANDARD AND
I
NDUSTRIAL
V
ERSIONS
: I
NSTALLATION
Testing the Sensor
1. Attach the sensor cable to the connector S5 on the sensor interface module, or “SIM”.
Consult the System Installation manual for instructions
2. Press the appropriate key to make sure you are getting a solar radiation reading on
the console.
Consult the station manual for instructions on displaying solar radiation.
3. Shade the sensor and make sure the reading changes.
Standard and Industrial Versions: Installation.............................. 3
Testing the Sensor.......................................................................... 3
Installing the Sensor....................................................................... 4
Typical Standard Installation......................................................... 4
Typical Industrial Installation........................................................ 5
Mounting on the Sensor Mounting Arm......................................... 6
Mounting on the Sensor Tilting Bracket........................................ 7
Mounting on a Wood Surface.......................................................... 10
Routing Sensor Cable..................................................................... 11
Vantage Pro Version: Installation on the Sensor Mounting Shelf.. 12
Testing the Sensor.......................................................................... 12
Accessing the SIM........................................................................... 12
Securing the Sensor on the Shelf.................................................... 13
Routing Sensor Cable..................................................................... 14
If You Are Going to Install the Solar Radiation Sensor................. 15
Maintaining the Sensor.................................................................. 15
Technical Support.......................................................................... 16

Page4 SolarRadiationSensor
Installing the Sensor
Follow the instructions in this section to install your sensor. Before you begin, con-
sult the System Installation manual for instructions on labeling the sensor cable.
✦
For evapotranspiration (ET) or scientific measurements, the sensor can be
mounted on the Sensor Mounting Arm (SMA) or any level surface.
✦
For measurements where the immediate effect on humans is of interest, we recommend
that you mount the sensor such that its axis is aligned with the sun’s rays at solar noon.
This will maximize the mid-day readings and provide what is probably
a more accurate measure of the solar radiation people are exposed to.
The Health EnviroMonitor™ calculation of the solar radiation contribu-
tion to apparent temperature assumes that the sensor is tilted. The Sen-
sor Tilting Bracket #7706 is designed for this purpose.
✦ Similarly, if you wish to predict or monitor the irradiance on a solar voltaic or
thermal collection panel the data are probably most relevant if the sensor is tilted
to the same angle as the collection panel.
The Sensor Tilting Bracket #7706 is designed for this purpose.
Typical Standard Installation
The illustration below shows typical standard solar radiation installation. The
sensor cable attaches to connector S5 on the sensor interface module (SIM).
T
YPICAL
S
TANDARD
I
NSTALLATION

StandardandIndustrialVersions:Installation Page5
Typical Industrial Installation
The illustration below shows typical industrial solar radiation installation. The
sensor cable attaches to connector S5 on the sensor interface module (SIM).
T
YPICAL
I
NDUSTRIAL
I
NSTALLATION

Page6 SolarRadiationSensor
Mounting the Sensor on the Sensor Mounting Arm
Follow the instructions below to mount the sensor on the Sensor Mounting
Arm (SMA).
1. Route the cable through the large hole in the mounting arm if desired.
2. Place the shield onto the body as shown below.
P LACING S HIELD ONTO B ODY
3. Place a flat washer over the end of each screw and insert it into the body.
4. Place a spring over the end of each screw and hold the springs in place using a #6
screw retainer.
5. Secure the sensor to the mounting arm by driving the screws into the appropriate
holes as shown below.
M OUNTING THE S OLAR R ADIATION S ENSOR ON THE SMA
6. Using the bubble level on the sensor as a guide, adjust the sensor until it is level by
tightening or loosening the levelling screws as necessary.

StandardandIndustrialVersions:Installation Page7
7. Secure the sensor cable to the underside of the mounting arm using the 3/16" cable
clamp, #8-32 x 3/4" screw, #8 hex nut, and #8 flat washer as shown below.
S
ECURING
S
ENSOR
C
ABLE
Mounting the Sensor on the Sensor Tilting Bracket
Follow the instructions below to mount the sensor on the Sensor Tilting
Bracket. Do not install the bracket onto the mounting arm until instructed to do
so below.
1. Route the cable through the large hole in the bracket if desired.
2. Place the shield onto the body as shown below.
P
LACING
S
HIELD ONTO
B
ODY

Page8 SolarRadiationSensor
3. Place a flat washer over the end of each screw and insert it into the body.
4. Place a spring over the end of each screw and hold the springs in place using a #6
screw retainer.
5. Secure the sensor to the bracket by driving the screws into the appropriate holes as
shown below.
If mounting the sensor on the tilting bracket in a location under 46˚ latitude
or in a situation which requires the angle of the tilting bracket to be less than
28˚, you will need to use the standoffs supplied with the tilting bracket. Con-
sult the Sensor Tilting Bracket manual for details.
M OUNTING THE S OLAR R ADIATION S ENSOR ON THE S ENSOR T ILTING B RACKET
6. Position the Sensor Mounting Arm so it is pointed in the direction of the sun at solar
noon.
Solar noon occurs halfway between sunrise and sunset; consult your local paper
or the WeatherLink
®
software for sunrise and sunset times. To correctly align
the arm, screw a mounting screw part way into any of the sensor’s screw posi-
tions on the mounting arm and rotate the arm until the shadow from the screw
is parallel to the edge of the sensor arm at solar noon.
7. Attach the bracket to the mounting arm as described in the Sensor Tilting Bracket
instruction manual.
If you are installing both the solar radiation and the UV sensor on the sensor
tilting bracket, make sure you mount the solar radiation sensor on the sen-
sor tilting bracket before attaching to the sensor mounting arm.

StandardandIndustrialVersions:Installation Page9
8. If necessary, adjust the position of the sensor by tightening or loosening the levelling
screws.
When pointed directly at the sun, the shadows from the alignment fins
should appear as shown in the illustration below.
F
INAL SENSOR
P
OSITIONING
9. Secure the sensor cable to the underside of the mounting arm using the 3/16" cable
clamp, #8-32 x 3/4" screw, #8 hex nut, and #8 flat washer as shown below.
SECURING SENSOR CABLE

Page10 SolarRadiationSensor
Mounting the Sensor on a Wood Surface
Follow the instructions below to mount the sensor on a wood surface.
1. Using the template printed at the bottom of this page, mark the location of the neces-
sary pilot holes.
2. Using a drill with a #36 (2.7 mm) drill bit, drill pilot hole in the marked locations. If
necessary, bore a hole through the mounting surface using a 7/8" (22 mm) drill bit so
the bottom of the sensor can sit inside of it and the sensor cable can run to the other
side.
3. Route the sensor cable through the hole in the wood if desired.
4. Place the shield onto the body as shown below.
PLACING SHIELD ONTO BODY
5. Place a flat washer over the end of each screw and insert it into the body.
6. Place a spring over the end of each screw and hold the springs in place using a #4
screw retainer.
Use the template below to center-punch or mark pilot holes before drilling.
SOLAR RADIATION SENSOR MOUNTING HOLES TEMPLATE

StandardandIndustrialVersions:Installation Page11
7. Secure the sensor to the mounting surface by driving the screws into the appropriate
holes as shown below.
MOUNTING THE SOLAR RADIATION SENSOR ON AWOOD SURFACE
8. Using the bubble level on the sensor as a guide, adjust the sensor until it is level by
tightening or loosening the levelling screws as necessary.
9. Secure the sensor cable to the mounting surface. You may use the provided 3/16" cable
clamp, #8-32 x 3/4" screw, #8 hex nut, and #8 flat washer if possible.
Routing Sensor Cable
To prevent fraying or cutting of the
cable where it is exposed to
weather, secure it so it doesn’t
whip about in the wind. Use cable
clips or weather resistant cable ties
to secure the cable. Place clips or
ties approximately every 3 to 5 feet
(1 to 1.6 m). Do NOT use metal sta-
ples or a staple gun to secure
cables. Metal staples—especially
when installed with a staple gun—
have a tendency to cut the cables.
Note:Try not to tug on the cable in such a way as to loosen the connections between cables. Also,
make sure the sensor cable is not so taut that connections loosen or pull free due to the
strain. Many sensor problems occur because cable connections come loose.
Cable Clip Cable Tie

Page12 SolarRadiationSensor
VANTAGE PRO VERSION: INSTALLATION ON THE SENSOR MOUNTING SHELF
Follow these instructions to mount the solar radiation sensor on the shelf. The
shelf has two large holes, to hold a solar radiation sensor and a UV sensor. It
doesn’t matter which hole you use first.
Testing the Sensor
On Vantage Pro’s Integrated Sensor Suite (ISS), the sensor interface module, or
SIM, is inside the radiation shield. (The SIM is where the sensors connect with
the rest of the weather station). You need to remove the radiation shield plates
to access the SIM and test the sensor. Take your console with you.
On the rain collector side of your ISS, underneath the white mounting base is
the radiation shield. It consists of several white plastic plates.
Accessing the SIM
1. Remove the wing nuts, lock
washers and flat washers.
2. Remove the first three plates
of the radiation shield.
You should now be able to
see the SIM.
3. Plugthesolarradiationsensor
cable into the receptacle
labeled “SOLAR”on the SIM.
Hold the sensor body with
white diffuser pointed
upward. Do NOT touch
the diffuser. If you do,
clean it after mounting.
(See “Maintaining the Sen-
sor” on page 15.)
4. On your console, press the
“SOLAR”key to see reading.
Shade the sensor with your
hand — the value should
drop.
5. Unplug the sensor cable from
the SIM.
Do not put the shield plates
back on yet. You’ll have to
plug the sensor cable into the
SIM again, once you have
mounted the sensor.
Open Plate
Open Plate
Closed Plate
#8 Wing Nut
#8 Lock Washer
#8 Flat Washer
Antenna
deployment
hole (used on
Wireless only)
Sensor
Interface
Module
(SIM)
Mounting Base

VantageProVersion:InstallationontheSensorMountingShelf Page13
Securing the Sensor on the Shelf
1. Remove the rain collector cone: turn it
counter-clockwise until the latches
allow you to lift it up and off.
2. Place the shield onto the body as
shown.
3. Route the sensor cable down through
one of the large holes in the mounting
shelf.
4. Place a flat washer over the end
of each screw and insert it into
the body.
5. Place a spring over the end of
each screw and hold the springs
in place using a #6 screw
retainer.
6. Secure the sensor to the mount-
ing shelf by driving the screws
into the appropriate holes as
shown.
7. Using the bubble level on the sen-
sor as a guide, adjust the sensor
until it is level by tightening or
loosening the screws as neces-
sary.
Note:Final leveling of the sensor(s) should be done with the ISS mounted in its operating location.

Page14 SolarRadiationSensor
Routing the Sensor Cable
You will route the sensor cable through the base of the rain collector and out
through a hole, then connect it to the SIM inside the radiation shield. (This step
requires that the radiation shield is open. If it is not, remove the shield plates
now as shown in “Accessing the SIM” on page 12.)
See the illustration below as you follow these instructions.
1. Tie the sensor cable to the shelf support tube.
Use one of the plastic 4" cable ties provided with the sensor mounting shelf
to keep the cable in place. (#1 in illustration.)
2. Squeeze the cable down into the cable notch on the circular edge of the rain collector
base. The cable needs to be wedged down into the notch so it will come up inside the
rain collector cone when the cone is put back on.
3. Route the cable down and out through the hole in the base.
Plug the cable into the receptacle labeled “SOLAR” in the SIM, to see how
much slack will be left in the cable as you secure it inside the rain collector.
4. In the rain collector base, loop up the slack in the cable. Using the two cable clamps in
the base, secure one loop.
Tie the remaining loops of cable together with cable ties #2 & 3 as shown.
When securing the
sensor cable(s)
inside the rain col-
lector base, the goal
is to ensure that
the cables do not
interfere with the
tipping bucket
mechanism of the
rain collector.
Cable Tie #1
Cable Tie #2
Cable Tie #3
Cable Notch
Cable Clamps
NOTE: Route sensor cable(s) out through this hole
Tipping Bucket

MaintainingtheSensor Page15
5. Cut off the ends of the cable ties.
6. Put the rain collector cone back on the base, turning it clockwise until the latches
hold it in place. Be sure that it does not squeeze the sensor cable where it goes down
into the notch and up inside the cone.
Don’t put the cone back on if you’re going to install the UV sensor at this
time.
7. Clean the sensor as instructed in “Maintaining the Sensor”on page 15.
If You Are Going to Install the UV Sensor
If you’re installing the UV sensor also, use the same testing and installation
procedure just completed for the solar radiation sensor. In the rain collector
base, the cable clamps have room to secure one loop of the UV sensor cable and
one loop of the solar radiation sensor cable.
Reassembling Radiation Shield
Consult the illustration on page 12.
1. Slide the two open plates over the threaded studs.
2. Slide the single closed plate over the threaded studs.
3. Place a flat washer, lock washer and wing nut over one of the studs.
Tip: temporarily place a wing nut on one of the studs to hold the plates as
you place washers and a wing nut on another stud.
4. Finger-tighten the wing nut.
5. Repeat #3. and #4. until all three wing nuts are secure.
MAINTAINING THE SENSOR
For the most accurate readings, clean the diffuser after mounting, and then
periodically. Use ethyl alcohol (NOT rubbing alcohol) or water with a little
detergent in it.
Due to the sensitivity of solar radiation sensors it is common practice for man-
ufacturers to recommend re-calibration after a period of time. Here at Davis
Instruments we have seen approximately 2% drift per year on the readings
from these sensors. For applications demanding higher accuracy, the sensors
should be calibrated once every year.
Contact Technical Support [phone] about returning your sensor for cali-
bration.

Product Numbers: 7821, 7823, 6450
Davis Instruments Part Number: 7395.092
Solar Radiation Sensor, Standard, Industrial & Vantage Pro versions
Rev. C Manual (1/12/01)
This product complies with the essential protection requirements of the EC EMC
Directive 89/336/EC.
Copyright ©2000 Davis Instruments Corp. All rights reserved.
TECHNICAL SUPPORT
Before calling Technical Support [phone] regarding a problem with your
sensor, carefully check all cable connections from the sensor to the console.
Cable connections account for a large portion of the potential problems. Con-
nections should be firmly seated in the jacks and plugged in straight. If you
think a connection may be faulty, try jiggling the cable while looking at the dis-
play. If a reading appears intermittently on the display as you jiggle the cable,
the connection is faulty.