UGT UMP-2 User manual

Operating Manual
UMP-2
Version: 29/10/18
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UMP-2 combined soil humidity, conductivity and temperature
sensor

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Inhalt
1. Introduction.......................................................................................................................................3
2. General information ..........................................................................................................................5
2.1. Measuring principle of soil moisture sensors ..................................................................... 5
2.2. Schematic design of the UMP - 2........................................................................................ 6
2.3. Technical data ..................................................................................................................... 7
3. Mode of operation of the UMP - 2....................................................................................................8
3.1. Water content measurement ............................................................................................. 8
3.2. Electrical conductivity measurement.................................................................................. 8
3.3. Temperature measurement................................................................................................ 9
4. Installation.......................................................................................................................................10
4.1. Optimization of the measurement ................................................................................... 11
4.2. Data output ....................................................................................................................... 12

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1. Introduction
Thank you for choosing the UMP –2 sensor. This manual can help you understand the UMP -
2 features.
We designed this UMP –2 sensor as an innovative device for measuring combined soil
humidity, conductivity and temperature in soils.
The UMP-2 series offers a range of combination sensors supplying high quality
measurements at minimum effort. The combination of the three measured variables of
volumetric water content, electrical conductivity and temperature in one sensor means that
these combination sensors save money spent on procurement and time spent on installation
and servicing. In addition, soil disturbance is reduced because only one sensor has to be
installed in order to measure three soil properties.
In Addition to the cable based sensor, wireless UMP-2 are also available, designed for a
different usage:
UMP-2 →Connection to the data logger by cable
Data storage on the data logger, output via an interface on
laptop or remote data transmission
Particularly suitable for measurement stations with several
sensors for long-term measurements
UMP-2 BT →Data transmitted via Bluetooth
Data is recorded through the UMP-2 Smartphone app
Designed for direct in situ measurements to determine current
values in different measurement stations
UMP-2 BT Plus →Data storage on the sensor
Data is transmitted via Bluetooth on a laptop
Particularly suitable as single sensor for medium-term
measurements

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There are several ways to contact UGT if you ever need assistance with your product, have
any questions, or feedback.
Email:
[e-mail] or [email protected]
Phone:
+ 49 (0) 33432 –89 575
Fax:
+ 49 (0) 33432 –89 573
If contacting us by email or fax, please include as part of your message your instrument
serial number, your name, address, phone, and a description of your problem or question.
Please read these instructions before operating your UMP –2 sensor to ensure that it
performs to its full potential.

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2. General information
2.1. Measuring principle of soil moisture sensors
The water content is one of the most important characteristic variables in soil science. It is
used by agriculture as limit value and control variable for irrigation, by construction as limit
value for the ability to drive on ground, and in environmental and landscape protection both
as a decision criterion for planned measures and as an important indicator.
Since a direct determination of the water content by weighing is not possible in the field,
indirect procedures are deployed to determine the volumetric water content to obtain non-
destructive and continuous measurements in the field.
The volumetric water content is the ratio of water volume in the soil to total volume and is
calculated according to (1):
𝜃 = 𝑉
𝜔
𝑉𝑇
∙100%
(1)
where
𝜃
…
Volumetric water content
𝑉
𝜔
...
Volume of water
𝑉𝑇
…
Total volume

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2.2. Schematic design of the UMP - 2
The basic construction is the same for all UMP-2 variants (Fig. 1). The probe is waterproof
and can be completely buried for a depth or horizontal installation. It is made of plastic or
stainless steel, while the measuring rods (antennas) are always made of stainless steel.
Regular maintenance is not necessary. On request, the measuring rods can also be produced
in other lengths. In this case, the measuring frequency also changes.
Figure 1 schematic design of the UMP-2

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2.3. Technical data
Power requirement
6V … 24V DC
Power input
60 mA
Water content
Measurement range
0 … 100 % vol. water content
Accuracy
± 2%
Resolution
0.1 % vol. water content
Electrical conductivity
Measurement range
0.001 … 5mS/cm
Optional measurement extension to 40mS/cm
possible
Accuracy
1%
Resolution
Temperature
Measurement range
-40 … +60°C
Accuracy
± 0.5°C (across the entire temperature range)
Resolution
0.01°C
Interfaces
Digital
RS485
Analogue output
3 X 0 …1,5 V
Including 1.5 m cable with M12 sensor connector

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3. Mode of operation of the UMP - 2
3.1. Water content measurement
The water content measurement procedure of the UMP-2 sensor is can neither be fully
described as FDR nor TDR method.
The basic mode of operation however corresponds to the FDR process, because the sensor
operates with a continuous signal at constant frequency (120 MHz) and not with a pulse.
However phase shift instead of frequency change is used to calculate the measurement
reading.
The measuring line consists of two stainless steel rods (antennas) of 50 mm length and with
a diameter of 3 mm. These dimensions and the measurement frequency produce a
measurement volume of approximately 500 ml. Faults within the measurement volume such
as vessel walls, large air pockets or cables can influence the measurement result. A
continuous signal runs along the antennas in the ground. The waves of the signal running
back and forth are compared here. The dielectric constant εof the surrounding soil/water
mix is determined from the phase difference of the signals running back and forth. The
dielectric constant for pure water at 20°C is ε=80. Dry soil has an εof 2 to 5. The dielectric
constant of the soil/water mix lies between these two levels, and is higher the more water
there is in the soil.
Using the calculated dielectric constant, the volumetric soil water content is then
determined according to the Topp/Davis equation.
The εvalue can also be called up when making independent water content calculations using
other mathematical formulas.
3.2. Electrical conductivity measurement
The UMP-2 sensor records the electrical conductivity of the soil by means of an additional
circuit (IC) independently of the soil moisture measurement. This system offers two main
advantages. On the one hand an extremely precise measurement of conductivity is possible
using the components and measurement principle. On the other hand the independently
measured conductivity can be used to correct the calculated water content.
Electrical conductivity effects the measurement of the dielectric constant of the soil. With an
increased electrical conductivity, the dielectric constant increases, which leads to falsely
elevated water content readings. Using a formula to adjust to a higher conductivity prevents
an offset in soil water content.
In order to measure conductivity, the soil moisture measurement is interrupted for a short
period of time, and a signal in the kHz range transmitted over the antennae. The
corresponding IC measures the impedance of several different frequencies and averages the
results.

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3.3. Temperature measurement
The UMP-2 sensor measures the soil temperature using a third circuit. A stainless steel bolt
recessed between the probes transmits the temperature of the soil. Using this location, the
temperature is measured right next to water content and electrical conductivity
measurements in order have the same origin for all measured values. A timespan of 6
minutes should be allowed to achieve a reliable temperature measurement.
If the UMP-2 is placed on the surface in the ground, it is necessary to take into account that
sunlight and temperature fluctuations in the atmosphere have a falsifying influence on the
measurement of the temperature. This is mainly done by heating the housing, which
influences the sensor.
Attention!
For temperature measurements with the UMP-2 in long-term operation, the device must be
completely buried in the ground.

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4. Installation
To conduct the measurement, the sensor is
placed into the ground with the probe rods and
the metal bolt having tight contact to the soil.
Air-filled cavities between soil and steel rods
lead to distorted measurement results.
To simplify the installation and to protect the
antennas, it is advised to prepare the
installation site with the supplied punching tool.
The antennas of the punching tool are narrower
than those of the sensor which ensures better
contact between soil and rods. The sensors are
watertight and can be buried in the ground.
Caution!
The antennas must be completely inserted
into the ground because the soil moisture is
determined for the entire length of the
antennas.
After the installation, the UMP-2 is directly
connected to the data logger via an analogue
cable. The programming of the data logger is
usually done by specialized UGT staff.
If desired, the programming of the logger can
be adapted by the user on their own. Please see
the data-logger manual for detailed instructions
on that.
Using the RS485 interface the sensor can also
be approached digital and accordingly
embedded in bus systems.
The measurement is administrated and read
out directly via the data logger. A periodical
maintenance is not necessary. In case of values
going out of range, the condition and position
of the probe needs to be checked. Erosion,
cracking and mechanical forces on the sensor or
removing the by a third party can lead to
altered measurement values.

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4.1. Optimization of the measurement
Special importance needs to be taken prior to the installation:
•For the measurement the antennas need to be completely inserted into the soil.
•Gaps between antenna and soil must be avoided (for example by moving the sensor
subsequent to the installation).
•The antennas have to be parallel and undamaged. The correct position of the
antennas to each other is crucial for the accuracy of the measurement results.
•Be careful while pushing the antennas into the soil. In case of a high penetration
resistance avoid the use of more force but rather try to install the probe again at
another spot. For very rigid soil pre-drilling is advised.
•When installed, the sensor must not be moved. By doing that, the antennas could be
twisted or bend leading to inaccurate measurement values and damage of the
antennas.
•In order to measure the soil temperature accurately, the temperature sensor has to
be in contact with the soil for at least 6 minutes.

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4.2. Data output
The UMP-2 sensor has a cable connection (1.5m; M12 sensor connector; assembly possible
on customer request) in order to connect it to a data logger.
The sensor measures continuously; the energy is supplied by the data logger. The data is
transmitted and stored at the logger from where it can be retrieved via cable or sent to a PC
via a modem.
When combined with UGT loggers, the data is available as *.csv or *.txt file for further
editing.
Terminal assignment UMP-1
Colour
Function
Signal
Measurement range
rt
+12V
bl
GND
gn
RS485 B
ws
RS485 A
ge
Vol%
0..1V
0..100%
rs
EC (conductivity)
0..1V
0,001..5mS/cm
gr
Temp
0..1V
-40..60°C
bn
AGND