AT BF5 User manual

User Manual for the
Sunshine Sensor
type BF5
Delta-T Devices Ltd
BF5-UM-2.3

Notices
Copyright
All rights reserved. Under the copyright laws, this manual may not be
copied, in whole or in part, without the written consent of Delta-T Devices
Ltd. Under the law, copying includes translation into another language.
Copyright © 2022 Delta-T Devices Limited
BF5 Sunshine Sensor optics design and theory are Copyright © 1996
John Wood, Peak Design & Development, Winster, Derbyshire, U.K. and
protected by Patent Nos. EP1012633 & US6417500.
Trademarks
Windows is a registered trademark of Microsoft Corporation.
All other trademarks are acknowledged. Some names referred to are
registered trademarks.
CE Conformity
The BF5 Sunshine Sensor conforms to EU regulations regarding
electromagnetic emissions and susceptibility and is CE marked by
Delta-T Devices Ltd.
For certificates look on our website at www.delta-t.co.uk ,
or the Delta-T Software and Manual DVD.
Warnings
To maintain conformance to CE standards, the equipment must be used
as described in this manual. Modifications to the equipment may invalidate
CE certifications.
Delta-T Devices Ltd reserves the right to change the designs and
specifications of its products at any time without prior notice.
Authors
John Wood, Edmund Potter, Stephen Nobbs, Nick Webb.
User Manual Version: 2.3 Jul 2022
Delta-T Devices Ltd Tel: [phone]
130 Low Road, Burwell Fax: [phone]
CAMBRIDGE CB25 0EJ e-mail: [e-mail]
U.K. www: http://www.delta-t.co.uk

BF5 User Manual v 2.3 Contents  3
Contents
1
Notices 2
Introduction 6
About this Manual 6
Description and Functions 6
What it measures 6
What it is used for 7
Advantages of BF5 7
SunRead software 7
Use with a data logger 7
Use with SunScan 8
Differences from BF1, BF2 and BF3 8
Construction 9
Heater 9
Accessories 11
Mounting 11
Cables 11
Power Considerations 12
Heater 13
Getting Started 15
PC software 15
SunRead Installation 15
Connect your BF5 16
Preliminary Checks 17
Battery and Desiccant 17
Check the Dome 17
Use with SunScan 18
Setting up the BF5 18
Connecting to SunScan 18
Environment and Moisture protection 19
Use with a data logger 20
Effect of engineering units on sensitivity and resolution 20
Sunshine Status Output 20
Analogue outputs 21
Simplified output schematic 22
Suggested power supply connections 23

4  Contents BF5 User Manual v 2.3
Suggested Sun output connections 25
Ground and screen connections 27
Delta-T data logger connections 28
GP1 logger 28
GP2 Logger 28
DL2e logger 28
DL6 logger 28
Technical reference 29
Specifications 29
BF5 Accuracy and Resolution 29
Other specifications 30
BF5 Components Specifications 31
BF5 - SunScan Cable 31
BF5 Logger Cable 31
BF5 Analogue Extension Cables Can be used to extend both
BF5-Sunscan cable and BF5-Logger Cables 31
RS232 Serial Cable 31
Serial Extension Cable 32
Telescopic Tripod 32
Cross Arm for Mast Mount 32
Cosine response 33
Spectral response 34
Routine Maintenance 35
Batteries 35
Desiccant 35
Maintaining the dome 35
Recalibration of BF5 35
Warranty and Service 38
Terms and Conditions of Sale 38
Service and Spares 39
Technical Support 39
Contact details: 39
Problems 40
Problem Reports 40
Troubleshooting 40
BF5 Not Responding 40
Appendix A: Design and Test Summary 41
Introduction 41
Design objectives 41
How the design evolved 41
Calculation of Outputs 42
Conversion to appropriate units 42

BF5 User Manual v 2.3 Contents  5
Molar units (mol.m-2.s-1) 42
Energy units (W.m-2) 42
Illuminance units (lux) 43
Sunshine state 43
Glossary 48
Index 49

6  Introduction BF5 User Manual v 2.3
Introduction
About this Manual
This manual describes the BF5 Sunshine Sensor, and how to use it.
SunScan Users: If using the BF5 with the SunScan Canopy Analysis
system refer to the Preliminary Checks on page 17 and Use with
SunScan on page 18.
See also the SunScan documents on the Software and Manuals DVD.
Appendix 1 describes the BF5 design and includes a summary of the test
results of several experimental trials of its predecessors, the BF3 & BF2.
See also:
BF5 Quick Start Guide
BF3 Optical Design v2
BF3 Evaluation
These are also on the Software and Manuals DVD.
Description and Functions
What it measures
 The BF5 Sunshine Sensor is one sensor with three output channels:-
1. Total (global) solar radiation
2. Diffuse radiation
3. Sunshine status.
 The Direct beam component of solar radiation can be calculated from
the Total minus the Diffuse component.
 You can set up the two radiation outputs to give millivolt signals
scaled to the radiation units of your choice:
For PAR, in mol.m-2.s-1
For Energy, in W.m-2 ,or
For Illuminance, in klux .
The Sunshine status output is a logic level that corresponds to
sun, or no sun. This can be processed to give sunshine hours
duration.
 The Sunshine status threshold corresponds to the World Meteorology
Office (WMO) value of 120 W.m-2 in the direct beam, using an

BF5 User Manual v 2.3 Introduction 7
algorithm based on the Total radiation, and the ratio of Total to
Diffuse radiation.
 The radiation outputs have a cosine-corrected response.
What it is used for
 SunScan Canopy Analysis System reference
 Canopy analysis studies, and HemiView reference information
 Meteorological Global Direct and Diffuse solar radiation and Sunshine
duration measurements
 Solar energy monitoring, and solar collector studies
 Architecture and building design, illumination and heat balance
studies of buildings
Advantages of BF5
 It requires no shadow band.
 There are no moving parts.
 It does not need to be adjusted or repositioned to track the sun – a
distinct advantage over devices with shadow rings.
 It does not need to be oriented towards North. It will work accurately
in any orientation as long as it is mounted horizontally.
 It does not require knowledge of the Latitude or Longitude, and can
be used at any Latitude or Longitude.
 It measures sunshine hours as well as Total and Diffuse radiation
 A heater allows use in condensing and frosty situations.
SunRead software
SunRead runs on a PC running Windows 10, 8, 7, Vista XP.
About SunRead
 Reads the BF5 output values and status information via the PC
RS232 serial port.
 Sets the BF5 output units, to mol.m-2.s-1 (PAR), or W.m-2 (Energy), or
klux (Illuminance) as required.
 Logs data directly to PC.
Use with a data logger
 The three outputs of the BF5 can be logged with a suitable data
logger. The Total and Diffuse radiation millivolt outputs require two
analogue channels. The use of a data logger with differential sensor
inputs (rather than single-ended) is recommended.

8  Introduction BF5 User Manual v 2.3
 The sunshine state logic output can be taken to a digital channel, or
for some purposes can be connected to an analogue channel in order
to give readings of sunshine duration.
 The BF5 is a powered sensor. For power economy, the BF5 can be
woken up via a warm-up signal from the data logger.
 The internal heater requires a separate power supply. This should be
completely isolated from all other BF5 ground connections.
Use with SunScan
 The SunScan system is used for measuring PAR (Photosynthetically
Active Radiation) interception by plant canopies, and hence
estimating Leaf Area Index (LAI).
 The BF5 can be connected to SunScan probe to provide an
instantaneous reference of solar radiation incident on the canopy.
The measurements give the incident Diffuse and Total PAR above
the canopy. This also improves the accuracy of estimating canopy
LAI.
Differences from BF1, BF2 and BF3
 The BF1 was a very simple sensor consisting of two PAR
photodiodes and an adjustable shadow band. It measured Total and
Diffuse PAR. It required alignment to true North, and the shadow
band required frequent adjustment.
 The BF2 design measured Total and Diffuse PAR without needing
any adjustment or North alignment, only horizontal levelling. The BF2
also measured Sunshine state.
 The BF3 used the same optical design as the BF2, but gave the user
a choice of output units for Total and Diffuse radiation, in mol m-2 s-1
(PAR) , Wm-2 (Energy) , or klux (Illuminance) , as well as Sunshine
state.
The BF5 has the same performance and specifications as the BF3, but
with an improved electronic and mechanical design.
 The power consumption is improved:- the external power requirement
reduced from 6.5 to 2 mA, the number of internal AA batteries
reduced from four to two, and their typical lifetime increased from 6 to
12 months.
 The accuracy of the analogue outputs has been improved, with the
output offset reduced to 3mV.
 There are now no internal jumpers or fuses.
 The design also includes a heater and more rugged and weather-
proof cabling connectors and extension cables which are now
interchangeable with the SPN1 Sunshine Pyranometer.

BF5 User Manual v 2.3 Introduction 9
Construction
Seven cosine-corrected photodiodes are arranged under a patterned,
hemispherical dome, along with a levelling bubble, a desiccant-status
indicator, and a red light emitting diode (LED). The LED flashes when the
photodiodes are powered up for a reading.
There are two panel mounted sockets for communications:
 An 8 pin, M12 male analogue socket for connection to SunScan or to
a data logger.
This can also connect to a logger warm-up power supply for the BF5
sensor and to a separate power supply for the heater.
 A 5-pin M12 male connector serial port for connection to a PC or to
the SunScan radio link option.
The serial port is provided for checking real time readings, for changing
the output units, and for logging data directly to the PC.
A camera tripod type connector (1/4” BSW thread) is fitted to the base.
Heater
The BF5 is fitted with a thermostatically controlled heater for protection
against frost and condensation. Its use is recommended for logging
applications. It requires a separate external 12V DC power supply.
Use of the heater stabilises the internal temperature of the BF5 in cold
conditions, keeping the dome free of frost and resulting in greater
measurement accuracy.
The heater consists of two 15W resistors fixed to the shadow-mask.
When power is applied to the heater it works as follows:-
 If the external temperature is above 5C, the heater provides 2W,
reducing to zero above 35C.
This is sufficient to remove condensation and dew.
 Whenever the temperature drops below 5C the heater is increased,
to full power below 0C - to remove snow or ice.
At zero wind speed a BF5 at minus 20C will become snow and ice free in
30 minutes once power is applied to the heater.
At 2m.s-1 wind speed the dome will remain snow and ice free down to
minus 10C.
Warning:The bare heaters can get hot enough to burn your skin when on.
Do not operate the heaters with the dome removed.
Warning: Ensure the heater ground is isolated from all other BF5 ground
connections. If possible use a data logger with differential sensor inputs.
See also page 21

10  Introduction BF5 User Manual v 2.3
Cable connectors and components inside the dome
Section through BF5, showing internal PCBs and battery pack

BF5 User Manual v 2.3 Introduction 11
Accessories
Mounting
Mount the BF5 to a camera tripod if using it close to, or above low field
canopies (i.e. up to about 1.8m. A standard camera tripod socket is
mounted in the base of the BF5 for this purpose (¼ inch Whitworth x
8mm).
Above this height the BF5-M (1m x 32mm) cross-arm adaptor may be
useful.
It includes a Manforotto type 482 camera adaptor and a KeeKlamp type
45-86 connector. This is compatible with the Delta-T M2 weather station
mast and with many building scaffolding systems.
Cables
Separate cables and extension cables are available for connecting the
BF5 to a PC, to SunScan and to a data logger, as shown in the diagram
above.
The logger cable can also be used to connect external power to the BF5
sensor (e.g logger warmup power) and, separately, to connect power to
the BF5 heater.
For full details see BF5 - SunScan Cable on page 31.
See also the BF5 Quick Start Guide.
RS232 cable
10 m
1.5 m
5-way
M12
female
5-way
M12
female
9-way
serial
female
5-way
M12
male
SP-BF-RS01
SP-BF-RS10
BF5 end
CABLE OPTIONS
RS232 extension
cable
5 m
10 m
25 m
8-way
M12
female
8-way
M12
male
EXT/8w-05, EXT/8w-10 and EXT/8w-25
BF5 to SunScan
cable or logger
extension cable
8-way
M12
female
Flying
leads SP-BF/w-05
Logger cable

12  Introduction BF5 User Manual v 2.3
Power Considerations
The BF5 is a powered sensor. There are four possible sources of power:
1. The internal 3V alkaline batteries, if fitted. These are optional.
2. Power from the data logger. This only needs to be applied when the
logger takes a reading. The BF5’s Total, Diffuse and Sun analogue
outputs are valid 100ms after power is applied, and are then updated
every 250ms. These analogue outputs are only enabled when there is
a voltage present on the data logger power input (via DL-Power).
3. Power from a 12V heater supply.

BF5 User Manual v 2.3 Introduction 13
4. Power from the PC’s serial port (but not some laptops). The BF5
draws power from the PC DTR signal. Most computer serial ports will
provide enough power for the BF5 sensor electronics (but not its
heater).
If more than one of these sources is present, then power is generally
taken from the source with the highest voltage.
If no alkaline batteries are fitted, the power supply must be capable of >5V
at 2mA.
To prevent power being drawn from the data logger include a 10k resistor
in the logger power cable. This is OK as long as power is available from
elsewhere, e.g. from the heater supply
See also the BF5 Quick Start Guide.
Heater
The BF5 is fitted with an internal thermostatically controlled heater for
protection against frost and condensation. The heater is mounted on the
shadow mask, which will transfer heat around the inside of the dome and
the top of the enclosure.
When power is applied to the heater supply cables, it works as follows:-
 The heater current is controlled by a 8 Hz pulse-width modulated
switch.
 If the external temperature is below 0C, the heater provides the full
power available (up to 20W at 15V).
 Above 0°C, the power reduces smoothly to 20% at 5C, and then
down to nothing at 33°C.
Heater control
0
10
20
30
40
50
60
70
80
90
100
-10 -5 0 5 10 15 20 25 30 35 40
Temp degC
Heater Current %

14  Introduction BF5 User Manual v 2.3
At zero wind speed the dome will remain snow and ice-free down to minus
20C.
At 2m.s-1 wind speed the dome will remain snow and ice-free down to
minus 10C.
In air temperatures below 5  C the heater can consume 1.5A at 12V DC so
a 40 Ah car battery will only last about one day. For extended data logging
in cold climates, we recommended that you power the heater via a 12V
DC output supply which is itself powered from the mains.
Warning! Do not apply AC mains power to the BF5.
Warning Ensure the heater ground is isolated from all other BF5 ground
connections.
If possible use a data logger with differential sensor inputs.
See also page 21

BF5 User Manual v 2.3 Getting Started  15
Getting Started
The BF5 is shipped with the internal alkaline batteries installed and
connected.
To check readings, record or log readings use either:
 a Windows PC running SunRead, or
 an external data logger fully programmed and wired up, or
 a SunScan system.
Each require their own special cable(s) - see page 11
See also BF5 Quick Start Guide
In the field you need something on which to mount the BF5 horizontally.
 Use a camera tripod, e.g. type BFT1, or
 Bolt onto a suitable horizontal surface using the four M4 bolt holes
in the base of the BF5 plastic housing, or
 Use the BF5-M cross arm. This is compatible with the Delta-T 2m
weather station mast and with many builder’s scaffolding
systems.
See also the BF5 Quick Start Guide.
PC software
The SunRead software runs under Microsoft Windows 98 or later, with a
free RS232 port or USB-Serial adapter.
SunRead Installation
You need SunRead version 1.5 (or later).
This is provided on the Software and Manuals DVD.
On most PCs, the CD will start automatically when inserted.
If it does not, run the file SETUP.EXE in the root folder
On the Contents Page scroll down to Software and click on Install
SunRead software
Follow the links to install the software.
Note also the SunRead Release Notes information in the ReadMe.txt file
on the DVD.

16  Getting Started BF5 User Manual v 2.3
Connect your BF5
Connect your BF5 to your PC using a cable SP-BF-RS01
Run SunRead. You will see the display screen below:
Serial port
The Serial port menu indicates which COM ports are available on the PC,
with a check mark for the one selected. Once a port is selected, it will be
interrogated periodically until a BF5 is found, then the version information
will be displayed, and power supply voltage and readings will be updated
every few seconds.
Status information, eg “not connected” or BF5
serial number
Selects from the
available serial
ports
Sets up data logging,
either to PC or built-in
logger (if fitted)
Software version
numbers
Firmware version
reported by BF5
Battery voltage if
batteries are fitted,
otherwise external
power supply
voltage
Total & Diffuse
readings, updated
every 2s. Icon
indicates sunshine
state.
Indicates BF5
output units.
Selecting different
units changes BF5
analogue output
scaling
Logging status, if
internal logger is
installed

BF5 User Manual v 2.3 Getting Started  17
Logging
This menu enables you to log readings directly to the PC.
About
The about box contains the software version, copyright statements, and
contact information for Delta-T. There is also a text summary of Date &
Time, BF5 version and units information, which can be copied onto the
clipboard, to be used where required. This assists the user to keep an
audit record.
SunRead will also work with BF2 and BF3 Sunshine sensors
Preliminary Checks
Battery and Desiccant
 Install the SunRead software on a PC, and connect the BF5 to the PC
RS232 serial port using BF5 serial cable type SP-BF-RS01.
The radiation measurements, units and battery voltage are displayed.
Ideally, this should read close to 3 Volts (3000mV).
If below 1.5 Volts then the batteries are nearly flat and should be
replaced. If the voltage is in between, use your judgement.
The battery voltage can also be measured with a voltmeter after
undoing the four retaining screws in the lid.
 If the BF5 temperature is likely to exceed 50C, you are advised to
replace the Alkaline batteries with 1.5V Lithium batteries. This is
because the capacity of Alkaline batteries is poor above 50C.
WARNING: Do not use 3.6V AA Lithium batteries in the internal battery
holder. Only use 1.5 V AA batteries. Delta-T can supply these.
 Check the indicator paper in the dome.
It should be blue. If pink, replace the internal bag of desiccant.
To renew the desiccant, see Page 35.
 When you first use the BF5 in the field, check that it is reading in the
right engineering units, and that the values seem reasonable.
Check the Dome
The BF5 dome must be clear and unmarked for accurate measurements.
It can be cleaned with soapy water, using a soft clean cloth or paper
tissue.
Warning: The dome is acrylic plastic and may be damaged solvents

18  Use with SunScan BF5 User Manual v 2.3
Use with SunScan
Setting up the BF5
The BF5 is simple to operate. Make sure the BF5 output units are set to
the PAR molar units (mol m-2 s-1) using SunRead.
As a general guide, the above-canopy reference measurements should be
made close to, or above, the position of the SunScan probe. Tall
canopies will undoubtedly exercise your ingenuity in achieving this!
Using the tripod
The BF5 has a camera tripod mounting screw socket in the base. This is
probably the most convenient mounting method to use above low field
canopies (up to about 1.8 m high). If you are working with canopies higher
than this, it may be convenient to use the cross arm mounting kit type
BF5-M which is compatible with the Delta-T Weather Station mast, and
with many building scaffolding systems - or devise your own.
Levelling
The BF5 is equipped with a miniature bubble level. The tripod supplied
type BFT1 has 3-axis adjustment to facilitate levelling. The sensor is level
when the bubble is within the central circle.
It is more important to level the BF5 accurately than the SunScan probe.
Connecting to SunScan
Options:
 Use cable type EXT/8w- 05 with optional extension cables type
EXT/8w-xx (where x = 5, 10 or 25m) to connect the BF5 directly into
the socket on the back of the SunScan Probe.
Or use the BF5-RL4 to SS1-RL4 Sunscan radio link
If you are just checking to see that the BF5 is working, or measuring Leaf
Area Index, it is OK to use the radio link.
 Place the SunScan next to the BF5
 Run the SunData program on the PDA and press Read.
The Incident and Transmitted radiation readings should then appear
on the SunData display.
 Check that the “Transmitted” (i.e. SunScan) and “Incident” (BF5)
readings are within 10% of each other.
(Note: 10% corresponds to a Leaf Area Index error of 0.1 – which is
normally an acceptable precision for LAI measurements)

BF5 User Manual v 2.3 Use with SunScan  19
Note: the radio link can be up 3 seconds behind – this could give
inaccurate readings in a turbulent atmosphere. So if using the BF5 to
calibrate SunScan it is better to use the cable EXT/8w-05 .
If SunScan and BF5 disagree by more than 10% it may be appropriate to
recalibrate the SunScan using the BF5 as a reference.
For further instructions, see the SunScan User Manual.
Recalibration of the BF5 itself in the field is not recommended.
Always fit the internal batteries when using the BF5 with SunScan, as
SunScan does not provide enough external power to operate the BF5
reliably
Environment and Moisture protection
Avoid putting the BF5, or any SunScan system components at risk when
working outdoors. Minimise, as far as practical, their exposure to high or
rapidly changing temperatures.
The BF5 is designed to resist dust and water jets (IP65), but is not
hermetically sealed. It will survive rainfall, but may not survive being
immersed in water.
Internal condensation will be avoided if you keep the desiccant fresh.
Inspect the desiccant indicator inside the dome. It should be blue.
The BF5 is reasonably robust, but does not have a drop test rating. Do not
drop it.

20  Use with a data logger BF5 User Manual v 2.3
Use with a data logger
The BF5 may be connected to an external data logger with readings being
taken continuously. The BF5 updates its output values four times per
second.
A logger with differential sensor inputs (rather than single-ended) is
recommended.
Diffuse and Total radiation {mol m-2 s-1 (PAR) , Wm-2 (Energy) , or klux
(Illuminance) } and Sunshine status outputs are available for logging.
Use cable type SP-BF/w05 to connect to a data logger.
This can be extended using cable type EXT/8w-xx (where x = 5, 10 or
25m) up to a maximum of 100 m.
Data is presented at the analogue and digital outputs of the logger cable
within 100 ms of power being applied via the Power + wire.
Where daytime temperatures fall below zero, or inaccuracies due to
condensation are undesirable, make provision to provide power to the
heater (via cable type SP-BF/w05).
The heater power supply must be isolated, not sharing any earth return
with the BF5 sensor outputs.
Effect of engineering units on sensitivity and
resolution
The choice of output units has an effect on output sensitivities, as shown
in the following table:
Output units Sensitivity Resolution Full scale
output
Molar
mol.m-2.s-1
1mV =
1 mol.m-2.s-1
0.6 mol.m-2.s-1 2500mV = 2500
mol.m-2.s-1
Energy
W.m-2
1mV =
0.5 W.m-2
0.3 W.m-2 2500mV = 1250
W.m-2
Illuminance
klux
1mV =
0.100 klux
0.060 klux 2000mV = 200
klux
Sunshine Status Output
The sunshine state output is a digital output, i.e. it has only two states, ON
and OFF. It uses a contact closure output (no sun = open circuit, sun =
short circuit).