Vaisala FD12P User Manual
Weather Sensor
FD12P
USER'S GUIDE
M210296en-A
May 2002
PUBLISHED BY
Vaisala Oyj Phone (int.): +358 9 8949 1
P.O. Box 26 Fax: +358 9 8949 2227
FIN-00421 Helsinki
Finland
Visit our Internet pages at http://www.vaisala.com/
© Vaisala 2002
No part of this manual may be reproduced in any form or by any means,
electronic or mechanical (including photocopying), nor may its contents be
communicated to a third party without prior written permission of the copyright
holder.
The contents are subject to change without prior notice.
Please observe that this manual does not create any legally binding obligations for
Vaisala towards the customer or end user. All legally binding commitments and
agreements are included exclusively in the applicable supply contract or
Conditions of Sale.
_________________________________________________________________________________
Table of Contents
CHAPTER 1
GENERAL INFORMATION ..........................................................................11
About This Manual..................................................................11
Contents of This Manual......................................................11
Version Information................................................................12
Related Manuals .....................................................................12
Safety .......................................................................................12
General Safety Considerations............................................12
Product Related Safety Precautions ...................................13
Safety Summary ............................................................. 13
Ground the Equipment ...................................................13
Radio Frequency Interference Statement (USA) ...........15
ESD Protection .................................................................... 15
Trademarks .............................................................................16
Warranty ..................................................................................16
CHAPTER 2
PRODUCT OVERVIEW ................................................................................ 17
Introduction.............................................................................17
Hardware Structure .............................................................17
Sensing Elements ..........................................................19
Electronics Enclosure .....................................................20
Structural Elements ........................................................ 20
Operating Principle ..............................................................21
Using FD12P .......................................................................22
Equipment Nomenclature ......................................................23
Specifications .........................................................................24
Mechanical Specifications ...................................................24
Electrical Specifications.......................................................24
Optical Specifications ..........................................................25
Capabilities and Limitations ..................................................26
Visibility Measurement Specifications .................................26
Weather Sensing Specifications..........................................26
Environmental Specifications ..............................................27
CHAPTER 3
INSTALLATION ............................................................................................ 29
Organizing Installation ...........................................................29
Location and Orientation .......................................................30
Grounding and Lightning Protection....................................32
Equipment Grounding..........................................................32
Internal Grounding ............................................................... 34
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Grounding for Testing Purposes......................................... 34
Grounding Remote Units and Communication Cable......... 34
Cable Selection ...................................................................... 35
Line Power Cabling............................................................. 35
Communication Cable......................................................... 35
Unloading and Unpacking..................................................... 36
Unpacking Procedure ......................................................... 36
Storage Information ............................................................ 36
Installation Procedures ......................................................... 37
Constructing the Foundation............................................... 37
Mounting When Casting the Pad................................... 38
Mounting to an Existing Surface.................................... 38
Assembling the FD12P ....................................................... 40
Attaching the DTS14B Temperature Sensor to the Mast ... 41
Connecting Cables.............................................................. 43
Basic Wiring ................................................................... 43
Communication Cable EMC-shielding........................... 46
Connecting a Background Luminance Sensor or a
Day/Night Switch to FD12P ........................................... 48
Communication Options ..................................................... 50
Serial Communications Settings.................................... 50
Serial Transmission RS-232.......................................... 50
Serial Multipoint Transmission RS-485 ......................... 51
Modem DMX21 .............................................................. 52
Indicators and Manual Controls..................................... 54
Indicators .................................................................. 54
Manual Controls ....................................................... 54
Analog Transmission ..................................................... 55
Connecting the Maintenance Terminal.......................... 55
Startup Testing.................................................................... 56
Initial Settings...................................................................... 56
CHAPTER 4
OPERATION ................................................................................................ 59
Introduction ............................................................................ 59
User Commands in Normal Operation................................. 59
Markings Used in This Manual ............................................. 61
Entering/Exiting the Command Mode .................................. 61
OPEN Command ................................................................ 61
CLOSE Command .............................................................. 62
Automatic Message Sending ................................................ 62
Message Types................................................................... 63
Message 0 ..................................................................... 64
Message 1 ..................................................................... 64
Message 2 ..................................................................... 65
Message 3 ..................................................................... 65
Message 4 ..................................................................... 66
Messages 5 and 6 ......................................................... 66
Message 7 ..................................................................... 68
Message Polling ..................................................................... 69
FD12P Command Set............................................................. 70
HELP Command ................................................................. 70
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MES Command ...................................................................71
AMES Command............................................................71
Weather Related Commands ..............................................73
WPAR Command ........................................................... 73
WSET Command ...........................................................73
Precipitation Limit......................................................74
Weather Update Delay..............................................74
Haze Limit .................................................................74
Rain Intensity Scale................................................... 75
Violent Rain Limit ......................................................75
Heavy Rain Limit .......................................................75
Light Rain Limit.......................................................... 75
Drizzle Limit...............................................................75
Heavy Drizzle Limit....................................................76
Light Drizzle Limit ......................................................76
Snow Limit.................................................................76
Heavy Snow Limit......................................................76
Light Snow Limit ........................................................76
Snow Pellets Limit .....................................................77
Snow Grains Limit .....................................................77
Ice Crystals Limit .......................................................77
Hail Limit.................................................................... 77
DRD Scale................................................................. 77
Warm Limit ................................................................77
PRW Command..............................................................77
CLRS Command ............................................................78
WHIS Command.............................................................78
System Configuration Commands....................................... 79
PAR Command............................................................... 79
CONF Command............................................................80
BAUD Command ............................................................84
BLSC Command.............................................................84
Maintenance Commands..................................................... 85
STA Command ...............................................................85
CAL Command ...............................................................87
TCAL Command.............................................................87
CLEAN Command .......................................................... 88
CHEC Command............................................................89
FREQ Command ............................................................ 89
DRY and WET Commands ............................................89
AN Command .................................................................90
Analog Output Commands ..................................................91
Analog Output Calibration ..............................................91
Data Scaling ................................................................... 92
Hardware Check.............................................................92
Other Commands ................................................................93
TIME Command .............................................................93
DATE Command ............................................................93
RESET Command .......................................................... 94
CHAPTER 5
FUNCTIONAL DESCRIPTION .....................................................................95
General.....................................................................................95
Optical Measurement .............................................................96
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Optical Arrangement ........................................................... 96
FDT12B Transmitter Unit .................................................... 96
FDR12 Receiver Unit .......................................................... 98
Additional Measurements ..................................................... 99
General ............................................................................... 99
DRI21 Interface Board ........................................................ 99
DRD12 Rain Detector ....................................................... 100
DTS14B Temperature Sensor .......................................... 101
FDP12 Control Unit .............................................................. 101
Measurement Signal Processing........................................ 103
Optical Signal Processing................................................. 103
DRD12 Signal Processing ................................................ 104
Algorithm Description ......................................................... 105
Visibility ............................................................................. 105
Detecting Precipitation ...................................................... 106
Precipitation Intensity........................................................ 106
Precipitation Accumulation ............................................... 107
Present Weather ............................................................... 108
Precipitation Types ...................................................... 108
Liquid Precipitation ................................................. 109
Frozen Precipitation................................................ 110
Mixed Precipitation ................................................. 111
Unknown Precipitation ............................................ 111
Visibility Types ............................................................. 111
Fog.......................................................................... 111
Haze and Mist......................................................... 112
Weather Classes ......................................................... 112
Weather Code Selection .............................................. 113
Applications.......................................................................... 113
Internal Monitoring .............................................................. 114
Built-in Tests ..................................................................... 114
Memory Tests ................................................................... 115
Signal Monitoring .............................................................. 115
Hardware Monitoring......................................................... 115
Contamination Monitoring................................................. 116
CHAPTER 6
MAINTENANCE ......................................................................................... 117
General.................................................................................. 117
Cleaning ................................................................................ 118
Cleaning Lenses and Hoods............................................. 118
Cleaning DRD12 Rain Detector........................................ 118
Calibration ............................................................................ 119
General ............................................................................. 119
Visibility Calibration........................................................... 119
Calibration Check Procedure....................................... 120
Calibration Procedure .................................................. 123
Calibrating the DTS14B Temperature Sensor............. 124
Removing and Replacing.................................................. 126
Removing and Replacing Optical Units ....................... 126
Removing and Replacing the DRD12 Rain Detector .. 129
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Calibrating FD12P Weather Sensor after Unit
Replacement ................................................................130
CHAPTER 7
TROUBLESHOOTING................................................................................133
Warnings ...............................................................................133
Troubleshooting Examples..................................................133
Message Indicating Warning or Alarm .............................133
Message Missing ............................................................... 134
Visibility Value is Missing...................................................135
Visibility Value is Continuously Too Good ......................... 135
Visibility is Constantly Too Low .........................................136
FDP12 Reports Precipitation When There Is None........... 136
FD12P Reports Frozen Precipitation during Rain ............. 136
Have Jumper Settings Been Changed? ............................137
Values for Internal Monitoring.............................................137
Getting Help ..........................................................................140
Return Instructions...............................................................140
APPENDIX A
NWS AND WMO CODES USED IN FD12P ...............................................143
The NWS Codes ....................................................................143
APPENDIX B
JUMPER SETTINGS AND INTERNAL WIRING........................................147
CPU Board.............................................................................149
DC-Regulator.........................................................................149
DRI21 Interface Board ..........................................................149
APPENDIX C
TRANSMITTER AND RECEIVER TEST POINTS .....................................151
INDEX .........................................................................................................153
List of Figures
Figure 1 FD12P Weather Sensor Site ....................................................18
Figure 2 DRD12 Rain Detector and DTS14B Temperature Sensor .......19
Figure 3 FD12P Block Diagram ..............................................................21
Figure 4 Recommended Location for the FD12P ................................... 31
Figure 5 FD12P Equipment Grounding ..................................................33
Figure 6 Casting a Concrete Foundation................................................37
Figure 7 Constructing the FD12P Foundation ........................................ 39
Figure 8 Tilting the Pole Mast ................................................................. 41
Figure 9 DTS14B and the Sensor Holder Assembly to Mast .................42
Figure 10 Connecting Internal Grounding.................................................43
Figure 11 Cabling Principle.......................................................................44
Figure 12 Line Voltage and ON/OFF Switches.........................................45
Figure 13 Electronics Enclosure Feedthroughs........................................46
Figure 14 Cable Grounding Instructions ...................................................47
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Figure 15 Wiring the Connector for the LM11 Background Luminance
Meter ........................................................................................ 49
Figure 16 Wiring the Day/Night Photo Switch .......................................... 50
Figure 17 Communication Option ............................................................ 51
Figure 18 RS-485 Communication Option ............................................... 52
Figure 19 Wiring the Modem.................................................................... 53
Figure 20 Analog Current Loop Option .................................................... 55
Figure 21 FD12P Optical System............................................................. 96
Figure 22 FDT12B Transmitter Block Diagram........................................ 97
Figure 23 FDR12 Receiver Block Diagram .............................................. 98
Figure 24 DRI21 Block Diagram in the FD12P Application.................... 100
Figure 25 DRD12 Block Diagram........................................................... 101
Figure 26 FDP12 Control Unit Block Diagram ....................................... 102
Figure 27 Optical Raw Data (in Rain) .................................................... 103
Figure 28 Optical Signal Amplitude Distribution (in Rain) ...................... 104
Figure 29 DRD12 Surface Signal (Heavy Rain Beginning).................... 104
Figure 30 Precipitation Type Determination Principle ............................ 109
Figure 31 Assembling the FDA13 Calibrator.......................................... 122
Figure 32 DTS14 Sensor Holder Assembly to Mast .............................. 125
Figure 33 Removing the Optical Units ................................................... 127
Figure 34 Replacing the Optical Units.................................................... 128
Figure 35 Removing the DRD12 Rain Detector ..................................... 129
Figure 36 Basic Electronics Enclosure Wiring ....................................... 148
Figure 37 Test Points, Transmitter......................................................... 151
Figure 38 Test Points, Receiver ............................................................. 152
List of Tables
Table 1 Manual Revisions..................................................................... 12
Table 2 Related Manuals ...................................................................... 12
Table 3 Basic Set .................................................................................. 23
Table 4 Options..................................................................................... 23
Table 5 Mains Cable Selection ............................................................. 35
Table 6 Communication Cable Lengths................................................ 35
Table 7 Transmit Frequencies of the DMX21 Modem Board ............... 53
Table 8 LED Indicators of the DMX21 Modem ..................................... 54
Table 9 Manual Controls of the DMX21 Modem................................... 54
Table 10 Default Communication Settings.............................................. 57
Table 11 Commands for Changing the Default Settings ........................ 57
Table 12 Commands for Displaying and Changing the Parameters ...... 57
Table 13 Settings and Corresponding Commands................................. 60
Table 14 Routine Command for Maintenance ........................................ 60
Table 15 Status Report Command ......................................................... 60
Table 16 Transmitter Status Correspondence between MITRAS and
FD12P ...................................................................................... 67
Table 17 Receiver Status Correspondence between MITRAS and FD12P67
Table 18 HELP Command Sets .............................................................. 70
Table 19 Commands for Displaying or Setting Weather Analysis
Parameters............................................................................... 73
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Table 20 Commands for Displaying System Parameters and Editing the
Current System Configuration ..................................................79
Table 21 Maintenance Commands..........................................................85
Table 22 Hardware Error Texts ...............................................................86
Table 23 Hardware Warning Texts ..........................................................86
Table 24 Parameters for Optical Measurement.....................................131
Table 25 Parameters for DRD12 Precipitation Detector .......................131
Table 26 Parameters for DTS14 Temperature Sensor..........................131
Table 27 Updating Parameters..............................................................131
Table 28 Parameters and Commands...................................................132
Table 29 Values for Internal Monitoring.................................................138
Table 30 Internal Weather Types, NWS Code .....................................143
Table 31 WMO SYNOP Codes (4680, W
Table 32 WMO SYNOP Codes (4680, W
Table 33 WMO SYNOP Codes (4680, W
) ......................................143
aWa
) ......................................144
aWa
) ......................................144
aWa
Table 34 WMO Code Table 4678. Codes Used by FD12P ...................145
Table 35 CPU Board Jumpers...............................................................149
Table 36 CPU Board Connectors ..........................................................149
Table 37 DC-regulator Connectors........................................................149
Table 38 DRI21 Interface Board Jumpers ............................................. 149
Table 39 DRI21 Interface Board Connectors ........................................150
Table 40 Electronics Enclosure/Transducer Cable Signals ..................150
Table 41 Transmitter Test Points........................................................... 151
Table 42 Receiver Test Points............................................................... 152
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Chapter 1 _________________________________________________________ General Information
CHAPTER 1
GENERAL INFORMATION
About This Manual
This manual is a general information source as well as a detailed
operational guide to the FD12P Weather Sensor.
Contents of This Manual
This manual consists of the following chapters:
- Chapter 1, General Information, provides important safety, revision
history, contact, and warranty information for the product.
- Chapter 2, Product Overview, introduces the FD12P Weather
Sensor features, advantages, and the product nomenclature.
- Chapter 3, Installation, provides you with information to help you
install this product.
- Chapter 4, Operation, contains information needed to operate this
product.
- Chapter 5, Functional Description, gives a functional description on
the product.
- Chapter 6, Maintenance, describes the overall maintenance of the
product.
- Chapter 7, Troubleshooting, deals with troubleshooting
information.
- Appendix A, NWS and WMO Codes Used in FD12P
- Appendix B, Jumper Settings and Internal Wiring
- Appendix C, Transmitter and Receiver Test Points
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Version Information
Table 1 Manual Revisions
Manual Code Description
FD12P-U106en-1.2 Weather Sensor, User's Guide
M210296en-A This manual.
Related Manuals
Table 2 Related Manuals
Manual Code Manual Name
DMX21T0496-1.1 DMX21 CCITT Modem
LM11T0545-1.2 LM11 Background Luminance Meter
Safety
WARNING
CAUTION
General Safety Considerations
Throughout the manual, important safety considerations are
highlighted as follows:
Warning alerts you to a serious hazard. If you do not read and follow
instructions very carefully at this point, there is a risk of injury or
even death.
Caution warns you of a potential hazard. If you do not read and
follow instructions carefully at this point, the product could be
damaged or important data could be lost.
NOTE
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Note highlights important information on using the product.
Chapter 1 _________________________________________________________ General Information
Product Related Safety Precautions
The FD12P Weather Sensor delivered to you has been tested for
safety and approved as shipped from the factory. Note the following
precautions:
WARNING
CAUTION
WARNING
Ground the product, and verify outdoor installation grounding
periodically to minimize shock hazard.
Do not modify the unit. Improper modification can damage the
product or lead to malfunction.
Safety Summary
The following are general safety precautions must be observed during
all phases of installation, operation and maintenance.
Neglecting to follow these precautions or specific warnings and
cautions elsewhere in this manual violates safety standards of design,
manufacture and intended use of the instrument. Vaisala Oyj. and its
Subsidiaries do not answer for the consequences if the customer
neglects to follow these requirements.
Ground the Equipment
To minimize the hazard of electrical shock, follow accurately the
installation procedure in Chapter 3, Installation, on page 29.
NOTE
VAISALA ________________________________________________________________________ 13
Note that the chassis of the FD12P Weather Sensor must be
connected to a good electrical earth. The instrument is equipped with
a three-conductor AC power cable. Be sure that the earth wire of the
cable is connected to an electrical ground.
There is also a grounding clamp at the bottom of the electronics
enclosure of Weather Sensor FD12P. Good grounding with a 16-mm
2
User's Guide _______________________________________________________________________
cable must be provided. Besides increasing safety, this also protects
the Weather Sensor against lightning induced voltages.
To prevent operator injury or damage to the Weather Sensor, check
that the LINE VOLTAGE SETTING is correct before connecting the
line power (See Figure 12 on page 45.) Also ensure that the line power
outlet is provided with a protective ground contact.
WARNING
WARNING
WARNING
Do not operate in an explosive atmosphere.
Do not operate the equipment in the presence of flammable gases or
fumes. Operation of any electrical instrument in such an environment
constitutes a definite safety hazard.
Do not service or adjust alone.
Do not attempt internal service or adjustment unless another person,
capable of rendering first aid and resuscitation, is present.
Keep away from live circuits.
Component replacement or internal adjustments must be made by
qualified maintenance personnel. Operating personnel must not
remove instrument covers. Do not remove or replace any components
with the power cable connected. Under certain conditions, dangerous
voltages may exist even with the power cable disconnected. To avoid
injuries disconnect power, and discharge all circuits before touching
them.
WARNING
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Do not substitute parts or modify the instrument.
Because of the danger of introducing additional hazards, do not
modify or substitute parts in the instrument. Contact Vaisala or its
authorized representative for repairs to ensure that safety features are
maintained.
Chapter 1 _________________________________________________________ General Information
CAUTION
The component boards including CMOS microchips should be
transported and stored in conductive packages. Although new CMOS
devices are protected against overvoltage damages caused by static
electric discharge of the operator, careful handling is recommended:
the operator should be properly grounded. Unnecessary handling of
component boards should be avoided.
Radio Frequency Interference Statement (USA)
The United States Federal Communications Commission (in 47 CFR
15.838) has specified that the following notice must be brought to the
attention of users of this kind of a product in the USA:
Federal communications commission radio frequency interference
statement
This equipment generates and uses radio frequency energy and if not
installed and used properly, that is in strict accordance with the
manufacturer's instructions, may cause interference to radio and
television reception. The Weather Sensor is designed to provide
reasonable protection against such interference in an airport
installation. However, there is no guarantee that interference will not
occur in a particular installation. If this equipment causes
interference to radio or television reception, which can be determined
by turning the equipment off and on, the user is encouraged to try to
correct the interference by one or more of the following measures:
- reorient the receiving antenna
- relocate this device with respect to the receiver
- move this device away from the receiver
If necessary, the user should consult the dealer or an experienced
radio/television technician for additional suggestions.
ESD Protection
Electrostatic Discharge (ESD) can cause immediate or latent damage
to electronic circuits. Vaisala products are adequately protected
against ESD for their intended use. However, it is possible to damage
the product by delivering electrostatic discharges when touching,
removing, or inserting any objects inside the equipment housing.
VAISALA ________________________________________________________________________ 15
User's Guide _______________________________________________________________________
To make sure you are not delivering high static voltages yourself, take
the following precautions:
- Handle ESD sensitive components on a properly grounded and
protected ESD workbench. When this is not possible, ground
yourself to the equipment chassis before touching the boards.
Ground yourself with a wrist strap and a resistive connection cord.
When neither of the above is possible, touch a conductive part of
the equipment chassis with your other hand before touching the
boards.
- Always hold the boards by the edges and avoid touching the
component contacts.
Trademarks
Intel® is a registered trademark of the Intel Corporation in the U.S.
and other countries.
Warranty
For certain products Vaisala normally gives a limited one-year
warranty. Please observe that any such warranty may not be valid in
case of damage due to normal wear and tear, exceptional operating
conditions, negligent handling or installation, or unauthorized
modifications. Please see the applicable supply contract or conditions
of sale for details of the warranty for each product.
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Chapter 2 ___________________________________________________________Product Overview
CHAPTER 2
PRODUCT OVERVIEW
This chapter introduces the FD12P Weather Sensor features,
advantages, and the product nomenclature.
Introduction
The FD12P Weather Sensor is an intelligent, multi-variable sensor for
automatic weather stations and airport weather observing systems.
The sensor combines the functions of a forward scatter visibility meter
and a present weather sensor. In addition, the sensor can measure the
intensity and amount of both liquid and solid precipitation.
The FD12P can be used to automatically determine the visibility and
precipitation related weather codes in the World Meteorological
Organization (WMO) standard SYNOP and METAR messages. The
sensor can also be employed as an observer's aid in a semi-automatic
weather observing system. The sensor is also suitable for other
weather observing systems providing valuable information, for
example, to road and harbor authorities.
The versatility of the FD12P is achieved with a unique operating
principle. The FD12P measures precipitation water content with a
capacitive device and combines this information with optical scatter
and temperature measurements. These three independent
measurements together provide data sufficient for an accurate
evaluation of current visibility and weather type.
Hardware Structure
The structural basis of the FD12P is the pole mast that supports the
transducer crossarm (FDC115). The crossarm contains the optical
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units, FDT12B Transmitter and FDR12 Receiver. The DRD12 Rain
Detector is fastened to the crossarm. The electronics enclosure with
the main data processing and interface units is mounted to the pole
mast as seen in Figure 1 below.
0201-085
Figure 1 FD12P Weather Sensor Site
The following numbers are related to Figure 1 above:
1 = Transducer crossarm
2 = DRD12 Rain Detector
3 = DTS14 Temperature Sensor
4 = Pole mast
5 = Electronics enclosure
The FD12P Weather Sensor consists of three parts: sensing elements,
electronics enclosure, and structural elements. They are described in
detail on the next page.
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Chapter 2 ___________________________________________________________Product Overview
Sensing Elements
The FDT12B Transmitter emits pulses of near infrared light. It is
permanently tilted 16.5º downwards. The optical power is stabilized
by a closed hardware loop. The unit also includes a receiver circuit for
monitoring lens contamination.
The FDR12 Receiver measures the scattered part of the FDT12B light
beam. The FDR12 contains also an additional light transmitter for
monitoring lens contamination. Like the transmitter, the receiver is
also tilted 16.5º downwards. Therefore, the receiver unit measures
light scattered at an angle of 33°.
The DRD12 Rain Detector outputs a signal proportional to the amount
of water on two RainCap™ sensing elements. These elements consist
of thin wires protected by an insulating glass coating. The presence of
water changes the capacitance of the elements. The combined
capacitance of the plates is measured by the DRD12 electronics.
Integrated heating resistors keep the elements dry when, for example,
fog and melt snow fall on them. The Rain Detector is protected by a
windshield to decrease the effect of wind on the measurement results.
The DRD12 is illustrated in Figure 2 below.
The DTS14B Temperature Sensor is a Pt100 thermistor that is used to
measure the crossarm temperature. See Figure 2 below.
0201-086
Figure 2 DRD12 Rain Detector and DTS14B Temperature
Sensor
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The following numbers refer to Figure 2 on page 19:
1 = Two RainCapTM elements
2 = DRD12 Rain Detector
3 = Wind shield
4 = Assembly clamp
5 = DTS14 Temperature sensor
Electronics Enclosure
The FDP12 Control Unit is the main data processor and
communication unit of the FD12P.
The DRI21 Interface Board is a Vaisala, general-purpose sensor
interface, with several analog and digital input channels. In the
FD12P, one of the DRI21 Interface Board channels is used for
measuring the crossarm temperature and the DRD12 analog signal. In
addition, the DRI21 controls the DRD12 heating and reads the
precipitation ON/OFF status.
The FDW13 Mains Power Supply converts the mains voltage to
24 VAC power for the FDS12 regulator and the heater elements. The
FDW13 includes also the mains voltage selector and the mains
ON/OFF switch, which also functions as an automatic fuse.
The FDS12 DC Voltage Regulatorconverts the AC or DC input
voltage (min. 18 V) to 12 VDC power used by FD12P electronics. The
FDS12 also includes one relay used to control heater power.
The DMX21 Modem (optional) is a standard, 300-baud modem used
only in the leased line mode with the FD12P.
The FDE12 Backup Temperature Sensor is included.
Structural Elements
The structural elements include the pole mast with a standard height
of 2 meters and the FDC115 Transducer Crossarm with a length of
1.5 meters, which is also the total width of the FD12P.
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Chapter 2 ___________________________________________________________Product Overview
Operating Principle
The FD12P Weather Sensor is a microprocessor controlled, intelligent
sensor combining optical forward scatter measurement, capacitive
precipitation sensing, and temperature measurement. The main units
of the FD12P are shown in Figure 3 below.
9502-091
Figure 3 FD12P Block Diagram
The FD12P evaluates Meteorological Optical Range (MOR) by
measuring the intensity of infrared light scattered at an angle of 33°.
The scatter measurement is converted to the visibility value (MOR)
after a careful analysis of the signal properties. Special processing is
used in case of precipitation.
The FD12P software detects precipitation droplets from rapid changes
in the scatter signal. The droplet data is used to estimate optical
precipitation intensity and amount. In addition to the optical signal,
the analog output of the DRD12 Rain Detector is used to estimate the
precipitation intensity and type.
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The output of the DRD12 is proportional to the water amount on the
capacitive sensing surfaces while the optical intensity is proportional
to the total volume of the reflecting particles. The ratio of optical and
capacitive intensities is used to determine the basic precipitation type.
The crossarm temperature (TS) is measured with the DTS14B
Temperature Sensor connected to the DRI21 interface card. The
temperature data together with the optical signal profile and the
DRD12 surface sensor data are used to determine the actual weather
code.
The software performs all signal analyses in the FD12P except the
DRD12 Rain ON/OFF status, which is hardware-based and is used as
an auxiliary parameter. The FD12P has a fixed program that is divided
into tasks executed under control of a real-time operating system
kernel. Each task is like an endless loop with a limited function. The
operating system kernel controls the timing of the tasks and the
interactions between the tasks.
Using FD12P
The FD12P is typically used as a component of a weather observing
system. The final weather message (SYNOP, METAR) is then coded
in the central unit of a weather observation system (for example,
Vaisala MILOS 500) or by a human observer using the FD12P as an
observation aid.
The FD12P output is a digital serial interface, which can be
configured into two different operating modes: the sensor can be set to
send a data message automatically at selected intervals, or the FD12P
can be polled by the host computer. The same serial line is also used
as an operator interface.
The operator controls and checks the operation of the FD12P by using
a maintenance terminal. A set of built-in commands and test routines
is provided for configuring and monitoring the multiple functions of
the FD12P.
The standard data messages contain a status character for indicating
faults detected by the internal diagnostics. If the error status is set, the
operator can view a special status message. It contains detailed results
of the diagnostics and a written description of the fault. Using this
information, the operator can take corrective action or provide the
maintenance personnel with valuable advice.
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Chapter 2 ___________________________________________________________Product Overview
Equipment Nomenclature
The standard equipment nomenclature and common names are listed
in Table 3 and Table 4 below.
Table 3 Basic Set
Type Name Description
FDC115 Transducer Crossarm Optics, analog, monitoring
assembly
FDT12B Transmitter
FDR12 Receiver
16614ZZ Crossarm Cable
FDB12 Electronics Enclosure Power, conversions, interfacing
assembly
FDP12 Processor Board
FDS12 DC Voltage Regulator
FDW13 Mains Power Supply
DRI21 Interface Board
16615ZZ Transducer Cable
16737ZZ I/O Bus Cable
DRD12 Rain Detector
FD30513 Pole Mast Standard 2-m mast
13145 Base Plate and
Installation Set
Table 4 Options
Type Name Description
FDA13 Visibility Calibration Set
FD45094 Maintenance cable RS232 cable with 9-pin D-
connector.
Termbox-48 Mains and Signal
Junction Box
FD12MODEM Modem Option For remote communication.
FD12PLM11 LM11 Option For ambient light
16616ZZ Extended Transducer
Cable
Adapting/extending the local
cable. Contains heavy-duty
transient protection circuitry.
measurement.
For optional high-mast
mounting.
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Specifications
Mechanical Specifications
- Dimensions: 2.3 m × 1.6 m × 0.6 m (H × W × D)
- Weight: 35 kg, excluding the installation plate for the pole
mast
- Mounting: on a concrete foundation with three ∅16-mm
bolts
- Material: anodized aluminum, natural gray
Electrical Specifications
- Mains supply: 115/230 VAC ± 20 %, 45 ... 65 Hz
- Maximum power consumption: 35 W + 100 W defrosting
heaters (in cold weather)
The sensor electronics:
- Lock-in amplifier
- LED power stabilizer
- Contamination monitor
- Lens heater
The control unit:
- Intel 8031 microprocessor
- Program memory, 64 Kbytes
- Read/write memory, 32 Kbytes
Outputs:
- Serial data line may be used either as RS-232 level signals or
interfaced via an optional data modem
- RS-485 (2-wire)
- 4 - 20 mA analog current (sink) output
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Chapter 2 ___________________________________________________________Product Overview
The output data:
- Automatic or polled data message
- Visibility, present weather, precipitation and status data
- Automatic message type and interval is selectable at 15
seconds to n × 15 seconds (n < 18) intervals
The analog visibility output:
- Selectable range and mode (linear or logarithmic)
- Status control bit for remote alarm relay, etc.
- Alarms and warnings (hardware failures, visibility limits)
Optical Specifications
Operating principle:
- Forward scatter at an angle of 33o and capacitive rain sensor.
The light transmitter:
- Light source: near-infrared LED
- Peak wavelength: 875 nm
- Modulation frequency: 2.3 kHz
- Transmitter lens diameter: 71 mm
- Reference photodiode: for light source control
- Backscatter photodiode: for contamination and blockage
measurement
The light receiver:
- Photodiode: PIN 6 DI
- Spectral response: max. responsivity at 850 nm, 0.55 A/W
(in range 550 ... 1050 nm over 0.3 A/W)
- Reception lens diameter: 71 mm
- Backscatter light source: near-infrared LED for
contamination and blockage measurement
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Capabilities and Limitations
Visibility Measurement Specifications
Measurement range of Meteorological Optical Range (MOR):
- 10 ... 50 000 m according to a 5 % Contrast Threshold
Definition
Accuracy:
- ± 10 %, range 10 ... 10 000 m
- ± 20 %, range 10 000 ... 50 000 m
Instrument consistency:
- + 4 %
Update interval:
- 15 seconds
Weather Sensing Specifications
Precipitation detection sensitivity:
- 0.05 mm/h or less, within 10 minutes
Weather type identification:
- 11 different types of precipitation
- Fog (mist) and haze (smoke, sand)
Weather type reporting:
- WMO code table 4680 (with some additions from code table
4677)
- Code letters for precipitation, NWS
- WMO code table 4678 (supported codes are shown in Table
34 on page 145).
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Chapter 2 ___________________________________________________________Product Overview
Precipitation intensity measurement:
- Range 0.00 ... 999 mm/h
- Accuracy ± 30 % (range 0.5 ... 20 mm/h, liquid precipitation)
Environmental Specifications
Operating temperature range:
- − 40 ... +55 oC
Operating humidity range:
- Up to 100 % RH
Wind speed:
- Up to 60 m/s (standard mast)
Sun orientation:
- Direct and reflected sunlight into the light receiver must be
avoided.
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Chapter 3 ________________________________________________________________ Installation
CHAPTER 3
INSTALLATION
This chapter provides you with information to help you install this
product.
NOTE
Before installation, read section Product Related Safety Precautions
on page 13.
Organizing Installation
Before you begin to install the FD12P Weather Sensor, make a plan of
the installation steps. The following is an example of how to organize
the installation process.
1. Surveying the site:
- Find the most representative measurement site.
- Determine orientation of the Weather Sensor.
2. Cabling plan is required for the following:
- Grounding cabling layout and cable type.
- Power supply cabling layout and cable type.
- Modem/signal cabling layout and cable type.
3. Ordering the construction materials and cables.
4. Digging for cables and foundation.
5. Casting the concrete:
- Prepare concrete blocks by using a casting mold.
- Cast the fixing bolts in their places at the same time.
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6. Installing the base plate and the pole mast:
- Install the base plate with the bolts on the concrete block.
- Level the plate.
- Mount the pole mast on the base plate.
- Mount the junction box to the pole mast (optional). Junction
boxes are available from Vaisala.
7. Connecting cables:
- Connect the mains and signal cables of the site to the junction
box or have them ready for direct connection to the sensor.
8. Final installation:
- Install the electronics enclosure and the crossarm of the
FD12P to the pole mast.
- Connect the power and signal cables of the FD12P.
- Connect the modem/signal line to the host computer, display,
etc.
9. Start-up tests for the system.
Location and Orientation
The main requirements for the location of the FD12P are as follows:
1. Place the FD12P at a site where the measurements will be
representative of the surrounding weather conditions.
The ideal site has a minimum clearance of 100 meters from all
large buildings and other constructions that generate heat and/or
obstruct precipitation droplets. Also avoid shading of trees as
this may cause changes in the microclimate.
2. Make sure the site is free of obstacles and reflective surfaces,
which disturb the optical measurements and act as obvious
sources of contamination.
There must not be any obstacles in the line-of-sight of the
transmitter and receiver units (see Figure 4 on page 31). If the
transmitter beam is reflected from obstacles back to the receiver
unit, the sensor will indicate too low MOR values as the
reflected signal cannot be distinguished from the real scatter
signal. Reflections are detected by rotating the sensor crossarm.
They will change depending on the crossarm orientation. Also
the visibility reading will change accordingly.
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