EIJKELKAMP QUICK DRAW 2900F1 User manual

INSTRUCTIONS
OPERATING
Model 2900F1 “QUICK DRAW” SOILMOISTURE PROBE December 2009
The 14.04.05 QuickDraw Soilmoisture Probe is the most effective portable moisture measuring
instrument available. Designed for rugged eld use, the patented construction utilizing capil-
lary tube connections and a super porous ceramic tip assures fast response and accurate
readings, independent of temperature differences. The self-servicing feature, unique in tensi-
ometer construction, eliminates the need for accessory service kits, and assures fast response
times after years of use.
The Probe is shipped in a dry condition for greater convenience in handling and storage over a
period of time. Follow the simple instructions to water ll your unit in preparation for use.
(Figure 1) - 14.04.05 Soilmoisture "Quick Draw" Probe
P.O. Box 4, 6987 ZG Giesbeek
Nijverheidsstraat 30,
6987 EM Giesbeek,
The Netherlands
T+31 313 880200
F+31 313 880299
E[email protected]
Ihttp://www.eijkelkamp.com
M1.14.04.05.E
14.04.05

2
TABLE OF CONTENTS
Table of Contents.................................................................................................Page 2
Unpacking............................................................................................................Page 3
Cautions & Warnings...........................................................................................Page 3
Warranty & Liability..............................................................................,,,.............Page 3
Aquaint Yourself With The Parts..........................................................................Page 4
Theory of Operation............................................................................................Page 5
Venting and Adjusting Dial Gauge.......................................................................Page 6
Requirements Prior to Use / Initial Filling............................................................Page 7
Installation...........................................................................................................Page 11
Making a Soil Moisture Measurement.....................................................Page 11
Dial Gauge Pressure Build-up.................................................................Page 14
Irrigation Schedualing.............................................................................Page 15
Routine Measurements...........................................................................Page 16
Troubleshooting..................................................................................................Page 17
Replacing the Ceramic Tip..................................................................................Page 18
Replacing the Dial Gauge...................................................................................Page 20
Time Required to make a Reading.....................................................................Page 22
Tips for Scheduling Irrigations............................................................................Page 23
Care and Maintenance.......................................................................................Page 25
Parts List.............................................................................................................Page 27

Eijkelkamp Agrisearch Equipment (EAE)warrants all products manufactured by EAE to be free from
defects in materials and workmanship under normal use and service for twelve (12) months
from the date of invoice provided the section below has been met.
Eijkelkamp (EAE) is not liable for any damages, actual or inferred, caused
by misuse or improper handling of its products. EAE products are designed to be used solely as
describedintheseproduct operatinginstructionsbyaprudentindividual under normaloperating
conditions in applications intended for use by this product.
WARRANTY & LIABILITY
UNPACKING
CAUTIONS & WARNINGS
The Soilmoisture "Quick Draw" Probe should be removed from the eld prior to the onset
of freezing conditions. Since the Probe is a water-lled system, it is essential that the unit
be stored and used at temperatures above freezing. Freezing temperatures, of course, will
cause the water within the unit to freeze and expand as ice is formed. This can cause break-
age of the ceramic tip and distort or rupture the thin-walled Bourdon tube within the dial
gauge.
If the Bourdon tube is ruptured, the dial gauge cannot be repaired and will have to be replaced.
If the Bourdon tube is distorted but not ruptured, it may be possible to reset the pointer on the
gauge to correct the change in calibration caused by freezing.
Intense heat can cause the plastic Carrying Case to distort and can result in the evaporation
of all water from the sponge within the Carrying Case. This will be detrimental to the opera-
tion of the Soilmoisture Probe. It will also result in frequent servicing for removal of air. Do
not subject the Soilmoisture Probe to intense heat while storing or transporting it. Very high
temperatures can develop within a closed cab of a truck or the trunk of a car.
Please see page for care and user tips.
Not Liable for improper use. Remove all packing materials and check the 2900F1 Soilmois-
ture "Quick Draw" Probe for any damage that may have occurred during shipment. If any
part of the Quick Draw is damaged, call the carrier immediately to report it. Keep the ship-
ping container and all evidence to support your claim.
Do not bump or drop the dial gauge or ceramic sensing tip or they could break and will need
to be replaced. Take care not to let the sensing tip come in contact with grease or any other
similar material that could clog the pores of the ceramic.
Please verify that your shipment is complete.
3

(Figure 2) - 2900K1 Parts
AQUAINT YOURSELF WITH THE PARTS
The Probe, Coring Tool, and Cleaning Rod are held in place by the molded plas-
tic retainers at the top of the Carrying Case.
NOTE: The Probe ts into the side of the Carrying Case that is marked “PROBE”
, and the Coring Tool ts into the other side of the Carrying Case that is marked
“CORING TOOL”. (Fig. 3).
It is very important to keep the Probe in the side of the Carrying Case marked
“PROBE” when it is not actually being inserted in the soil, because this side of
the Carrying Case has a water storage reservoir at the bottom. During the “Initial
Filling” operation, pictured and described on pages 7 through 10, you will ll
the water storage reservoir. Thereafter, the sensing tip of the Probe will be kept
moist.
An Accessory Kit is provided with each Probe. It consists of a small screwdriver,
a 3/32” Allen wrench, and a replacement sensing tip and seals. The screwdriver
is used to vent and adjust the dial gauge and to replace the sensing tip. TheAllen
wrench is used in the event the dial gauge needs replacement.
PROBE CORING
TOOL
CLEANING
ROD
PROBE
CASE
(Figure 3) - Probe case
Tool placement
DIAL GAUGE
NULL KNOB
POROUS CERAMIC
SENSING TIP
CLEANING RODCARRYING CASE PROBE CORING TOOL
4

55
THEORY OF OPERATION
The 14.04.05 Soilmoisture Probe is a tensiometer-type instrument that reads
soil suction directly. The “soil suction” reading is a direct measure of the availability
of moisture for plant growth, and the standard unit of measurement is the “bar”. The
bar* is a unit of pressure in the metric system and is used to dene positive pressure
(above atmospheric pressure), or negative pressure or vacuum (below atmospheric
pressure).
The gauge on the Probe is calibrated in hundredths of a bar (or centibars) of vacuum,
and is graduated from zero to 100.
In scientic work, it is becoming customary to express pressures and vacu-ums in a
unit of measure called a “Pascal”, and a “Kilopascal”, which is 1000 times as large as
a Pascal. A “centibar”, as used above, is exactly equal to a Kilopascal. Therefore, the
dial gauge on the Probe also reads in kilopascals and is graduated from zero to 100
kilopascals (KPa).
Soil suction is actually created by the attraction that each soil particle has for the
water in the soil. Because of this attraction, water forms a lm around each particle of
soil and collects in the capillary spaces between the soil particles. As the soil be-
comes drier, these lms become thinner and the attraction or soil suction increases.
The plant root has to over-come this soil suction, or attraction force, in order to
withdraw moisture from the soil. The measurement of soil suction then gives a direct
indication of the amount of work the plant root must do to get water from the soil. The
only moisture measuring instruments that accurately measure soil suction are those
using the tensiometer principle. These instruments read centibars of soil suction
directly without calibration for soil type, salinity, or temperature.
When the Probe is inserted into the cored hole, there are various effects associated
with the movement of the porous ceramic sensing tip through the soil. The soil sur-
rounding the tip is slightly compacted and the wiping action of the porous ceramic
through the soil causes small thermal effects. It takes a few moments for these dis-
turbances to disperse, and this is the reason that it is not desirable to move the Null
Knob for the rst minute after insertion of the Probe.
In order to obtain a soil suction reading, it is necessary for a small amount of water
to transfer between the sensing tip of the Probe and the soil. When the Null Knob is
turned clockwise, water is forced out of the Probe sensing tip and into the surround-
ing soil. When the Null Knob is turned counterclockwise, a vacuum is created within
the Probe, which causes moisture to move from the soil through the ceramic sens-
ing tip and into the Probe. In order to obtain an accurate reading within the minimum
amount of time, one must be careful not to disturb the moisture conditions surround-
ing the sensing tip.
Steps for initial filling
(before installation)
When examining the Probe, DO NOT leave the porous ceramic sensing tip exposed
to the air for prolonged periods. When the Probe is removed from the Carrying Case
and the sensing tip is not kept moist, evaporation of moisture from the tip will pull the
dial gauge up to a very high centibar reading. Under these conditions, air can dif-
fuse through the water in the pores of the sensing tip and enter the Probe, which can
result in a decrease in sensitivity and require a relling cycle.

Venting and Adjusting the Dial Gauge
The 2060FG dial gauge is hermetically sealed at the factory at sea level.
If you live at a higher elevation, the pointer on the dial gauge may read
higher than zero when you unpack it. This is due to the lower atmospheric
pressure at your elevation.
First, simply press the vent pin located, at the top of the gauge, to release
any collected air. Located on the face of the gage is an insertion point for
a small athead screwdriver. If the gauge is reading high, turn the screw-
driver clockwise an estimated amount to correct the error. If the gauge
reads low, turn the screwdriver counterclockwise an estimated amount to
correct the error. Repeat the process if necessary until the pointer is on
zero.
VENT PIN
EFFECTS OF ALTITUDE ON OPERATION OF THE PROBE
PRACTICAL READING RANGE
0 TO 85 CENTIBARS
IN THIS RANGE AIR COMING
OUT OF SOLUTION MAKES
READING INACURATE
THEORETICAL LIMIT
OF READING
AT SEA LEVEL
PRACTICAL READING RANGE
0 TO 81 CENTIBARS
IN THIS RANGE AIR COMING
OUT OF SOLUTION MAKES
READING INACURATE
THEORETICAL LIMIT
OF READING
IN THIS RANGE WATER
BREAKS INTO A VAPOR
CAUSING UNIT TO LOOSE
ALL OF ITS WATER
AT 1000 FT.
ABOVE SEA LEVEL
CENTIBARS OF SOIL
SUCTION
SOILMOISTURE EQUIPMENT CORP
Santa Barbara, CA USA
90
80
70 60 50 40
30
20
10
0
DRY
WET
100
D
O
N
O
T
F
R
E
E
Z
E
40*-.0*4563&
CENTIBARS OF SOIL
SUCTION
SOILMOISTURE EQUIPMENT CORP
Santa Barbara, CA USA
90
80
70 60 50 40
30
20
10
0
DRY
WET
100
D
O
N
O
T
F
R
E
E
Z
E
40*-.0*4563&
AT 5000 FT.
ABOVE SEA LEVEL
CENTIBARS OF SOIL
SUCTION
SOILMOISTURE EQUIPMENT CORP
Santa Barbara, CA USA
90
80
70 60 50 40
30
20
10
0
DRY
WET
100
D
O
N
O
T
F
R
E
E
Z
E
40*-.0*4563&
PRACTICAL READING RANGE
0 TO 68 CENTIBARS
IN THIS RANGE AIR COMING
OUT OF SOLUTION MAKES
READING INACURATE
THEORETICAL LIMIT
OF READING
IN THIS RANGE WATER
BREAKS INTO A VAPOR
CAUSING UNIT TO LOOSE
ALL OF ITS WATER
The Reading Range is Reduced Approximately 3.5 Centibars
for Each 1000 Ft. Increase in Elevation
(Figure 4) - Venting the gauge
(Figure 5) - Effects of Altitude
6

STEP 1
Turn Null Knob clockwise as far as it will go and then
insert the porous ceramic sensing tip in water.
STEP 2
Keep the sensing tip in water. Turn the Null Knob coun-
terclockwise until you just see the red ring.
On initial lling, the pointer will normally rise to a reading
of 40 to 50. Let the pointer drop to zero.
STEP 3
Keep the sensing tip in water. Continue to turn the Null
Knob slowly counterclockwise until it is loose and can be
removed.
REQUIREMENTS PRIOR TO USE / INITIAL FILLING
RED RING
(Figure 8)
(Figure 7)
(Figure 6)
7

STEP 4
Fill the handle with water. A teaspoon works well for this
operation. Water should be poured into the handle slowly
and carefully so that air bubbles are not trapped. If you
see a bubble clinging to the smooth wall or bottom of the
handle cavity, nudge it free with the sharp end of a pencil.
STEP 5
Screw the Null Knob completely back in the Handle, which
will push out excess water.
While you are doing this, water will ooze out through the
porous ceramic tip and drip off the end.
STEP 6
Turn the Null Knob clockwise as far as it will go.
REQUIREMENTS PRIOR TO USE / INITIAL FILLING (cont.)
(Figure 10)
(Figure 11)
(Figure 9)
8

STEP 7
Remove the tip from the water and dry it with Kleenex or simi-
lar absorbent tissue. The dial pointer will rise to a reading of
20 or 30 as moisture is pulled into the dry tissue.
STEP 8
Turn the Null Knob counterclockwise until you just see the
red ring. The pointer will normally rise to a reading of 80 or
90 centibars if you live at an elevation between sea level and
about 2000 ft. If you live at higher elevations, the maximum
reading will be somewhat lower. See page 14, which de-
scribes the effect of altitude on the operation of the Probe.
If the pointer does not rise it can mean that rough handling
has cracked the porous ceramic sensing tip. See section on
“Care and Maintenance” for corrective action.
STEP 9
Immerse the porous sensing tip again in water and wait until
the pointer drops to zero.
REQUIREMENTS PRIOR TO USE / INITIAL FILLING (cont.)
RED RING
(Figure 13)
(Figure 12)
(Figure 14)
9

STEP 10
Repeat Step 3, removing the Null Knob again while the sensing tip is in the
water. Repeat Steps 4, 5, and 6, again relling the handle with water. Insert
the Null Knob and turn it clockwise as far as it will go.
STEP 11
Check Response Time. To do this, wipe the Probe and porous ceramic tip
with absorbent tissue to remove all excess water. Turn the Null Knob until
the pointer reaches a reading of 50 on the dial. Now when you dip the sens-
ing tip in the water, the pointer will normally drop from a reading of 50 to 10
in approximately one second - the time that it takes to say “one, one thou-
sand”. The Probe is ready for use if the response time is approximately one
second.
STEP 12
Fill the Carrying Case tube, which is labeled “PROBE” with water and allow
it to stand for a minute or two (See Fig.15). This will ll the sponge cartridge
with water. Empty out excess water and insert the Probe. The sponge car-
tridge in the Carrying Case will now keep the porous ceramic sensing tip wet
so it is ready to use at any time in the eld. In the future, always keep the
Probe in the Carrying Case when not in use.
REQUIREMENTS PRIOR TO USE / INITIAL FILLING (cont.)
After initial lling, if the response time is considerably more than one second, it
usually indicates that an air bubble has been trapped in the handle. To correct this,
simply repeat Steps 8 and 9, then Steps 3, 4, 5, and 6. Again look into the handle
cavity after lling to see if there are any bubbles clinging to the internal wall. In the
event there are bubbles, simply nudge them loose with the sharp end of a pencil. Fill
the cavity in the handle to the top, replace the Null Knob, wipe it dry, and again check
the response time.
The pointer may have to be adjusted after the lling operation. First read the following
section concerning the Dial Gauge and then refer to the “Venting and Adjusting the
Dial Gauge” section for specic instructions for adjusting the dial gauge pointer.
When the Probe is in the Carrying Case and is held vertically, the pointer on the
dial gauge should read zero. You will note, however, that if the Carrying Case is
tipped horizontally, the pointer on the dial gauge will read below zero. This is caused
by the shift in weight of the water column within the Probe. For normal use, the dial
pointer is set at zero when the Probe is held vertically and only when the ceramic
sensing tip is immersed in water. For pointer setting instructions, see the “Care &
Maintenance” section.
Response time is too
long
About the Dial Gauge
and Carrying Case
(Figure 15)
10

STEP 1 - CORING A HOLE
The rst operation in taking a reading is to core a hole to
accept the Probe using the Coring Tool. The Coring Tool
is pushed vertically into the soil (Fig. 16). After reaching
the depth desired, the Coring Tool is removed.
This operation will pull out the soil core and provide a
proper sized hole for insertion of the Probe.
The soil should be cleaned from the coring tool after
each coring operation to make sure that the succeed-
ing core will be properly cut. Remove the core by
inverting the coring tool so the core can slip out of the
handle end. The core itself gives a good prole of the
soil below the surface. The Cleaning Rod can be used
to remove any remaining soil from the cutting tip, as
shown in Fig. 17. In the event the soil becomes lodged
inside the Coring Tool, strike the side of the steel Cor-
ing Tool with the side of the Cleaning Rod to jar the soil
inside loose.
If an impediment is encountered, such as a rock or
hard root , when coring the hole simply move to an ad-
jacent location and core another hole. After the reading
has been made, no attempt should be made to plug
the hole, since the small hole is not detrimental and will
provide desirable aeration.
INSTALLATION / MAKING A SOIL MOISTURE MEASUREMENT
The Coring Tool makes a hole in the soil, which is
tapered at the bottom. The larger portion of the hole
provides clearance for the Probe when it is inserted
into the hole until it reaches the proper depth for
measurement. When the sensing tip of the Probe
reaches the bottom of the hole, push it rmly into
the tapered portion of the hole so a tight contact is
made between the sensing tip and the soil. This tight
contact is essential to make a good, fast soil suction
measurement (see Fig. 18).
The Coring Tool is made from strong, chromemoly
steel, and will withstand considerable punishment. If
the soil surface is too hard or dry for the Coring Tool
to penetrate, the surface soil can be broken with a
larger soil sampling tool or shovel. The Coring Tool
can then be pushed into the hole created to provide a
properly sized hole to accept the Probe.
In loose, cultivated soils and planting mixes, the
Probe can frequently be pushed directly into the soil
without coring a hole. When taking measurements
in these loose soils make sure the porous ceramic
sensing tip is in good contact with the soil and the
Probe is inserted without using undue force.
(Figure 17)
(Figure 16)
11

FIRST: TURN CLOCKWISE ALL THE WAY
SECOND: TURN COUNTER-CLOCKWISE
ONE HALF TURN
CORING TOOL
PUSHED INTO SOIL
“TAPERED” HOLE
MADE IN SOIL
LARGE PORTION
OF HOLE PROVIDES
CLEARANCE FOR PROBE
“TAPERED” PORTION OF
HOLE ASSURES TIGHT
FIT BETWEEN SENSING
TIP AND SOIL
STEP 2 - INSERTING THE PROBE
Prior to removing the Probe from the Carrying Case,
turn the Null Knob clockwise as far as it will go and
then undo the knob (counterclockwise) approximately
1/2 turn. This operation will provide the proper range
for the Null Knob when taking a reading (see Fig. 19).
Next, remove the Probe from the Carrying Case and
insert it into the hole made by the Coring Tool. Push it
in so the sensing tip is in rm contact with the soil. (see
Fig.20).
NOTE: If the Probe has been stored in a very hot envi-
ronment such as the back of a truck, you should leave
the Probe in the initially cored hole for two to three
minutes to bring the Probe to approximate temperature
equilibrium with the soil. The Model 2900F Probe has
been designed to have very minimum temperature
effects. However, it is desirable to eliminate extreme
temperature variations be-tween the soil and the Probe
in order to obtain the fastest response and ease of use.
After the initial temperature adjustment, when neces-
sary return the Probe to the Carrying Case to drop the
pointer reading to zero. Then core an adjacent hole
and re-insert the Probe.
If the soil is saturated with water, the pointer of the dial
gauge will remain at zero. Otherwise, the pointer will
immediately start to rise when the Probe is inserted
into the hole. After insertion, allow the Probe to remain
undisturbed for approximately one minute. At the end
of one minute, observe the pointer reading.
MAKING A SOIL MOISTURE MEASUREMENT (cont.)
(Figure 18)
(Figure 19)
12

If, after the rst adjustment, the pointer continues to move up to a higher rather than a lower reading, you should
immediately move the pointer approximately 10 centibars higher and observe the pointer movement. If it contin-
ues to move up to a higher value, advance the pointer an additional 10 centibars. Once you reach a level where
the pointer starts to move back down, you have “bracketed” the reading, and adjustments can be made, as de-
scribed above, to arrive at the correct value.
In many moist soils, the Probe will come to equilibrium very quickly without any appreciable adjustment of the Null
Knob.
Through experience in using the Probe in your soils, you will soon be able to estimate the nal dial gauge reading
by the speed the pointer moves after insertion of the Probe. It is best to minimize the use of the Null Knob to limit
disturbing the soil moisture conditions being measured.
After making a reading, the Soilmoisture Probe should be wiped free of surplus clinging soil and immediately
returned to the Carrying Case so the sensing tip remains moist by being in contact with the water storage sponge,
with the dial gauge reading zero. When making eld measurements, if the soil suction value exceeds the highest
operating value corresponding to your elevation, the Probe should not be left in the soil for extended periods.
Soil moisture values can vary considerably within a given area because of differences in root action, drainage and
exposure. For this reason, it is desirable to make several readings in a given area in order to fully evaluate the soil
moisture conditions.
Turn the Null Knob counterclockwise to bring the pointer
up to a value, which is one and one-half times the initial
reading after the one-minute period. In other words, if the
reading after one minute is 20 centibars, turn the Probe so
the reading is adjusted to 30 centibars. If the reading is 40
centibars, turn the Null Knob so the pointer is at 60 cen-
tibars, etc.
After making the rst adjustment, observe the pointer
movement after 15 to 30 seconds. Tapping the dial gauge
lightly with your nger while observing the pointer move-
ment will tend to reduce the normal internal friction so
changes in the pointer position can be observed with mini-
mum lapsed time. If the pointer is moving down to a lower
value than the one set, you know that the correct soil suc-
tion value is somewhere between the initial reading at one
minute and the adjusted value. In this case, turn the Null
Knob in a clockwise direction to lower the pointer to read
half way between the initial value and the rst set value.
After this second adjustment, again observe the direction in
which the pointer is moving and then make a sub-sequent
adjustment to an intermediate value. This process “brack-
ets” the actual soil suction value, and you can very quickly
adjust the Probe to the true soil suction value. When the
pointer is adjusted to the true soil suction value, it will not
move up or down, but will remain in a xed position.
MAKING A SOIL MOISTURE MEASUREMENT (cont.)
(Figure 20)
13

It has been our experience that accurate, reliable moisture readings can be made
within a few minutes at any one given location. In general, the readings can be made
more quickly when soil suction levels are in the low range than when they are in the
high range.
No problems in measurement will be encountered in sandy or sandy-loam soils. In
the event you are making measurements in extremely heavy clay soils, more time
than normal will be required to reach equilibrium because of the extremely slow
movement of water through this type of soil.
CAUTION
In wet clay soils, the plastic soil itself can make an airtight closure around the sensing
tip as the Probe is being pushed into the soil. If this happens, pressure can be built
up in the Probe by the air trapped in front of the Probe, see Fig. 39. Since this air is
sealed by the wet clay soil, a high air pressure can develop as the Probe is pushed
further and further into the soil.
To detect such a condition, observe the dial pointer when pushing the Probe down
into the soil. If the pointer moves below the zero mark and touches the pin, pressure
is building up. See Fig. 40. Stop pushing and pull the Probe up to relieve the pres-
sure. Then push the Probe down and pull up again in short strokes to enlarge the
hole in the sensing tip area, which will prevent the entrapment of air. Then push the
Probe to full depth and make a reading.
DIAL GAUGE
PRESSURE BUILD-UP
CAUTION!
MAKING A SOIL MOISTURE MEASUREMENT (cont.)
(Figure 21)
CENTIBARS OF SOIL
SUCTION
SOILMOISTURE EQUIPMENT CORP
Santa Barbara, CA USA
90
80
70 60 50 40
30
20
10
0
DRY
WET
100
D
O
N
O
T
F
R
E
E
Z
E
SOILMOISTURE
PIN DIAL GAUGE
PRESSURE
BUILD UP
14

ZERO:
0-10 CENTIBARS:
10-20 CENTIBARS:
20-40 CENTIBARS:
40-60 CENTIBARS:
60-80 CENTIBARS:
CENTIBARS OF SOIL
SUCTION
SOILMOISTURE EQUIPMENT CORP
Santa Barbara, CA USA
90
80
70 60 50 40
30
20
10
0
DRY
WET
100
D
O
N
O
T
F
R
E
E
Z
E
SOILMOISTURE
CENTIBARS OF SOIL
SUCTION
SOILMOISTURE EQUIPMENT CORP
Santa Barbara, CA USA
90
80
70 60 50 40
30
20
DRY
WET
100
10
0
D
O
N
O
T
F
R
E
E
Z
E
SOILMOISTURE
CENTIBARS OF SOIL
SUCTION
SOILMOISTURE EQUIPMENT CORP
Santa Barbara, CA USA
90
80
70 60 50 40
30
20
DRY
WET
100
10
0
D
O
N
O
T
F
R
E
E
Z
E
SOILMOISTURE
CENTIBARS OF SOIL
SUCTION
SOILMOISTURE EQUIPMENT CORP
Santa Barbara, CA USA
90
80
70 60 50 40
30
20
DRY
WET
100
10
0
D
O
N
O
T
F
R
E
E
Z
E
SOILMOISTURE
CENTIBARS OF SOIL
SUCTION
SOILMOISTURE EQUIPMENT CORP
Santa Barbara, CA USA
90
80
70 60 50 40
30
20
DRY
WET
100
10
0
D
O
N
O
T
F
R
E
E
Z
E
SOILMOISTURE
CENTIBARS OF SOIL
SUCTION
SOILMOISTURE EQUIPMENT CORP
Santa Barbara, CA USA
90
80
70 60 50 40
30
20
DRY
WET
100
10
0
D
O
N
O
T
F
R
E
E
Z
E
SOILMOISTURE
A gauge reading of zero means the
surrounding soil is completely saturated
with water, regardless of the type of soil.
Zero readings can be expected after a
heavy rain or deep irrigation. If the zero
reading persists after a long
period of time, there will be oxygen
starvation to plant roots and develop-
ment of diseases. A persistent zero
reading after irrigation indicates poor
drainage conditions which should be
investigated and corrected.
Gauge readings in the range of 0-10cb
indicated a surplus of water for plant
growth. Water held by the soil in this
range drains off within a few days.
Persistent readings in this range
indicate poor drainage conditions
which should be corrected to obtain
healthy plant growth.
Gauge readings in the range of 10-20cb
indicate that there is ample moisture
and also air in the soil for healthy plant
growth in all types of soils. This range is
often referred to as the “field capacity”
range for soils, which means that the
soil has reached its “capacity” and
cannot hold anymore water for future
plant growth. When soils are at “field
capacity”, any additional water that is
added drains out of the root zone within
a day or two—before it can be used by
the growing plant. If irrigation has been
in process, it should be stopped when
gauge drops to this level, since any
further additional water will be quickly
drained from the root zone and wasted,
carrying with it valuable fertilizer.
Available moisture and aeration good
for plant growth.
HEAVY CLAY SOILS: No irrigation
required.
MEDIUM TEXTURED SOILS: No
irrigation required.
SANDY SOILS: Irrigation started for
coarser sandy soils in the 20-30 cb
range. For finer sandy soils in the
30-40 cb range.
Available moisture and aeration are
good for plant growth in finer textured
soils.
HEAVY CLAY SOILS: No irrigation
required.
MEDIUM TEXTURED SOILS: Irriga-
tion started in this range. The finer the
texture the higher the reading before
start of irrigation.
SANDY SOILS: Too dry. Hot windy
conditions can force soil suction to
high reading quickly and damage
plants.
Readily available moisture scarce,
except in heavy clay soils.
HEAVY CLAY SOILS: Start of irriga-
tion desirable as soil suction values
reach 70-80 cb.
MEDIUM TEXTURED SOILS: Too
dry. Hot, windy conditions can force
soil suction to high reading quickly
and damage plants.
SANDY SOILS: Too dry. Damage to
plants will occur before irrigation can
be applied.
GAUGE READINGS / IRRIGATION SCHEDUALING
15

The QuickDraw can be used for different types of measurements; for spot checks and measures from
a permanent location:
a) Use for spot checks to determine the wetting area from drippers or to determine if there is enough
moisture for germination in the seed-bed. Simply use the coring tool to shape the hole at the depth of
measurement. Insert the QuickDraw and wait for the reading to become steady.
b) One can make routine measurements at a given depth in the same hole each time measurements
are necessary. Use ½” PVC as a riser from the depth to measure to the soil surface. Place the pipe at
the depth of measurement , minus an inch or so. Use an end cap or aluminum foil to prevent irrigation
from a sprinkler from entering the pipe and wetting the soil at depth instead of from surface inltration.
Remove the cap and insert the QuickDraw and force the ceramic tip into the soil at the depth of mea-
surement. Make your measurement as normal. Re-cap the riser pipe when nished.
Use the null knob to adjust the vacuum in the tensiometer to your set point for irrigation particular to
the soil and crop being monitoring. The advantage of adjusting the null knob is to quickly determine if
the set point has been reached or not and the question … is it time to irrigate? Can be easily deter-
mined.
If the vacuum dial gauge exceeds the set point, then it is denitely time to schedule the irrigation. If
the vacuum dial gauge decreases in vacuum, then the soil is more moist than your set point for irriga-
tion and your decision is to not irrigate.
Using this approach, allows the user to rapidly make management decisions. Absolute, at equilibrium,
measurements are not required using this approach.
ROUTINE MEASUREMENTS
16

The successful operation of the 14.04.05 Soilmoisture Probe is due to its struc-
tural rigidity and the fact that the air has been almost completely removed from the
water and the internal structure of the Probe. For these reasons, any small amount of
movement of water through the porous ceramic sensing tip will result in a substantial
change of the vacuum level within the Probe. This very responsive action coupled
with the use of the Null Knob, results in only a small disturbance to the water lms in
the surrounding soil, which are being measured. Hence, accurate measurements of
soil suction can be made quickly.
If air is present in the unit, then a substantial amount of water must ow through the
wall of the porous ceramic sensing tip to change the vacuum level within the Probe.
The air within the Probe expands as the pressure is reduced (centibar reading in-
creased), which causes a larger amount of water to move in and out of the surround-
ing soil. The result is a less responsive movement of the pointer on the dial gauge, a
“spongy” action of the Null Knob, and a longer time to obtain an accurate soil mois-
ture measurement. The response time is dened as the time required for the dial
pointer to drop from 50 centibars to 10 centibars when the porous ceramic sensing tip
is plunged into a container of water.
Over a period of many months or years, the pores in the ceramic sensing tip have a
tendency to become clogged with deposits, which decreases the permeability of the
ceramic. Such clogging will, of course, slow down the response time of the Probe.
If the Probe has been carefully lled with water to remove all accumulated air, and
the response time is still in excess of 2 seconds, it is advisable to replace the porous
ceramic sensing tip with a new one.
If, at any time, the operation of the Probe appears to be “spongy” and excessive time
is required to make a soil suction reading, simply remove the Probe from the Carrying
Case. Wipe the porous sensing tip with an absorbent tissue and turn the Null Knob
so the pointer on the dial gauge registers 50 centibars. Then plunge the sensing tip
of the Probe into a container of water and note the time required for the pointer to
drop from 50 centibars to 10 centibars. If it is appreciably more than one second, it
indicates that there is air accumulated within the Probe. To remove the air from the
Probe and restore the fast response time, rell the Probe with water as described
under “Initial Filling”, page 2.
If the porous ceramic sensing tip as been cracked during use, it will permit air to enter
the system. A very ne crack not be readily observed. Usually under these circum-
stances, it is not possible to obtain a reading of 50 centibars to conduct the response
time test. If a dial reading of 50 centibars cannot be reached by drying the sensing tip
and turning the Null Knob, there is too much air in the system, and there may also be
a crack in the sensing tip. To replace the porous ceramic sensing tip, see the section
on this.
TROUBLESHOOTING
Substantial change in
the vacuum level
Lack of reponse from
gauge
50 centibars can not be
reached
17

If the porous ceramic sensing tip has been broken or
cracked during use or if the pores of the ceramic have
become clogged resulting in too long Probe response
time, it can be readily replaced with a new one. The “O”
ring seals must also be replaced when you replace the
ceramic sensing tip,.
To replace the sensing tip, rst remove the slotted cap
nut at the end of the Probe. Use a large screw-driver that
ts the slot in the cap nut, or the small pointer-adjusting
screwdriver can be used, by inserting the side of the
screwdriver in the slot in the nut, as shown in Fig. 22.
When facing the end of the Probe, turn the cap nut
COUNTERCLOCKWISE to loosen it. Completely remove
the cap nut, the porous ceramic sensing tip, and the two
“O” ring seals at either end of the sensing tip. When you
re-move the parts, be sure that the smooth surfaces on
the cap nut and on the stem of the Probe, where the “O”
rings seat, are not scratched or marred. It is essential
that these surfaces are kept smooth to assure a com-
plete vacuum seal when the new sensing tip is installed.
Clean off any accumulated corrosion from the stem of the
Probe.
Fig. 23 shows the stem of the Probe with the two small
cross holes. The “O” ring seals, porous ceramic sensing
tip and slotted cap nut are arranged in this photo in the
same manner as they t on to the stem of the Probe.
Figs. 24 through 28 show the successive operations in
mounting the parts on the stem of the Probe.
In the nal assembly operation, screw on the slot-ted cap
nut and tighten it securely with a screw-driver. The slotted
cap screw should be tightened as far as it will go. Parts
have been carefully machined so the “O” ring seals are
properly squeezed when the slotted cap nut is screwed
completely on until it seats on the end of the Probe stem.
The “O” rings make a vacuum-tight seal between the
brass surfaces of the Probe stem parts and the ends of
the porous ceramic sensing tip.
The ends of the porous ceramic sensing tip have been
machined smooth to assure a vacuum-tight seal. When
you mount the porous ceramic sensing
Replacing the Porous
Ceramic Sensing Tip
(Figure 22)
(Figure 23)
(Figure 24)
18

tip on the Probe, make sure that the sensing tip is not
scratched or chipped.
The Porous Ceramic Sensing Tip is supplied with a tapered
conguration. The taper matches the taper of the Coring
Tool. The taper assures better contact with the soil, which
increases sensitivity and speed of response.
When you replace the tip, special care must be taken to
see that the “top” arrow marked on the tip points in the
direction as shown in Fig. 29.
After replacing the tip, ll the Probe as described in “Initial
Filling”.
(Figure 25)
(Figure 26)
(Figure 27)
(Figure 28)
(Figure 29)
19

Replacing The Dial Gauge
If the dial gauge has been mechanically damaged making it
inoperative, it may be replaced in the eld.
First remove the socket head set screw from the handle,
as shown in Fig. 30. This is an “Allen” head set screw that
accepts a 3/32” size Allen wrench, which is supplied in the
Accessory Kit.
Then grasp the dial gauge rmly, as shown in Fig. 31, and
turn it counterclockwise until it is free from the handle.
Fig. 32 shows the dial gauge removed from the handle.
The internal connecting tube usually remains in the dial
gauge. Carefully pull out the internal connecting tube from the
dial gauge.
(Figure 30)
(Figure 31)
(Figure 32)
20