An Apparatus for Monitoring Sea Ice Thickness Based on Coplanar

Multi-Electrode Capacitance Sensor

Ling Zhang and Yinke Dou

College of Electric and Power Engineering, Taiyuan University of Technology,No.79 West Sree Yinze,Taiyuant,

shanxi,China

{zhangling,douyinke}@tyut.edu.cn

Keywords: Coplanar, Multi-electrode capacitance, Sea ice, Antarctic.

Abstract: This study describes an apparatus for in situ measurement of centimeter-accurate changes in the sea ice

thickness in Antarctica. The apparatus consists of a rod-shaped measurement sensor based on coplanar

multi-electrode capacitance sensing technology. In use, it is vertically installed into the sea ice to realize

automatic monitoring of increases in sea ice thickness. It is suitable for monitoring fixed measurement sites

on ice that are not deformed. The apparatus presented was tested on landfast ice and ice cap near China’s

Zhongshan Station (East Antarctica) for approximately 6 months during the austral autumn and winter. Data

on the coastal sea ice thickness at the Zhongshan Station for 6 months was obtained. An analysis of the data

verifies the reliability and accuracy of the apparatus for monitoring Antarctic sea ice. Application

experiments prove that the apparatus can realize the automatic monitoring of sea ice thickness on fixed sites

and provides a new method of monitoring sea ice thickness.

1 INTRODUCTION

Sea ice thickness directly affects the thermodynamic

interaction of the atmosphere and marine

environments. It has long been considered a key

indicator reflecting climate change in polar regions.

However, little is known about ice thickness

changes. Sea ice plays an important role in the

global radiation balance and global climate due to its

smooth surface and the accumulated snow thereon.

Moreover, continuous, real-time automatic

monitoring of ice thickness on fixed sites is a

difficult problem in ice thickness detection

technology. At present, four methods are mainly

employed in sea ice thickness observation. These

are, manual hole-drilling measurements, remote

sensing measurements, sonar measurements, and

airborne (ship) electromagnetic sensing

measurements.

Manual hole-drilling was the earliest ice

thickness measurement used. The method is highly

accurate, very reliable, and has been widely used.

However, it cannot realize fixed-site real-time

measurement. Moreover, it requires high labor

intensity and shows low efficiency. Thus, it is

merely used to make measurements at key points. In

addition, this method cannot be used during ice

forming and thawing periods for the sake of safety.

Remote sensing refers to the measurement of a

wide range of ice structures using measurement

devices carried by satellites Satellite remote

sensing contributes much to the monitoring of a

wide range of ice and is widely utilized. However,

due to the satellite’s altitude, picture resolution is

low. Therefore, this method can only be used to

obtain characteristic ice information on a large scale.

It is not capable of acquiring ice parameters on

medium and smaller scales. Furthermore, it is

relatively easily influenced by weather.

In sonar measurement, a high frequency

transducer is used to emit different forms of signals

and the time-delay between the reflected signals

from the ice-air and ice-water interfaces detected.

The ice thickness can then be calculated from the

time difference between the echo signals from the

two interfaces and the sound velocity in the ice in

the measurement area. This method shows the

optimum under-ice resolution and can avoid the

influence of ice properties. However, it is only able

to detect the ice thickness below the waterline of the

ice layer.

Airborne (ship) radar measurements began to be

used in sea ice observation in the middle 1980s. In

Zhang, L. and Dou, Y.

An Apparatus for Monitoring Sea Ice Thickness Based on Coplanar Multi-Electrode Capacitance Sensor.

In 3rd International Conference on Electromechanical Control Technology and Transportation (ICECTT 2018), pages 467-475

ISBN: 978-989-758-312-4

467

this method, the ice thickness is obtained by

analyzing electromagnetic echo signals and

calculating the distance between the upper and lower

surfaces of the ice. The main commercial products

used include the EM-31 ice and snow detector, etc.

The method can be directly applied in moving

situations and can collect a large amount of data in a

short period of time without damage to the ice.

Thus, the influences of summer and device

installation on the ice melting rate are reduced.

However, in this method, the contours or ‘ups and

downs’ of the ice surface are all included in the

bottom surface morphology.

The members of our team have developed a

fixed-site magnetostrictive sea ice thickness

measurement device. The device was adopted to

monitor the sea ice near Zhongshan Station for more

than half a year and is capable of monitoring sea ice

thickness to a precision of ±2 mm. Unfortunately,

due to certain factors, such as the inability of the

power supply used to provide the long-term,

unattended mechanical power the system requires,

the equipment is still at present in a state of

improvement. Therefore, a new device is designed

in the current study to measure changes in the

snow/ice thickness at fixed sites. It aims to monitor

the sea ice thickness in time to a precision of 1 cm.

Moreover, the power consumption of its power

supply is low. A 12 V spirally-wound lead acid

battery with a capacity of 80 Ah can ensure normal

working of the whole device set for one year. In

addition, the whole device set has a low cost and is

suitable for being laid on a large area of sea ice. This

device was applied to the ice surface and ice cap

near Zhongshan Station.

This study first introduces the basic principles

involved, as well as the design and production

process used to construct the system for ice

thickness detection by coplanar multi-electrode

capacitance sensors and corresponding system.

Then, it discusses application of this apparatus in the

detection tests carried out on the sea ice near

Zhongshan Station. The accuracy of the apparatus is

also analyzed. Finally, the in situ application and

problems encountered with it are discussed and

solutions and improvement measures for these

problems outlined.

2 BASIC PRINCIPLES

Brine and ice have contrasting electrical properties

in-terms of both charge transport efficiency and

charge transport mechanics. In brine, the differential

movement of the abundant free salt ions constitutes

an electrical current, while conduction in ice is

facilitated by imperfections in the crystalline

lattice.These defects propagate through the structure

by reorientation of molecules and reordering of

bonds, a phenomenon known as protonic

conduction. Pure ice is a poor electrical conductor

because the defect concentration is low, while any

brine included in the ice has a high conductivity.

Electrical methods can be performed on the ice

in-situ and they offer the possibility of automated

sea ice monitoring.The measurement of ice

thickness using coplanar capacitance sensors based

on the different permittivities of sea ice and water.

The basic principle of this apparatus centers on the

capacitance end effects of the capacitance sensor.

(a) (b)

Figure 1: Electric field model of a multi-electrode

capacitance

(a) The basic working principle of the

coplanar capacitance sensor

1-- electric field between the electrode plates .2,4--

exciting electrode plate .3--receiving electrode plates

(b) illustrates the field distribution in the layers

of the underlying medium.

Figure. 1(a) illustrates the basic working

principle of the coplanar capacitance sensor. The

apparatus is composed of exciting and receiving

electrode plates. The plates are isolated by grounded

shield layers. The electric field variation between

the exciting and receiving electrode plates depends

on the ice thickness and so the latter may be

measured indirectly. In 1969, Noltingk first

proposed a high-precision measurement system

based on the end effects of coplanar capacitance. In

addition, he implemented the design structures of

two sensors, namely, a giant coplanar capacitance

sensor and an annular coplanar capacitance sensor.

The two sensors both utilized the capacitance end

effect to measure micro-distances. In 1976,

Noltingk, Nye and Turner presented a mathematical

analysis of the coplanar capacitance sensor for polar

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468

plates that are rectangular in structure. In 1993, Luo

and Chen mathematically analyzed the annular

coplanar capacitance sensor and established the

corresponding mathematical model. In more recent

years, coplanar capacitance sensors have been

widely used for material thickness measurement（

J.Graham,2000 ） moisture or humidity

measurement, etc. Sundara-Rajan et al. used

coplanar capacitance to determine the moisture

content in paper. A. S. Zyuzin et al. adopted

coplanar capacitance to detect the moisture content

in food, such as biscuits, etc. TianMing Chen

employed coplanar capacitance to perform

nondestructive inspection of multi-layer structures.

Nassr also used coplanar capacitance to inspect the

moisture content of a medium with complex

structure.

Figure. 1(b) shows the electric field distribution

produced in the media layers beneath the sensor.

Since the electric field strength decays exponentially

with the thickness of the measured medium, the

permittivity of the medium closer to the fixed

electrode surfaces has a larger impact on the

capacitance between the coplanar electrodes. In the

cross-section shown in Fig. 1(b), a coplanar sensor

is created by two electrodes of width s spaced 2g

apart on two substrate layers of heights h1 and h2

(from the upper surface) and dielectric permittivities

, respectively. In the analysis, the electrode strips

are assumed to have zero thickness and infinite

conductivity. Also, the strip length l is larger than

the width (l > s) to avoid end effects. The

capacitance between the two electrodes due to the

substrate layers is given in closed form as

()

εε

, (1)

where K(k) is the complete integral function, ε0

is the vacuum permittivity (F m–1), and

and

are functions of s and g. They are given by

, and

1kk=−

It can be seen from Eq. (1) that the variation in

the capacitance of the coplanar electrodes shows a

certain functional relationship with the permittivity

of the medium close to the electrode. Since water,

ice, and air present different permittivities at a

certain environmental temperature, a plurality of

electrodes can be installed in parallel in the same

plane to constitute a coplanar multi-electrode

capacitance sensor. Such a sensor can then be

installed vertically in the ice and the water under the

ice. Since the media contacting the electrodes are

ice, water, or air, the capacitances between each

electrode and adjacent electrodes are different. Thus

the vertical measurement of ice thickness can be

realized.

The coplanar multi-electrode capacitance ice

thickness measurement is based on the model in

Figure1. Through the contact made with different

media (such as ice and water) the exciting metal

electrode is affected and the electric field around the

metal electrode is changed. The capacitance of the

metal electrode is thereby altered. It is assumed that

C3 is the capacitance composed by one single

capacitance electrode plate (A in the diagram) and

its adjacent grounding electrode plates. The air’s

permittivity is ε

, ε

is the dielectric coefficient of

the medium, and A is the electrode plate area. When

fluctuates, the capacitances C1, C2, and C3 are

changed. Since the three capacitances are in parallel

in the circuit, the total variation of the capacitance

Cx can be found from Cx = C1 + C2 + C3. In the

equivalent circuit shown in Figure 2, the voltage at

point A is proportional to 1/Cx. The voltage detected

at point B is first transformed into a direct current

(DC) through the internal detector and low-pass

filter of the device. Then the DC signal is processed

by the external microcontroller bearing an analog to

digital (A/D) converter. For example, a single chip

microcomputer (SCM) can be used. The

microcontroller is capable of treating multiple

signals and can thus achieve the goal of the

measurement.

Figure 2: The equivalent circuit for medium measurement

using the capacitance of one coplanar electrode.

The principle underlying ice thickness

measurement using a coplanar multi-electrode

capacitance sensor and corresponding system is

shown in Figure 3. Considering the requirements for

the actual measurement of sea ice, the ice thickness

sensor is designed to be a plurality of electrodes.

More than 100 electrodes are used, which are

uniformly arranged in the same plane (each

electrode measures 1 cm). The detection principle is

An Apparatus for Monitoring Sea Ice Thickness Based on Coplanar Multi-Electrode Capacitance Sensor

469

as follows. The control instrument of the SCM sends

control signals to the sensor to open its multi-switch.

Thus, the sinusoidal signal of first measurement

circuit unit is connected with the first electrode at

the top of the sensor, while the other electrodes are

connected to earth. Then , the sinusoidal signal

flows back to sine power supply to generate a

ground electrode signal by the divider resistance, the

capacitance formed by the metal electrode and the

rest of the electrodes around, and the capacitance

formed by the electrode and the medium.

Figure 3: A schematic diagram illustrating the principle of

the measurement system

Afterwards, the ground electrode signal sends

voltage on the electrode to the A/D input port of the

SCM after transferring the voltage into a DC signal

by rectification, and filtering circuit in sequence.

The SCM collects and saves these voltage signals.

Then the SCM releases a control signal to get

connected with the second electrode from the top.

The voltage on the second electrode is measured,

and so on. Since the permittivities of air, water, and

ice are different at particular environmental

temperatures, the capacitances between each

electrode and its adjacent electrodes are different.

The difference in capacitance is expressed as a

variation in the voltage. Therefore, a set of voltage

data is obtained by measuring, in order, the voltages

on each of the electrodes using the SCM. According

to the voltage jumps on the electrodes, it can be

judged which electrode is surrounded by ice, which

is surrounded by water, and which is surrounded by

air. In this way, the ice thickness can be determined.

The SCM collects data at fixed times separated by a

certain time interval. Finally, it periodically sends

the data acquired to a computer terminal by wireless

transmission.

The coplanar multi-electrode device and its

system consist of two parts, namely, the sensor itself

and its accompanying measuring instrument. The

sensor mainly consists of the metal electrode

sensors, multi-switches, sine signal generators, a

rectifier, and a filter. Part of the circuit board of the

sensor is sealed by encasing it together with the

metal capacitance electrodes. The measuring

instrument is composed of the SCM, the A/D

conversion circuit, the data storage circuit, the GSM

modem, etc. In the circuit design, the circuits

generated by each sine wave generator are combined

with a rectification circuit to form a circuit module.

Each module contains 7 electrodes at most to avoid

parasitic capacitance on the electrodes caused by

wires on the circuit board that are too long. The

SCM control circuit mainly controls the sensor

circuits and thereby detects the ice thickness. The

circuit board of the measuring instrument containing

the SCM is placed on one end of the sensor. It is

insulated from the electrodes by hard plastic sheets.

The surface of the coplanar multi-electrode sensor is

sealed using insulating materials to prevent direct

contact of the capacitance electrodes with the ice

and water. Using the SCM control circuit and

wireless transmission module on the sensor,

automatic unattended remote monitoring of the ice

thickness can be achieved.

Considering that the ice thickness measurement

depends mainly on the measurement and judgment

of the positions of the interfaces between air and ice,

and ice and water, the whole apparatus is generally

chosen to be a long rod shape. A large number of

experiments and comprehensive data results show

that the sensing effect is optimum using 0.3 mm

thick copper foil for the electrode material.

Electrodes are placed every 1 cm, so that the

measuring precision of the sensor is kept to the

centimeter level. In the experiment reported here,

copper foils measuring 6 mm and 4 mm in width

and 15 cm in length are used for the metal electrodes

(the thickness is 0.3 mm, as already said).

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470

Figure 4: Installation diagram of the sensor in

the ice.

Experimental results also suggest that the wider

the copper foil strip is, the lower the voltage on the

electrode, and the larger the capacitance of the

copper strip is. With increasing space between metal

electrodes, the voltage on the metal electrode

gradually grows until it reaches a certain value. This

phenomenon indicates that an increase in the space

between electrodes can reduce the capacitance of

electrodes, however, this reduction will not continue

when a certain value is reached. To better seal the

electrodes, we molded a thin layer of insulating

epoxy resin material on the bottom of grinding

apparatus of PVC material in a selected shape and

volume before laying out the electrodes. Generally,

the epoxy resin layer is around 2 mm thick. When

the epoxy resin had completely solidified, copper

foil electrodes were laid on the surface of the thin

epoxy resin layer at an interval of 4 mm and 1 cm

for one electrode. The installation diagram of the

sensor and the corresponding measuring system for

measuring ice thickness is shown in Figure 4.

3 IN SITU EXPERIMENTS

3.1 In Situ Environment

In March 15, 2016, researchers installed the two sets

of apparatus into the sea ice near Zhongshan station

(specific location 69°22′05.1″ S, 76°21′51.3″ E). The

photograph on the left in Figure 5 shows the in situ

installation of the two sets of measuring devices.

Points A and C are the sites where the measurement

devices are installed. The horizontal distance

between the two sites is 20 m. The right-hand

photograph in Figure 5 presents the in situ

installation of the sensor at point A. At installation,

the in situ snow depth was only 1 cm thick. The

installation steps are indicated below.

Figure 5: In situ installation pictures.

A wooden strip fixed 8 cm below the top of the

sensor was used as a float. A hole was drilled in the

ice’s surface using a hand-cranking ice driller. Then,

the ice thickness around the ice hole was manually

measured using a tape measure and the ice

suspension height was determined using a ruler. The

rod-shaped sensor was vertically inserted into this

ice hole until the float was stuck on the ice surface.

Then the ice hole was filled using ice flakes or snow

to keep the apparatus vertical. After the power

supply was switched on, the apparatus started to

work. Finally, a few holes were drilled in the ice

surface. The storage battery sealed using insulating

material was fixed using wooden rods and ropes to

prevent the wind blowing it away. The initial

number of electrodes of the measurement sensor

exposed to the air at site A was 8, that is, the top

sensor is 8 cm from the ice surface in site A. The top

sensor at site C was 10 cm from the ice surface

initially.

Table 1: The in situ conditions of the measurement

device.

Ite

Site A Site C

Initial snow

thickness (cm)

0.2 0.2

Initial ice

thickness (cm)

26 27

Initial ice

suspension (cm)

4 5

Lowest

temperature (°C)

–33.8

Highest 0.1

An Apparatus for Monitoring Sea Ice Thickness Based on Coplanar Multi-Electrode Capacitance Sensor

471

temperature (°C)

Maximum

snowfall

(

)

Maximum wind

eed

(

m/s

)

40.7

From March 16, 2016 to August 31, 2016, the

lowest and highest temperatures of the sea area at

the two devices were –33.8°C and 0.1°C,

respectively, according to in situ detection. During

the monitoring period, the monitored sea area

experienced many periods of snowfall, and the

highest snow thickness was 31 cm. The sensor

became completely covered by snow, but in a short

period of time most of the snow was blown away by

wind. The maximum wind speed in the detection

area was 40.7 m/s during this period. Table 1

describes the field environment of the detected sea

area during the monitoring period.

3.2 Experimental Results

From March 16 to August 31 in 2016, the southern

region of Australia was in autumn and winter and

Antarctica was in winter. Throughout this time

period, the two measurement devices worked

normally on the sea ice near Zhongshan Station for a

total of 168 days. Measurement was conducted 3

times a day. Thus, 504 groups of data were obtained

from each measurement device. In the experiment,

the Iridium Satellite system’s remote data delivering

service was employed for a week of the experiment.

The rest of the data was collected directly by field

researchers who read the SD memory cards in the

apparatuses at fixed time points.

By preliminarily analyzing the data acquired, it

was found that the maximum daily growth in ice

thickness was 3 cm. We employed the data collected

at 0:00 every day and obtained 168 sets of data. The

ice thickness and daily temperature variation curves

in the detected sea area acquired by the two

measurement devices over the 168 days are shown

in Figure 6. In this figure, the ice thickness variation

at sites A and C are basically consistent. The ice

thickness data detected at the two sites from June to

July are very close. In the two periods with rapid

growth (April 20–May 15 and in August), the ice

thicknesses show larger differences. From March 16

(when the two sets of measurement devices were

installed) to March 28, ice thickness grew from 0 cm

to around 30 cm. (Since the sensors were initially

installed in ice holes with diameters of 10 cm drilled

by the ice driller, the ice thickness grew from 0 cm.

To March 28, the ice thickness in the hole that the

measurement devices were installed in had been

consistent with the surrounding ice thickness.

Figure 6: The ice thickness variation at sites A and C

and the daily mean temperature curve.

In this experiment, the data collected after March

28 is used in the calculation of sea ice growth rate.

That is to say, the sea ice thickness measured by the

two sets of devices from March 16 to March 28

cannot reflect the natural growth condition of sea ice

at the detection sites. Thus, the natural growth rate

of the sea ice is calculated when the sea ice

thickness at the detection sites agreed with that due

to natural growth on March 28. The calculation

formula for the sea ice growth rate is where H

is the

ice thickness, ti is the measurement time, and ti+1 is

the next measurement time .

(a) (b)

Figure 7: Graphs showing the variation in sea ice

thickness and ice growth rate.

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According to this formula, the daily mean

growth rates of the sea ice at sites A and C of the

detection area are 0.618 cm day–1 and 0.498 cm

day–1, respectively. The maximum sea ice thickness

growth rate at site A is observed on April to May 13,

with a value of 0.83 cm day–1, as shown in

Figure 7(a) and 7(b). The minimum sea ice thickness

growth rate at site A is found on June 25 to July 25,

with a value of 0.54cm day–1, as shown in

Figure 7(c) and 7(d).

3.3 Precision Analysis

While monitoring the sea ice, the sea ice thicknesses

at sites A and C were also measured manually using

the hole-drilling method. Providing the weather

permitted, these measurements were carried out

once a day. Figure 8(a) and 8(b) show the sea ice

thickness variation at sites A and C, respectively, as

detected by the measurement device and manually.

It can be seen from Fig. 9 that the device

measurement results are all smaller than those

obtained by manual hole-drilling at both sites A and

C. That is, there is a certain difference between the

sea ice thickness results as measured by the two

measuring devices and by the manual hole-drilling

method. This is attributed to the fact that the

skeleton ice (flocculent ice) on the contacting part

of the sea ice and sea water has a certain thickness.

In a manual hole-drilling measurement, the sea ice

thickness is measured using a tape. Thus, the

thickness of the skeleton ice is included in it.

However, with the device measurements, skeleton

ice is recognized as sea water by the capacitance

sensing electrodes due to its larger water content.

Therefore, the sea ice thickness measured by the

device is smaller than that obtained by the manual

hole-drilling method. The difference is relatively

large during March 28 to April 20. The maximum

value of the difference at site A reaches 9 cm. By in

situ inspection, we conclude that this was because

the ice in the ice hole in which the device was

installed in did not become frozen to the same

thickness as the surrounding ice. The minimum

difference value is 1 cm. The maximum and

minimum difference values at site C are 5 cm and 1

cm, respectively. The difference tends to be a stable

1–2 cm after April 20. Therefore, the device

measurement data and manual hole-drilling

measurement data from April 20 to April 30 are

used for analysis. The deviation D in the device

measurement can be calculated according to the

following formula

%100

d-e

zmzm

×=D (2)

where, e

is the mean ice thickness measured by

the device in the ten days, and d

is the mean sea

ice thickness obtained by the manual hole-drilling

measurement. By calculation, it is found that this

formula is consistent with the work of Kovacs et al.

in 1996 and Haas et al. in 1997.The relative

deviation of apparatus is thus –3.5%.

（a）

（b）

Figure 8: Comparison of the data obtained using the

measurement device and by manual hole-drilling at (a)

site A, and (b) site C.

4 PROBLEMS AND DISCUSSION

The sensor proposed in this study was applied to

detect the sea ice thickness near Zhongshan Station.

However, the sensor is only 1.4 m long, while the

sea ice thickness in the detection area can reach up

to 1.5 m (maximum depth). Moreover, the two

sensors were exposed above the sea surface by 8 and

10 cm. This means that their under-ice measurement

An Apparatus for Monitoring Sea Ice Thickness Based on Coplanar Multi-Electrode Capacitance Sensor

473

lengths were 1.32 m and 1.30 m, respectively.

Therefore, when the sea ice thickness exceeds 1.30

m, the two sensors cannot be used to accurately

measure the sea ice thickness. Thus, the experiment

was terminated when the sea ice thickness exceeded

1.25 m (at the end of August). In addition, during the

6 months of the application, the snowfall thickness

on the sea ice surface was more than 10 cm on May

27 and July 3. Thus the data between the air and ice

snow surface, and snow surface and ice surface

cannot be correctly judged by the sensors.

This study proposes a new apparatus for

measuring ice thickness that uses capacitance.

According to the different dielectric properties of

air, ice, and water, this apparatus determines the air

layer, ice layer, and under-ice water layer

thicknesses using a layered measurement method

and coplanar multi-electrode capacitance sensor.

Moreover, it can also be applied to automatic

real-time monitoring of sea ice thickness in polar

regions and, by extension, to automatic monitoring

of river ice thickness in rivers (or reservoirs) in

winter.

Several problems arise in the application of the

coplanar multi-electrode capacitance ice thickness

sensor:1) Since electrodes are installed in different

positions in the sensor, the influence of the adjacent

electrodes on an electrode is different. This

phenomenon results in different voltages being

detected by two electrodes although the surrounding

medium is the same. This is an inherent problem

arising from the nature of the sensor. The mutual

interference between electrodes can be reduced by

shielding measures, etc., but cannot be completely

eliminated.2) Environmental temperature has a

certain influence on the capacitance presented by the

coplanar electrodes. For electrodes of the same size,

the lower the temperature is, the smaller is the

capacitance formed by one electrode with an

adjacent electrode. As the temperature in the ice

layer varies from top to bottom, the capacitances of

the metal electrodes at the same site are different for

different parts of the ice layer. In this way, the

medium around the electrode may be easily

misjudged. This problem can be solved using

temperature compensation, that is, the

environmental temperature around the electrode is

detected by setting a certain number of temperature

sensors. When the temperature changes, the

electrode capacitance can then be compensated

using a hardware circuit.3) Power supply problems.

Since the ice thickness measurement system is

operated in a low temperature environment, the

power consumption of the electronic components is

increased. Thus, it is a requirement that the whole

system must be provided with a reliable power

supply. In this study, a storage battery with a

relatively large capacity is employed. Moreover, it is

sealed by encasing and placed in the lower part of

the sensor. In this way, the storage battery can be

constantly immersed in river or sea water. As river

water has a temperature around 0°C and sea water

temperature is around –3°C, battery power loss will

not be induced by an overly-low temperature.

5 CONCLUSIONS

The coplanar multi-electrode capacitance ice

thickness detecting sensor and its system is still

currently in a laboratory research and field trial

stage. To realize fixed-site automatic monitoring of

ice thickness, the following problems need to be

further studied and addressed.

First, The dielectric properties of sea ice. Sea ice

has complex structural forms, e.g. pure ice form,

ice-brine form, etc . Therefore, it exhibits different

dielectric properties at the same temperature. This

situation can induce misjudgment of the ice medium

when using the capacitance electrode. Thus, a large

amount of laboratory experiments are needed to

measure the dielectric property of sea ice in its

different forms and to establish a dielectric database

of the ice’s properties as a function of temperature

and form. The results obtained can provide a

database for accurate measurements with the

capacitance electrode.

Second,The structure of the sensor. This problem

is mainly concerned with the size of the coplanar

electrode and the space between electrodes. It

directly affects the measurement precision of the

sensor. Thus, if measurement precision is required to

be improved to ±3 mm, the width of the sensor’s

electrodes can only be 2 mm at most, and the space

width can be at most 1 mm. Moreover, whether the

setting is the optimal plan or not needs to be verified

via simulation. That is, the optimization of the

sensor structure needs to be realized by software

simulation.

In conclusion, an ice thickness sensor based on

coplanar multi-electrode capacitance has achieved

preliminary success in a laboratory study and field

experiment. After the problems above are solved,

the system will be considerably improved. Using the

system, it is feasible to measure the thickness of

river and sea ice at fixed sites. The ice thickness data

thus obtained can subsequently provide reliable data

for research on the thermodynamics of the ice.

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474

ACKNOWLEDGMENTS

We are grateful to the Chinese Arctic and Antarctic

Administration for its logistic support during our

experiment; to Mr. Zhao jiecheng and Mr. Han

desheng,for their field-work support; to the

Meteorological Office of Zhongshan Station for

providing meteorological data. Three anonymous

reviewers are thanked for their comments, which

considerably improved this work.

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