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INSTRUCTION MANUAL
Met One 034A-L Windset
Revision: 7/97
Copyright (c) 1980-1997
Campbell Scientific, Inc.
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Warranty and Assistance
The MET ONE 034A-L WINDSET is warranted by CAMPBELL
SCIENTIFIC, INC. to be free from defects in materials and workmanship under
normal use and ser vice for twelve (1 2) months from date of shipment unless
specified otherwise. Batteries have no warranty. CAMPBELL SCIENTIFIC,
INC.'s obligation under this warranty is limited to repairing or replacing (at
CAMPBELL SCIENTIFIC, INC.'s option) defective products. The customer
shall assume all costs of removing, reinstalling, and shipping defective products
to CAMPBELL SCIENTIFIC, INC. CAMPBELL SCIENTIFIC, INC. will
return such products by surface carrier prepaid. This warranty shall not apply
to any CAMPBELL SCIENTIFIC, INC. products which have been subjected to
modification, misuse, neglect, accidents of nature, or shipping damage. This
warranty is in lieu of all other warranties, expressed or implied, including
warranties of merchantability or fitness for a particular purpose. CAMPBELL
SCIENTIFIC, INC. is not liable for special, indirect, incidental, or
consequential damages.
Products may not be returned without prior authorization. The following
contact information is for US and International customers residing in countries
served by Campbell Scientific, Inc. directly. Affiliate companies handle repairs
for customers within their territories. Please visit www.ca mpbellsci.co m to
determine which Campbell Scientific company serves your country. To obtain
a Returned Materials Authorization (RMA), contact CAMPBELL
SCIENTIFIC, INC., phone (435) 753-2342. After an applications engineer
determines the nature of the problem, an RMA number will be issued. Please
write this number clearly on the outside of the shipping container.
CAMPBELL SCIENTIFIC's shipping address is:
CAMPBELL SCIENTIFIC, INC.
RMA#_____
815 West 1800 North
Logan, Utah 84321-1784
CAMPBELL SCIENTIFIC, INC. does not accept collect calls.
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034A-L Table of Contents
PDF viewers note: These page numbers refer to the printed version of this document. Use
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1. General........................................................................1
2. Specifications .............................................................1
3. Installation...................................................................1
3.1 Siting.........................................................................................................1
3.2 Mounting...................................................................................................1
4. Wiring ..........................................................................2
5. Datalogger Programming...........................................3
6. Sensor Maintenance...................................................6
7. Long Lead Lengths.....................................................6
8. Wind Direction Measurement Theory........................8
8.1 AC Half Bridge (P5).................................................................................8
8.2 DC Half Bridge (P4).................................................................................8
9. References ..................................................................8
Appendix
A. Wind Direction Sensor Or ientation.......................A-1
A.1 Determining True North and Sensor Orientation.................................A-1
A.2 Prompts from GEOMAG.....................................................................A-2
Figures
3-1. 034A-L Mounted on a 019ALU Horizontal Crossarm............................2
4-1. 034A-L Windset Wiring Diagram........................................................... 3
8-1. 034A-L Potentiometer in a Half Bridge Circuit.......................................8
A-1. Magnetic Declination for the Contiguous United States.....................A-1
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034A-L Table of Contents
Table
A-2. Declination Angles East of True North Are Subtracted from 0
to Get True North......................................................................... A-2
A-3. Declination Angles West of T rue North Are Added to 0
to Get True North......................................................................... A-3
5-1. Multipliers and Offsets for Wind Speed and Direction........................... 4
7-1. Multiplier and Offset for Wind Direction when using
Lead Lengths Greater than 200 Feet................................................6
ii
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MET ONE 034A-L WINDSET
1. GENERAL
The Met One 034A-L Windset is an integrated
cup anemometer and wind vane. The
anemometer consists of three cups that sense
the wind speed. These cups rotate on a vertical
shaft that magnetically activates a sealed reed
switch. The read switch opens and closes at a
rate proportional to wind speed. The wind
direction is sensed by a vane. The vane drives a
10 kΩ potentiometer.
2. SPECIFICATIONS
Wind Speed
Operating Range: 0 to 49 m s
-1
Threshold: 0.4 m s
(0.9 mph)
Accuracy:
±0.12 m s
speed < 10.1 m s
±1.1% of reading for wind
speeds > 10.1 m s
-1
(±0.25 mph) for wind
-1
(22.7 mph)
-1
Output Signal: contact closure (reed switch)
Wind Direction
Range: 0 to 360°, shorting to ground between
356° to 360°
Threshold: 0.4 m s
-1
(0.9 mph)
Accuracy: ±4°
Resolution: 0.5°
Potentiometer Specifications:
Resistance: 0 to 10 kΩ shorting at crossover
General Specifications
Operating Temperature Range: -30° to +70°C
Weight: 907 g (2.0 lb.)
NOTE: The black outer jacket of the cable is
Santoprene® rubber. This compound was
chosen for its resistance to temperature
extremes, moisture, and UV degradation.
However, this jacket will support combustion in
air. It is rated as slow burning when tested
according to U.L. 94 H.B. and will pass
FMVSS302. Local fire codes may preclude its
use inside buildings.
-1
(0 to 110 mph)
(22.7 mph)
3. INSTALLATION
3.1 SITING
Locate wind sensors away from obstructions
(e.g. trees and building). As a general rule of
thumb there should be a horizontal distance of
at least ten times the height of the obstruction
between the windset and the obstruction. If it is
necessary to mount the sensors on the roof of a
building, the height of the sensors, above the
roof, should be at least 1.5 times the height of
the building. See Section 9 for a list of
references that discuss siting wind speed and
direction sensors.
3.2 MOUNTING
Tools Required:
• 5/64” and 1/16” allen wrenches
• compass and declination angle for the site
• small screw driver provided with datalogger
• UV resistance cable ties
• small pair of diagonal-cutting pliers
• 6 - 10” torpedo level
Mount the 019ALU crossarm to the top of the
tripod/tower. Orient the 019ALU north and
south with the 3/4 x 1 inch Nu-Rail on the north
end. Appendix A contains detailed information
on determining true north using a compass and
the magnetic declination for the site.
Remove the alignment screw at the base of the
034A-L (Figure 3-1). Insert the 034A-L into the
aluminum bushing provided with the sensor.
Align the hole in the bushing with that in the
034A-L base and replace the screw. Insert the
034A-L/bushing into the 3/4 x 1 inch Nu-Rail on
the 019ALU. Align the sensor so that the
counter weight points to true south and tighten
the set screws on the Nu-Rail. Remove the
shoulder screw to allow the vane to rotate.
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MET ONE 034A-L WINDSET
Shoulder
Screw
Alignment
Screw
019ALU Crossarm
FIGURE 3-1. 034A-L Mounted on a 019ALU Horizontal Crossarm.
Attach the sensor cable to the six pin male
connector on the 034A-L. Make sure the
connector is properly keyed. Finger tighten the
knurled ring. Route the sensor cable along the
underside of the crossarm to the tripod/tower
mast and down a tripod/tower leg to the
instrument enclosure. Secure the cable to the
crossarm and mast using cable ties.
4. WIRING
The connection to the datalogger for the 034A-L
are shown in Figure 4-1. The wind speed is
measured by a pulse input channel. The wind
Bushing
N
3/4 x 1 inch Nu-Rail
direction is measured by a single-ended analog
input channel.
Connect the red lead to a pulse input channel
(wind speed) and the black lead to a ground,
labeled G on the CR10(X) or
Connect the green lead (wind direction) to a
single-ended input channel, the blue lead to an
excitation channel, and white lead to an analog
ground, labeled AG on the CR10(X), or ground,
labeled
to ground, labeled G on the CR10(X) or
the 21X.
on the 21X. Connect the clear lead
on the 21X.
on
2
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CONNECTOR PIN-OUT
3
4
2
6
5
1
PIN 1 - AZIMUTH SIGNAL
PIN 2 - AZIMUTH REFERENCE
PIN 3 - AZIMUTH EXCITATION
PIN 4 - PULSE OUT
PIN 5 - PULSE REFERENCE
PIN 6 - SHIELD
MET ONE 034A-L WINDSET
10K OHM AZIMUTH
POTENTIOMETER
MAGNETICALLY
ACTIVATED
REED SWITCH
ADJUSTABLE
RESISTANCE
1K OHM
CONNECTOR
(PIN)
FIGURE 4-1. 034A-L Windset Wiring Diagram
5. DATALOGGER PROGRAMMING
The Pulse instruction, Instruction 3, with an
option code of 22, is used to measure the wind
speed. Instruction 3 counts the number of
switch closures that have occurred during the
datalogger’s execution interval. When option
code 22 is selected, the datalogger reports the
counts as a frequency. In addition, counts
beyond the execution interval, caused by table
overruns, are discarded, see Section 9 of the
Datalogger manual for details. The frequency is
converted into wind speed using the multiplier
and offset listed in Table 5-1.
Datalogger
9.53K OHM
3
1
BLUE
GREEN
WHITE
2
4
5
RED
BLACK
CLEAR
6
E3
SE5 or 3H
AG or
P2
G or
G or
(Switch
Excitation)
(Single-Ended
Analog Input)
(Pulse Input
The AC Half Bridge instruction, Instruction 5, is
used to measure wind direction. The AC Half
Bridge (P5) instruction provides a precision
voltage to the potentiometer and measures the
voltage between the wiper and ground. The
voltage is linearly proportional to the azimuth
and is converted to degrees by the multiplier
and offset listed in Table 5-1.
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MET ONE 034A-L WINDSET
TABLE 5-1. Multipliers and Offsets for Wind
Speed and Direction
Units Datalogger
type
-1
m s
CR10(X)
or 21X
mph CR10(X)
or 21X
degrees CR10(X)
or 21X
Instruction
number
3 0.7990
3 1.789
5 720
Multiplier
Offset
0.2811
.629
0
EXAMPLE 1. Sample CR10(X) Instructions
;{CR10X}
;
*Table 1 Program
01: 10 Execution Interval (seconds)
01: Pulse (P3)
1: 1 Reps
2: 2* Pulse Channel 2
3: 22 Switch Closure, Output Hz
4: 1* Loc [ WndS_m_s ]
5: 0.7990 Mult
6: 0.2811 Offset
NOTE: 034A-L Windsets purchased
directly from Met One Instruments have a
different configuration on the 6 pin
connector. In addition, they do not have the
10 kΩ resistor on the excitation line. The
wiring diagram and the multiplier and offset,
for wind direction, are different than the
examples in this document.
;Set the wind speed to zero if the wind is not blowing.
;
02: If (X<=>F) (P89)
1: 1* X Loc [ WndS_m_s ]
2: 1 =
3: 0.2811 F
4: 30 Then Do
03: Z=F (P30)
1: 0 F
2: 0 Exponent of 10
3: 1* Z Loc [ WndS_m_s ]
04: End (P95)
05: AC Half Bridge (P5)
1: 1 Reps
2: 25 ± 2500 mV 60 Hz Rejection Range
3: 5* SE Channel
4: 3* Excite all reps w/Exchan 3
5: 2500 mV Excitation
6: 2* Loc [ WndD_deg ]
7: 720 Mult
8: 0 Offset
06: If time is (P92)
1: 0 Minutes (Seconds --) into a
2: 30 Interval (same units as above)
3: 10 Set Output Flag High (Flag 0)
4
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07: Real Time (P77)
1: 0110 Day,Hour/Minute
08: Wind Vector (P69)
1: 1 Reps
2: 0 Samples per Sub-Interval
3: 00 S, θu, & σ(θu) Polar**
4: 1* Wind Speed [ WndS_m_s ]
5: 2* Wind Direction [ WndD_deg ]
-Input Locations1 WndS_m_s
2 WndD_deg
EXAMPLE 2. Sample 21X Instructions
;{21X}
;
*Table 1 Program
01: 10 Execution Interval (seconds)
01: Pulse (P3)
1: 1 Reps
2: 2* Pulse Channel 2
3: 22 Switch Closure, Output Hz
4: 1* Loc [ WndS_m_s ]
5: 0.7990 Mult
6: 0.2811 Offset
MET ONE 034A-L WINDSET
;Set the wind speed to zero if the wind is not blowing.
;
02: If (X<=>F) (P89)
1: 1* X Loc [ WndS_m_s ]
2: 1 =
3: 0.2811 F
4: 30 Then Do
03: Z=F (P30)
1: 0 F
2: 1* Z Loc [ WndS_m_s ]
04: End (P95)
05: AC Half Bridge (P5)
1: 1 Reps
2: 5 ± 5000 mV Slow Range
3: 5* SE Channel
4: 3* Excite all reps w/Exchan 3
5: 5000 mV Excitation
6: 2* Loc [ WndD_deg ]
7: 720 Mult
8: 0 Offset
06: If time is (P92)
1: 0 Minutes (Seconds --) into a
2: 30 Interval (same units as above)
3: 10 Set Output Flag High (Flag 0)
5
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MET ONE 034A-L WINDSET
07: Real Time (P77)
1: 0110 Day,Hour/Minute
08: Wind Vector (P69)
1: 1 Reps
2: 0 Samples per Sub-Interval
3: 00 S, θu, & σ(θu) Polar**
4: 1* Wind Speed [ WndS_m_s ]
5: 2* Wind Direction [ WndD_deg ]
-Input Locations1 WndS_m_s
2 WndD_deg
* Proper entries will vary with program and datalogger
channel and input location assignments.
** Average wind speed, average unit vector wind direction,
standard deviation of unit vector wind direction
6. SENSOR MAINTENANCE
1 Month
• Do a visual/audio inspection of the
anemometer at low wind speeds. Verify
that the cup assembly and wind vane rotate
freely. Inspect the sensor for physical
damage. Verify cups and vane are tight.
6 Months
• Replace anemometer bearings if operating
under harsh conditions
1 Year
• Replace anemometer bearings. Contact
Campbell Scientific for a Return Materials
Authorization (RMA) number at (801) 753-
2342.
2 Years
• Replace the wind vane potentiometer and
bearings. Contact Campbell Scientific for a
Return Materials Authorization (RMA)
number at (801) 753-2342.
7. LONG LEAD LENGTHS
When lead lengths greater than 200 feet are
required to measure the 034A-L, use the DC
Half Bridge instruction, Instruction 4, with a 20
millisecond delay to measure wind direction.
The delay increases the settling time before the
measurement is made.
With a CR10(X), use a 2500 mV excitation and
the 2500 mV measurement range. With a 21X,
use a 5000 mV excitation and the 5000 mV
measurement range.
CAUTION: The 60 Hz rejection option can
not be used with the DC Half Bridge
instruction, when the delay is not zero. Do
not used long lead lengths in electrically
noisy environments.
TABLE 7-1. Multiplier and Offset for Wind
Direction when using Lead Lengths Greater
than 200 Feet
Units Datalogger
type
degrees CR10(X) 4 0.288
degrees 21X 4 0.144
Instruction
number
Multiplier
Offset
0
0
6
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EXAMPLE 3. Sample CR10(X) Program when Long Leads are Required
;{CR10X}
;
*Table 1 Program
01: 10 Execution Interval (seconds)
01: Pulse (P3)
1: 1 Reps
2: 2* Pulse Channel 2
3: 22 Switch Closure, Output Hz
4: 1* Loc [ WndS_m_s ]
5: 0.7990 Mult
6: 0.2811 Offset
;Set the wind speed to zero if the wind is not blowing.
;
02: If (X<=>F) (P89)
1: 1* X Loc [ WndS_m_s ]
2: 1 =
3: 0.2811 F
4: 30 Then Do
03: Z=F (P30)
1: 0 F
2: 0 Exponent of 10
3: 1* Z Loc [ WndS_m_s ]
MET ONE 034A-L WINDSET
04: End (P95)
05: Excite-Delay (SE) (P4)
1: 1 Reps
2: 5** ± 2500 mV Slow Range
3: 5* SE Channel
4: 3* Excite all reps w/Exchan 3
5: 2 Delay (units 0.01 sec)
6: 2500** mV Excitation
7: 2* Loc [ WndD_deg ]
8: 0.288 Mult
9: 0 Offset
06: If time is (P92)
1: 0 Minutes (Seconds --) into a
2: 30 Interval (same units as above)
3: 10 Set Output Flag High (Flag 0)
07: Real Time (P77)
1: 0110 Day,Hour/Minute
08: Wind Vector (P69)
1: 1 Reps
2: 0 Samples per Sub-Interval
3: 00 S, θu, & σ(θu) Polar***
4: 1* Wind Speed [ WndS_m_s ]
5: 2* Wind Direction [ WndD_deg ]
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MET ONE 034A-L WINDSET
(
-Input Locations-
1 WndS_m_s
2 WndD_deg
* Proper entries will vary with program and datalogger
channel and input location assignments.
** On the 21X use the 5000 mV input range and the
a 5000 mV excitation voltage.
*** Average wind speed, average unit vector wind direction,
standard deviation of unit vector wind direction
8. WIND DIRECTION MEASUREMENT THEORY
It is not necessary to understand the concepts
in this section for the general operation of the
034A-L Windset with Campbell Scientific’s
datalogger.
The 034A-L Windsets purchased from
Campbell Scientific have a 10 kΩ resistor on
the excitation line. This resistor prevents
erroneous measurements when the
potentiometer shorts to ground as the wind
direction crosses over from the west side of
north to the east side of north.
The maximum value that Rs will reach is 10 kΩ,
just before it crosses over from the west side of
north to the east side of north. V
its maximum value of 0.5 mV/mV at 360
degrees. Thus, the multiplier is 720 degrees.
Since the datalogger outputs the ratio V
the multiplier is the same for both the CR10(X)
and 21X dataloggers, even though they use a
different excitation voltage. See Section 13.5 in
the datalogger manual from more information
on the bridge measurements.
8.2 DC HALF BRIDGE, INSTRUCTION P4
Instruction 4 outputs a precise 2500 mV
excitation (5000 mV excitation with the 21X)
and measures the voltage between the wiper
and analog ground, V
the wiper and analog ground, R
with wind direction. Instruction 4 outputs the
measured voltage, V
is related to resistance as shown below:
VRRRR VR K
=⋅ ++ =⋅ 20 Ω
sxsft s xs
. The resistance between
s
. This measured voltage
s
)
reaches
s / Vx
, and Vs varies
s
s / Vx
,
The maximum value that Rs will reach is 10 kΩ
just before it crosses over from the west side of
FIGURE 8-1. 034A-L Potentiometer in a Half
Bridge Circuit
8.1 AC HALF BRIDGE, INSTRUCTION 5
Instruction 5 outputs a precise 2500 mV AC
excitation (5000 mV AC excitation with the 21X)
and measures the voltage between the wiper
and analog ground, V
the wiper and analog ground, R
with wind direction. Instruction 5 outputs the
ratio of the measured voltage to the excitation
voltage (V
resistance as shown below:
VRRRR R K
=++=20 Ω
sx s f t s s
8
). This ratio is related to
s / Vx
()
. The resistance between
s
, and Vs varies
s
north to the east side of north. V
maximum value of 1250 mV for the CR10(X) and
2500 mV for the 21X at 360 degrees. Thus, the
multiplier is 0.144 degrees/mV for the CR10(X)
and 0.288 degrees/mV for the 21X. See Section
13.5 in the datalogger manual from more
information on the bridge measurements
9. REFERENCES
The following references give detailed
information on siting wind speed and wind
direction sensors.
EPA, 1989: Quality Assurance Handbook for
Air Pollution Measurements System, Office of
reaches its
s
Page 13
Research and Development, Research Triangle
Park, NC, 27711.
EPA, 1987: On-Site Meteorological Program
Guidance for Regulatory Modeling Applications,
EPA-450/4-87-013, Office of Air Quality
Planning and Standards, Research Triangle
Park, NC 27711.
The State Climatologist, 1985: Publication of
the American Association of State
Climatologists: Height and Exposure
Standards, for Sensors on Automated Weather
Stations, vol. 9, No. 4.
WMO, 1983: Guide to Meteorological
Instruments and Methods of Observation, World
Meteorological Organization, No. 8, 5th edition,
Geneva, Switzerland.
MET ONE 034A-L WINDSET
9
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Campbell Scientific Companies
Campbell Scientific, Inc. (CSI)
815 West 1800 North
Logan, Utah 84321
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11564 - 149th Street NW
Edmonton, Alberta T5M 1W7
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