Campbell UT20 User manual

Revision: 03/2020
Copyright © 1993 – 2020
Campbell Scientific, Inc.

Table of contents
1. Introduction 1
2. Precautions 1
2.1 Site selection 1
2.2 Tower mounting 1
2.3 Tower installation 2
3. Initial inspection 2
3.1 Indoors 2
3.2 Outdoors 2
3.3 Tools required 3
4. Siting and exposure 3
4.1 Wind speed and direction 4
4.2 Temperature and relative humidity 4
4.3 Precipitation 5
4.4 Solar radiation 5
4.5 Soil temperature 6
4.6 Siting references 6
5. Overview 6
6. Specifications 8
7. Tower installation 9
7.1 Installing the tower 9
7.1.1 Base and Guy Anchor Layout 10
7.1.2 Tower base installation 11
7.1.2.1 UTBASE base installation 11
7.1.2.2 RFM18 base installation 20
7.1.3 Guy anchor installation 21
7.1.3.1 UTEYE eyebolt guy anchor 21
7.1.3.2 UTDUK duckbill guy anchor 22
7.1.4 Tower assembly 24
7.1.5 UTGND tower grounding kit 26
Table of Contents - i

7.1.6 Attaching the lightning rod 28
7.2 Crossarms and mounting brackets 29
7.2.1 CM202, CM203, CM204, CM206 Crossarms 29
7.2.2 CM230, CM230XL adjustable angle mounting kits 30
7.2.3 CMB200 crossarm brace kit 32
7.2.3.1 Components 33
7.2.3.2 Assembly 34
Appendix A. UTBASE paper template 37
Paper template, page 1 38
Paper template, page 2 39
Paper template, page 3 40
Table of Contents - ii

1. Introduction
The UT20 and UT30 are durable, lightweight instrument towers used for a variety of applications.
They support a 6 m (20 ft) or 9 m (30 ft) measurement height for wind sensors as well as sturdy
attachment points for antennas, solar panels, environmental enclosures, radiation shields, and
crossarms. A retractable mast at the top of the tower adds increased flexibility in the placement of
sensors at the top of the tower.
NOTE:
Throughout the manual, the term "tower" refers to both the UT20 and UT30, unless specified
otherwise.
2. Precautions
2.1 Site selection
lSelect a safe site to install the tower.
lThe distance between any power lines and the installation site should be at least one and
one-half times the height of the tower. Make the distance even greater, if possible. Since
all overhead lines look somewhat alike, consider them all dangerous and stay well away
from them.
lIf there are power lines or buried utilities in the area, call the local utility providers for
assistance.
2.2 Tower mounting
lNEVER work alone; always have someone near who can summon help.
lCertain clothing may provide a degree of safety, but do not depend on it alone to preserve
life (for example, rubber boots or shoes, industrial rubber gloves, or a long shirt or jacket).
lCheck local weather conditions. Be sure it has not rained recently, and the ground is not
wet or muddy. Make sure rain or thunderstorms are not predicted for the day the tower is
to be installed.
UT20 and UT30 Universal Towers 1

lTo avoid having the tower being blown into nearby power lines, do not install or remove
towers in moderate or heavy winds.
lIf it is necessary to use a ladder, choose a ladder made of non-conductive, non-metallic
materials.
lHave someone present who has been trained in electric shock first aid, if possible.
2.3 Tower installation
lProperly assemble the tower according to the instructions in this manual (do this in the
location the tower is to be installed).
lOnce the tower is in its full vertical position, securely fasten the tower to the base.
lGround the tower in accordance with all applicable local electrical codes.
lKeep the bottom of the tower legs free of soil, ice, and debris to prevent trapping any
moisture inside or around the tower legs.
3. Initial inspection
3.1 Indoors
Immediately upon receipt of the tower:
lInspect the shipping cartons for visible damage. Report any damage to the shipping
company.
lOpen all shipping cartons.
lCheck the contents of the cartons against the invoice. Contact Campbell Scientific
immediately if any parts are missing.
3.2 Outdoors
lLocate a suitable site for the tower (Siting and exposure (p. 3)).
lPrepare the tower base (Tower installation (p. 9)).
oInstall sensors to be mounted above a height of 3 m.
oRaise the tower (Tower installation (p. 9)).
UT20 and UT30 Universal Towers 2

oInstall the instrumentation enclosure (Tower installation (p. 9)).
oInstall sensors to be mounted below a height of 3 m.
3.3 Tools required
Tools required to install and maintain a Campbell Scientific tower:
lShovel
lRake
lOpen end wrenches: 3/8 in, 7/16 in, 1/2 in, (2) 9/16 in
lSocket wrench set
lMagnetic compass
lTape measure
lNut driver (3/8 in)
lLevel
lSledgehammer
lPliers
lStraight bit screwdrivers
lPhillips screwdrivers
4. Siting and exposure
DANGER:
If any part of the weather station comes into contact with power lines, death or serious injury
could occur. Contact local utilities for the location of buried utility lines before digging or
driving ground rods.
Selecting an appropriate site for the weather station is critical to obtain accurate meteorological
data. In general, the site should be representative of the area being studied, and away from the
influence of obstructions such as buildings and trees.
Do not place the weather station where sprinkler irrigation water will strike the sensors or
instrument enclosure.
The general guidelines for site selection given here were condensed from these sources: EPA
(2000)1, WMO (2010)2, and AASC (1985)3.
UT20 and UT30 Universal Towers 3

4.1 Wind speed and direction
As specified by the EPA1, wind sensors should be located over open, level terrain at a distance at
least ten times the height of any nearby buildings, trees, or other obstructions as shown in
FIGURE 4-1 (p. 4).
Standard measurement heights:
l3.0 m ± 0.1 m recommended (AASC)
l2.0 m ± 0.1 m, 10.0 m ± 0.5 m optional (AASC)
l10.0 m (WMO and EPA)
FIGURE 4-1. Effect of a structure on wind flow
4.2 Temperature and relative humidity
Sensors should be located over an open, level area at least 9 m (EPA1) in diameter. The surface
should be covered by short grass, or, where grass does not grow, the natural earth surface. Locate
sensors at a distance of at least four times the height of any nearby obstructions and at least 30 m
(EPA1) from paved areas. Sensors must be protected from thermal radiation and adequately
ventilated.
UT20 and UT30 Universal Towers 4

Situations to avoid include:
lIndustrial heat sources
lRooftops
lSteep slopes
lSheltered hollows
lTall vegetation
lShaded areas
lSwamps
lAreas where snow drifts occur
lLow places holding standing water after rainstorms
Standard measurement heights:
l1.5 m ± 1.0 m (AASC)
l1.25 to 2.00 m (WMO)
l2.0 m temperature (EPA)
l2.0 m and 10.0 m for temperature difference (EPA)
4.3 Precipitation
Rain gages must be sited on level ground covered with short grass or gravel. In open areas,
choose a site where the distance to any obstruction is two to four times (EPA, AASC) the height
of the obstruction.
Position the height of the opening as low as possible, but high enough to avoid splashing from
the ground. Wind shields, such as Campbell Scientific 260 953 Alter-Type Rain Gage Wind
Screen, are recommended for open areas.
When necessary, use heated collectors to properly measure frozen precipitation. The gage must
be mounted above the average level of snow accumulation in areas that experience significant
snowfall.
Standard measurement heights:
l1.0 m ± 1.0 cm (AASC)
l30.0 cm minimum (WMO, EPA)
4.4 Solar radiation
Mount pyranometers in locations that avoid shadows on the sensor at any time. Mounting the
sensor on the southernmost (Northern Hemisphere) portion of the weather station will minimize
UT20 and UT30 Universal Towers 5

the chance of shading from other weather station structures. Reflective surfaces and sources of
artificial radiation must be avoided.
Heated pyranometers, such as the SP230-L from Campbell Scientific, are available for use in areas
where snow, frost, or dew may accumulate.
The height the sensor is mounted is not critical.
4.5 Soil temperature
Prepare a site for soil temperature measurements at least 1 m2 and typical of the surface of
interest. The ground surface must be level to the immediate area (10 m radius).
Standard measurement depths:
l10 cm ± 1.0 cm (AASC)
l5.0 cm, 10.0 cm, 50.0 cm, 100.0 cm (WMO)
4.6 Siting references
1EPA, (2000). Meteorological Monitoring Guidance for Regulatory Modeling Applications, DPA-
454/R-99-005. Office of Air Quality Planning and Standards, Research Triangle park, NC. 27711
2WMO, (2008 edition, updated in 2010). Guide to Meteorological Instruments and Methods of
observation. World Meteorological Organization No 8, 2008 edition, Geneva Switzerland.
3The State Climatologist, (1985). Publication of the American Association of State Climatologists:
Height and Exposure Standards for Sensors on Automated Weather Stations, v. 9, No. 4, October
1985.
5. Overview
The UT20 and UT30 towers provide a versatile mount for sensors, antennas, solar panels,
environmental enclosures, radiation shields, and mounting crossarms. Its 6 m (20 ft) or 9 m (30 ft)
height allows for wind measurements at those levels.
The main tower frame (FIGURE 5-1 (p. 7)) is built from 2.5 cm (1 in) OD (outside diameter)
corrosion-resistant aluminum tubing. It includes an adjustable mast, a hinged base, anchor bolts,
lightning rod, ground rod, and cable tie kit.
Enclosures purchased for use with this tower must be ordered with the tower mount option. This
provides the necessary bracketing to mount the enclosure to the tower.
UT20 and UT30 Universal Towers 6

FIGURE 5-1. UT20 tower
UT20 and UT30 Universal Towers 7

6. Specifications
UT20 UT30
Measurement height 6 m (20 ft) 10 m (30 ft)
Shipping weight 23 kg (50 lb) 29 kg (65 lb)
Material Hardened drawn 6063-T832 Aluminum
Top tower section 3 m tube OD
(outside diameter) 2.5 cm (1 in) 2.5 cm (1 in)
Top tower section 3 m width (center
of tubing to center of tubing) 33.3 cm (13.1 in) 25.7 cm (10.1 in)
Center tower section 3 m tube OD n/a 2.5 cm (1 in)
Center tower section 3 m width
(center of tubing to center of tubing) n/a 33.3 cm (13.1 in)
Bottom tower section 3 m tube OD 3.175cm(1.25in) 2.175cm(1.25in)
Bottom tower section 3 m width
(center of tubing to center of tubing) 43.2 cm (17 in) 43.2 cm (17 in)
Vertical pipe OD 2.5 cm (1 in)
Cross support pipe OD 0.953 cm (0.375 in)
Guyed tower area requirements ~3.5m(11.5ft)radius ~5m(17ft)radius
Required concrete pad dimensions
for UTBASE concrete mounting base
(note 1)
91 L x 91 W x 122 D cm
(36 x 36 x 48 in)
Maximum wind load
recommendations
(note 2)
177 km/h (110 mph) for gusts (UTBASE base, unguyed)
177 km/h (110 mph) for gusts (RBM18 base with/UTGUY)
Notes:
1. The concrete pad requirements assume heavy soil. Light, shifting, or sandy soils require a
bigger concrete pad.
UT20 and UT30 Universal Towers 8

2. The recommended wind load assumes proper installation, proper anchoring, and total
instrument projected area of less than two square feet. For the RFM18 base, the wind load
recommendation also assumes that the UTGUY turnbuckles are preloaded to equalize
tension, and the tower is guyed at a 60-degree angle relative to the ground (maximum).
The amount of wind load that these towers can withstand is affected by quality of
anchoring and installation, guy wire tension, soil type, guy angle, and the number, type,
and location of instruments fastened to the tower.
3. The UT30 is Universal Towers model #9-30. A more detailed drawing of this tower is
available at www.universaltowers.com.
7. Tower installation
7.1 Installing the tower
The tower provides a support structure for mounting the weather station components. FIGURE 7-
1(p. 9) shows a typical tower equipped with an instrumentation enclosure, meteorological
sensors, and a solar panel.
FIGURE 7-1. Weather tower
UT20 and UT30 Universal Towers 9

7.1.1 Base and Guy Anchor Layout
The tower attaches to a user-supplied concrete foundation as shown in FIGURE 7-1 (p. 9). The
base brackets, anchor bolts, and nuts are included with the tower.
A guyed UT20 tower requires an area approximately 11.5 ft in radius, and a guyed UT30 tower
requires an area approximately 17 ft in radius. Brush and tall weeds need to be removed.
Otherwise, the natural vegetation and ground surface should be disturbed as little as possible.
Drive a stake where the base of the tower will be located. Attach a line to the stake and scribe a
circle with an 11.5 ft radius for the UT20 or a 17 ft radius for the UT30. The tower will be
positioned so two legs will be parallel to the equator as well as closest to the equator. The tower
will then tilt away from the equator at an angle for servicing as shown by the two tilt direction
options in FIGURE 7-2 (p. 11). Drive a stake on the scribed line opposite the direction the tower
will hinge for the first guy anchor location.
When using a UT30 on level ground, lay out the remaining two anchor locations by measuring
29.5 ft from the first anchor to the scribed line on either side of the base stake (FIGURE 7-2 (p.
11)). When using a UT20 on level ground, lay out the two remaining anchor locations 20 ft from
the first anchor to the scribed line on either side of the base stake.
UT20 and UT30 Universal Towers 10

FIGURE 7-2. Guy anchor locations on level ground
On unlevel ground, use a compass at the base stake to lay out the remaining two anchor
locations 120 degrees from the first. Vary the distance between the tower and each anchor so that
the angle between the tower and the guy wire will be approximately 30 degrees.
7.1.2 Tower base installation
There are two base options: the UTBASE base is poured in concrete; the RFM18 roof mount base
is anchored to a flat surface.
7.1.2.1 UTBASE base installation
For the wood frames, the following parts are needed:
l38 x 89 mm (2 x 4) lumber of the following lengths:
oTwo 152.4 cm (60 in)
oTwo 91.4 cm (36 in)
oOne 109.2 cm (43 in)
oTwo 25.4 cm (10 in)
UT20 and UT30 Universal Towers 11

l70 mm (2.5 in) wood or deck screws
l25 mm (1 in) wood screws
1. Dig a hole 0.9 m (36 in) square and 1.2 m (48 in) deep where the tower base will be located.
2. Construct a concrete form out of 38 x 89 mm (2 x 4) lumber, 0.9 m (36 in) square (inside
dimensions) as shown in FIGURE 7-3 (p. 12). Center the form over the hole and drive two
wooden stakes along the outside edge of each side (FIGURE 7-4 (p. 13)). Level the form
using a torpedo level and secure it in position by driving 65mm (21/2in) screws through
the stakes and into the form.
FIGURE 7-3. Concrete form and template frame dimensions
UT20 and UT30 Universal Towers 12

FIGURE 7-4. Concrete form staked in place
3. Assemble the template and anchor bolts as shown in FIGURE 7-5 (p. 14). If the metal
template was not purchased, refer to UTBASE paper template (p. 37) for instructions on
printing a paper pattern used to make a wooden template.
UT20 and UT30 Universal Towers 13

FIGURE 7-5. Template assembly
4. Assemble the template frame as shown in FIGURE 7-3 (p. 12). Align the template frame with
the notches in the template as shown in FIGURE 7-6 (p. 15) and secure the template to the
template frame with 25 mm (1 in) screws. Orient the template so one side of the tower faces
the equator. Set the template frame on top of the concrete form and position it so the
distance from the inside edge of the form to the three anchor bolts matches the
dimensions given in FIGURE 7-6 (p. 15). This placement optimizes the position of the
anchor bolts inside the concrete. Anchor the template frame to the concrete form with 65
mm (2 1/2 in) screws.
UT20 and UT30 Universal Towers 14

FIGURE 7-6. Template placement
5. Adjust the placement of the template on the anchor bolts to ensure there is 4.4 cm (1.75 in)
clearance for the end of the anchor bolt once the concrete has been poured (FIGURE 7-7
(p. 16)). Adjust the bolt position in the template until the correct clearance is set. Wrap the
visible threads at the top of each anchor bolt with masking tape to keep the threads clean
as the concrete is poured.
UT20 and UT30 Universal Towers 15

FIGURE 7-7. Anchor bolt height
NOTE:
To ensure proper anchoring of the anchor bolts in the concrete, it is recommended the
anchor bolts be secured in place prior to the concrete pour. Placing the anchor bolts
after the pour may result in voids and weak adhesion, allowing the anchor bolts to
move after the concrete has set. Loose-fitting anchor bolts will impact the integrity of a
freestanding tower system.
6. Fill the hole with concrete (FIGURE 7-8 (p. 17)). Remove the masking tape from the anchor
bolt threads once the concrete has been leveled. Allow three to four days for the concrete
to cure.
UT20 and UT30 Universal Towers 16

FIGURE 7-8. Template frame placement
7. Remove the screws that secure the template frame to the concrete form. Remove the top
nylon nut from each anchor bolt, then lift the template and template frame off the anchor
bolts. Remove the remaining nylon nuts from the anchor bolts.
8. Apply the anti-seize lubricant included with the anchor bolts to the threads on each anchor
bolt. Thread a clevis onto each anchor bolt until three threads of each anchor bolt are
visible inside each clevis. Angle the clevises in the same direction to allow the tower to tilt
away from the equator as shown in FIGURE 7-9 (p. 18). Leg 1 will be one of the two legs
along the side aimed at the equator. This positioning allows a solar panel to be attached to
two tower legs while providing easy access to sensors at the top of the tower.
UT20 and UT30 Universal Towers 17