CEN/TS 15518-4:2023

SLOVENSKI STANDARD
01-januar-2024
Oprema za zimska vzdrževalna dela - Cestni vremensko-informacijski sistemi - 4.
del: Preskusne metode za stacionarno opremo
Winter maintenance equipment - Road weather information systems - Part 4: Test
methods for stationary equipment
Winterdienstausrüstung - Straßenzustands- und Wetterinformationssysteme - Teil 4:
Prüfverfahren bei stationären Einrichtungen
Matériel de viabilité hivernale - Systèmes d'information météorologique routière - Partie 4
: Méthodes d'essai pour les matériels fixes
Ta slovenski standard je istoveten z: CEN/TS 15518-4:2023
ICS:
07.060 Geologija. Meteorologija. Geology. Meteorology.
Hidrologija Hydrology
13.030.40 Naprave in oprema za Installations and equipment
odstranjevanje in obdelavo for waste disposal and
odpadkov treatment
35.240.99 Uporabniške rešitve IT na IT applications in other fields
drugih področjih
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

CEN/TS 15518-4
TECHNICAL SPECIFICATION
SPÉCIFICATION TECHNIQUE
November 2023
TECHNISCHE SPEZIFIKATION
ICS 07.060; 13.030.40; 35.240.99 Supersedes CEN/TS 15518-4:2013
English Version
Winter maintenance equipment - Road weather
information systems - Part 4: Test methods for stationary
equipment
Matériel de viabilité hivernale - Systèmes Winterdienstausrüstung - Straßenzustands- und
d'information météorologique routière - Partie 4 : Wetterinformationssysteme - Teil 4: Prüfverfahren bei
Méthodes d'essai pour les matériels fixes stationären Einrichtungen
This Technical Specification (CEN/TS) was approved by CEN on 15 October 2023 for provisional application.

The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to
submit their comments, particularly on the question whether the CEN/TS can be converted into a European Standard.

CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS
available promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in
parallel to the CEN/TS) until the final decision about the possible conversion of the CEN/TS into an EN is reached.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2023 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TS 15518-4:2023 E
worldwide for CEN national Members.

Contents Page
European foreword . 5
Introduction . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 8
4 System and test setup definition . 8
4.1 Introduction . 8
4.1.1 General. 8
4.1.2 General rules for issue of certifications according to this standard . 9
4.1.3 General requirements for estimation of uncertainties of test procedures and tolerances . 9
4.2 Pavement surface temperature test for embedded sensors . 10
4.2.1 General. 10
4.2.2 Stabilized temperature test . 10
4.2.3 Transient temperature test . 11
4.3 Temperature test for embedded sensors for the road body temperature . 13
4.4 Water film thickness test for embedded sensors . 13
4.4.1 General. 13
4.4.2 Test method overview . 13
4.4.3 Test equipment . 14
4.4.4 Test procedure . 14
4.4.5 Result analysis . 15
4.5 Road surface condition for embedded sensors . 16
4.5.1 General. 16
4.5.2 Test method . 16
4.5.3 Test equipment . 17
4.5.4 Test procedure . 17
4.5.5 Result analysis . 17
4.6 Freezing temperature for embedded sensors . 17
4.6.1 General. 17
4.6.2 Test method . 18
4.6.3 Test equipment . 18
4.6.4 Test procedure . 20
4.6.5 Result analysis . 21
4.7 Amount of de-icing agent (g/m ) for embedded sensors . 21
4.7.1 General. 21
4.7.2 Test method . 21
4.7.3 Test equipment . 21
4.7.4 Test procedure . 22
4.7.5 Result analysis . 23
4.8 Surface Temperature test for remote sensors . 23
4.8.1 General. 23
4.8.2 Test method . 23
4.8.3 Test equipment . 23
4.8.4 Test procedure . 23
4.8.5 Result analysis . 23
4.9 Water film thickness and surface condition test for remote sensors . 24
4.9.1 General information . 24
4.9.2 Test method overview . 24
4.9.3 Test equipment. 24
4.9.4 Test procedure . 25
4.9.5 Result analysis . 26
4.10 Frost detection test for remote sensors . 27
4.10.1 Test method overview . 27
4.10.2 Test equipment. 27
4.10.3 Test procedure . 28
4.10.4 Result analysis . 28
4.11 Ice film thickness and road condition test for remote sensors . 28
4.11.1 Test method overview . 28
4.11.2 Test equipment. 28
4.11.3 Test procedure . 29
4.11.4 Result analysis . 30
4.12 Air temperature test for atmospheric sensors . 31
4.12.1 Method . 31
4.12.2 Assessment criteria . 31
4.13 Relative humidity test for atmospheric sensors . 31
4.13.1 Method . 31
4.13.2 Assessment criteria . 32
4.14 Dew point temperature test for atmospheric sensors . 32
4.15 Precipitation detection time test for atmospheric sensors . 32
4.15.1 General . 32
4.15.2 Test method . 32
4.15.3 Result analyses . 32
4.16 Precipitation type test for atmospheric sensors . 32
4.16.1 General . 32
4.16.2 Test equipment. 32
4.16.3 Measuring arrangement. 33
4.16.4 Measurement value acquisition . 33
4.16.5 Assessment procedure. 33
4.16.6 Result analysis . 33
4.17 Precipitation intensity test for atmospheric sensors . 34
4.17.1 General . 34
4.17.2 Test method . 34
4.17.3 Result analysis . 38
4.18 Amount of precipitation test for atmospheric sensors . 38
4.18.1 General information . 38
4.18.2 Test method . 38
4.19 Wind speed test for atmospheric sensors . 40
4.19.1 Method . 40
4.19.2 Assessment criteria . 40
4.20 Gust of wind test for atmospheric sensors . 40
4.21 Wind direction test for atmospheric sensors . 40
4.21.1 Method . 40
4.21.2 Assessment criteria . 40
4.22 Visibility test for atmospheric sensors . 40
4.22.1 Test method . 40
4.22.2 Test equipment. 40
4.22.3 Test procedure . 41
4.22.4 Result analysis . 41
Bibliography . 42

European foreword
This document (CEN/TS 15518-4:2023) has been prepared by Technical Committee CEN/TC 337 “Road
operation equipment and products”, the secretariat of which is held by AFNOR.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes CEN/TS 15518-4:2013.
CEN/TS 15518-4:2013:
— revised general specifications;
— revised or added test specifications for embedded sensors:
— pavement temperature;
— road body temperature;
— road surface condition;
— water film thickness;
— freezing temperature;
— amount of de-icing agent;
— added test specifications for remote sensors:
— surface temperature;
— water film thickness and surface condition;
— frost detection;
— ice film thickness and road condition;
— revised test specifications for atmospheric sensors:
— air temperature;
— relative humidity;
— dew point temperature;
— wind speed;
— wind direction;
— precipitation intensity;
— visibility;
— deleted test specifications for atmospheric sensors:
— snow depth.
EN 15518, Winter maintenance equipment — Road weather information systems, is currently composed
of the following parts:
— Part 1: Global definitions and components;
— Part 2: Road weather — Recommended observation and forecast;
— Part 3: Requirements on measured values of stationary equipment;
— Part 4 (CEN/TS): Test methods for stationary equipment.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
According to the CEN/CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to announce this Technical Specification: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Introduction
Road Weather Information Systems (RWIS) are complex structures used for road maintenance decision
support, which feature as a rule the following components: meteorological sensors and instruments,
transmission technology, computer systems for processing, representation and storing of information,
road weather forecasts, alarms, in relation to traffic control and traffic information systems and more.
This European specification lays down the test procedures to verify the requirements on stationary
equipment specified in EN 15518-3.
The aim is to allow for objective and reproducible measurement analysis and evaluation.

1 Scope
This document specifies the test methods, the experimental set-up and result analysis for the laboratory
qualification of stationary equipment within a RWIS.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
EN 15518-3, Winter maintenance equipment — Road weather information systems — Part 3: Requirements
on measured values of stationary equipment
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 15518-3 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at https://www.electropedia.org/
4 System and test setup definition
4.1 Introduction
4.1.1 General
The tests described hereafter apply to either a complete system (which can influence the measured value)
consisting of sensor, processing electronics and associated terminal program software necessary to
acquire, display and store the measurements in a digital form, or some specific parts of the whole system
when the inputs can be simulated, as specified by the manufacturer. Figure 1 below is an illustration of
the possible functional components of a system.
The manufacturer shall specify and supervise the material set-up for the test set-up.
The manufacturer shall not change the test set-up during the tests. The data shall be readable during the
whole test. The whole tests shall stop in case the manufacturer changes the test set-up.
If a single sensor provides measurements subject to more than one test procedure, it shall always be
tested against all these procedures within the same test campaign and by the same laboratory. This is
also valid for tests after technical changes to a sensor.
Figure 1 — Possible functional components of a system
Test protocols shall state the version and type of hardware, firmware and software components as well
as the material set-up during the test.
In case of major technical changes to one or other of these components which affect the requirements of
EN 15518-3, the manufacturer shall seek new certification. In case of minor changes not affecting the
requirements of EN 15518-3, the manufacturer shall indicate the changes and, upon request, provide the
demonstration that the changes did not affect in an adverse way the system which was originally tested
and that the new system still meets the standard.
Generally, in case a sensor was tested as a single device and meets the requirements of this document,
and its nominal output can be simulated, the RWIS manufacturer shall be allowed to only demonstrate
that the measuring chain cannot influence the raw signal in a manner to exceed the allowed tolerance.
Therefore, this document applies to three possible configurations:
— sensor as single device;
— electronics with simulated sensor inputs;
— complete system.
4.1.2 General rules for issue of certifications according to this standard
Test certificates, which confirm, that a product fulfils the requirements of EN 15518-3, can be issued by
every acknowledged laboratory or institution, which is able to fulfil the requirements for performing the
tests. Except otherwise is specified for specific sensors.
4.1.3 General requirements for estimation of uncertainties of test procedures and tolerances
For each test procedure, the testing laboratory shall carry out an assessment of the uncertainties to be
applied, due to the execution of the test procedures and the used test equipment. All inaccuracies shall
be added, which influence the reference value of a test. The uncertainty range resulting from the
reference value to be compared shall be documented and the tolerance range to be applied for the
acceptance of the test result shall be defined and documented before implementation.
EN ISO/IEC 17025 should be considered accordingly.
The tolerance budget for acceptance consists of the accuracy requirement budget (Acc) derived from the
corresponding standard and the total uncertainty (Unc) of the reference and test method of the
laboratory.
2 2
TOL unit =± Acc unit + Unc unit
( ) ( ) ( )
where
Tol is the Tolerance budget in terms of the value unit;
Acc is the Accuracy requirement in terms of the value unit;
Unc is the total uncertainties of the test procedure in terms of value unit.

4.2 Pavement surface temperature test for embedded sensors
4.2.1 General
This test is divided into two parts, a stabilized temperature test in order to prove the ability of the sensor
to provide accurate temperature reports under stabilized conditions and a transient temperature test in
order to prove the ability of the sensor to react appropriately for cooling on the surface e.g. by a clear
night.
The device under test shall be able to provide valid measurement values at least every minute via a digital
communication interface for processing by a computer.
4.2.2 Stabilized temperature test
4.2.2.1 Test method
The sensor is placed into a temperature calibration bath at stabilized temperatures. The temperature
response of the sensor is compared to the temperature response of a reference thermometer.
4.2.2.2 Test equipment
This test requires the following equipment:
— thermal calibration bath;
— reference thermometer with accuracy ±0,1 °C and sampling rate of max. 10 s.
4.2.2.3 Test procedure
Ensure a proper connection of the sensor to be tested and the whole measurement chain. The
measurements of the sensor and the reference thermometer shall be recorded throughout the test.
Set the bath to the given temperature (ensure a uniform temperature of the bath (difference < 1 °C) by
stirring the liquid). The temperature variation of the bath shall not exceed ±0,1 °C throughout the
duration of each test.
Place the sensor into the liquid bath so that it does not touch the bottom or the walls of the container.
The measurement period shall start as soon as calibration bath and DUT has stabilized (for 5 min
within ±0,1 °C):
— the reference thermometer has shown bath temperatures within requirements for 6 min.
The measurement period ends as soon as one of the following conditions is met:
— 5 consecutive samples (or all the samples during 10 min, whichever is longer) of the sensor to be
tested are recorded within the accuracy requirements;
— 15 samples of the sensor to be tested (or 30 min, whichever is longer) have elapsed since the start of
the measurement period.
The test shall be performed at each of the following temperatures (more test points can be added):
— 10 °C;
— 0 °C;
— −15 °C.
4.2.2.4 Result analysis
The test is considered successful if 5 consecutive samples (or all the samples during a period of 10 min,
whichever is longer) are recorded within the accuracy requirements, specified in EN 15518-3 plus the
total uncertainties of the test itself (see also 4.1.3) which is at least additional ±0,1 °C, due to the above-
mentioned bath and reference accuracy.
4.2.3 Transient temperature test
4.2.3.1 Test method
The sensor to be tested is placed on the surface of a sand filling in a box. The sand is soaked with water.
Reference temperature sensors are placed around the sensor, which are also located just equal to the
surface of the sand filling. In order to simulate the down cooling of the surface e.g. by radiation of a clear
cold night, a very cold metal body is placed at a defined distance. The change in temperature at the surface
is continuously recorded by the reference sensors and DUT every 10 s. The trend of the surface
temperature reports of the sensor to be tested and the mean value of the reference sensors are compared.
The sensor to be tested should be able to report the surface temperature change in a certain time after
start of the test within the required temperature accuracy defined in EN 15518-3 and within a tolerance
budget due to the uncertainties of the test procedure and reference sensors.
4.2.3.2 Test equipment
The following equipment is required:
— a container made out of wood or plastic, which have less heat conductivity and is watertight. The
container shall be at least two times larger at each side as the maximum dimensions of the sensor to
be tested and at least 30 cm deep. The container is filled up to 1 cm below the top of the box walls
with sand (grain size ca. 0,1 mm to 0,6 mm). The box with sand should be filled up with water so the
sand is soaked completely with water but the water should not exceed the surface of sand filling;
— a metal body made of aluminium (or similar material with a high heat capacity) with dimensions at
least 20 % larger than the dimensions of the sand box and a thickness of at least 4 cm;
— a freezer, able to freeze down the aforesaid metal body to temperatures down to −25 °C;
— three PT100 layer type resistors as reference sensors with an accuracy of ±0,1 °C, connected to an
electronic measurement system, able to provide the temperature measurement values at least every
10 s via a digital interface;
— a computer (e.g. PC, LabTop) based system which is able to acquire the data of the reference and DUT
sensors at least every 10 s via digital communication interface and archive the data together with a
time stamp;
4.2.3.3 Test procedure
Place the sensor to be tested in the wet sand filling of the box, so that the sensor is completely surrounded
from sand and the surface of the sensor is equal to the surface of the sand filling – as it is the case, when
the sensor is normally installed in a road pavement surface. For an illustration of the setup see
Figure 2.
Place at least three layer type reference sensors into the surface of the sand filling around the sensor to
be tested in a distance not more than 2 cm from the body of the sensor. Reference sensors should be
located approx. 3 mm depth below sand surface.
Place the metal body into a freezer and let the body cool down to ca. −25 °C.
Maintain the ambient humidity and temperature of the test considerable stable (±1 °K) at +15 °C
temperature.
The test can be started, when the mean surface temperature reported by the reference sensor and the
surface temperature reported by the sensor to be tested are quite stable (±0,2 °K) – means no significant
change over a period of 5 min.
If the aforesaid conditions are fulfilled, then take the metal body out of the freezer and put it without
delay over the sand box, so that the metal body covers the top of the sand box in about 1 cm distance to
the surface of the sensor to be tested and the sand filling. The Metal Plate should be isolated to the
environmental air of the laboratory by using Polystyrene (PS) foam or similar. And that the metal plate
sits tightly on the box to prevent the surrounding air from influencing the air gap between the sensor
surface and the metal plate.
Key
1 metal plate
2 DUT (Device under test)
3 reference temperature probe
4 wet sand filling
5 isolation (e.g. Polystyrene (PS) foam)
Figure 2 — Sketch to illustrate the setup of the test (only for demonstration – not true to scale)
Record the surface temperature and timestamp as the starting point of the test.
Let the surface in the sand container cool down and continue the continuous data acquisition until the
minimum of the surface temperature, reported by the reference sensors is reached and no decrease of
the temperature over a period of 10 min can be encountered. If the aforesaid condition is fulfilled, then
the test is finished.
4.2.3.4 Result analysis
Carefully estimate which uncertainties are associated with the reference measurement and the entire test
procedure and document them so that they can later be used as a tolerance budget for the reference value
in the evaluation.
Calculate the mean value of the three reference sensors for every timestamp.
Calculate the 90 % level of surface temperature between the starting temperature and the minimum of
the mean surface temperature from the reference sensors. Determine the time stamp at which the 90 %
level of the reference mean surface temperature was reached. Determine the reported surface
temperature of the sensor to be tested (DUT) at the same time stamp. Find the difference between the
mean surface temperature and the reported surface temperature of the DUT at the timestamp of the
foresaid 90 % level.
The test is fulfilled when:
— the determined difference of the mean reference surface temperature and the reported surface
temperature of the DUT is less or equal to the required accuracy of the DUT at that temperature
under transient conditions - according to EN 15518-3 - plus the tolerance budget given by the
estimated uncertainties of the reference temperature sensors and test procedure itself, which is at
least additional −0,5 and +1,5 °C due to low wet sand correlation against true asphalt or concrete
surface of the road. The lower tolerance budget is an addition of the Lower limit of accuracy
requirement of EN 15518-3 plus −0,5 °C and the upper tolerance budget is an addition of the upper
limit of the accuracy requirement plus +1,5 °C.
4.3 Temperature test for embedded sensors for the road body temperature
Test is completed same way as described in stabilized temperature test.
4.4 Water film thickness test for embedded sensors
4.4.1 General
In order to ensure the test covers the whole required measurement range, with this method water film
thickness can be measured from maximum water film height down to 0,1 mm on embedded sensors,
below 0,1 mm linear approximation to 0 mm is used.
4.4.2 Test method overview
A thick (≥3 mm) water film is applied on the sensor and then allowed to start to evaporate. The
evaporation may be accelerated with a fan. As the water evaporates, the film thickness decreases. The
film thickness is measured periodically with a depth micrometer.
A linear approximation of the evaporation process is computed from the micrometer measurements. If
the measurements do not correspond to a linear evaporation rate, the test needs to be redone, possibly
with a higher degree of environmental control.
The sensor shall report the correct water film thickness in relation to the linear water level
approximation.
4.4.3 Test equipment
This test requires the following equipment:
— a depth micrometer (because, for embedded sensors, weight measurement as reference can be
difficult);
— test body (optional, if leak tight barrier installed directly on sensor);
— separate leak tight barrier, if test body leaking;
— a stable micrometer rack;
— fan (optional).
For illustration, see Figure 3.

Key
1 micrometer
2 test body
3 leak tight barrier
4 stable micrometer rack
Figure 3 — Necessary test equipment (fan not included)
4.4.4 Test procedure
Ensure a proper connection of the sensor to be tested and the whole measurement chain.
If a fan is not used, ignore the rest of fan-related instructions. If using a fan, the fan should be used in the
same way during the whole procedure (in order to ensure a linear evaporation rate).
Measure a dry reference depth level with the micrometer on the sensor surface.
Apply a water film thickness greater than 3 mm over the sensor. The film thickness should remain over
3 mm until the start of micrometer measurements. Start accelerating the evaporation with the fan.
Wait until the sensor water film thickness readings are stable, or for 6 min after sensor reports “Not Dry”
road surface condition, whichever is longer.
Stop the fan temporarily. Measure the water film thickness with the micrometer. Lower the micrometer
tip very carefully and stop as soon as the tip touches the water surface. Micrometer tip should be
sharpened (not flat type). The contact moment should be indicated with a visible surface tension reaction.
Record the reading; the difference between this reading and the dry reference is the thickness of the
water film. Record also timestamp for each measurement.
NOTE Shortly repeated measurements of the same film thickness will likely yield different results, since the
surface tension reaction slightly manipulates the distribution of water on the sensor surface, especially with lower
film thicknesses. Use only the first reading or wait 1 min for the water surface to reset before measuring again.
Restart the fan. The fan’s power, location and direction should remain constant during the test, with the
exception of the measuring.
At regular intervals stop the fan and measure the water film thickness with the micrometer, as described
before. The measurement should take no longer than 1 min.
The exact interval can be decided based on e.g. the length of the measurement cycle, but the interval
should be constant during the test.
Once the water level measured by the micrometer is below or at 0,1 mm, cease measurement by
micrometer. Keep the fan on.
Visually observe the sensor surface. And record the times at which the surface looks moist and completely
dry.
After visual confirmation of dryness, continue measurements for 20 min.
4.4.5 Result analysis
The micrometer measurement can cause erroneous sensor readings during measurement. The affected
samples or measurement cycles may be removed from the data.
Fit a linear approximation of the water level based on the micrometer measurements down 0 mm.
Minimize mean square error of the fit. If the micrometer measurements are not all within ±5 %
or ±0,05 mm (whichever is higher) of the fitted linear approximation, reject and repeat the test
procedure. Don’t include the visual observation of dryness in the fit.
Key
X measurement duration (min)
Y water film thickness (mm)
depth micrometer measurements
linear fit to micrometer measurement points

example sensor readings
Figure 4 — Example plot of evaporation measurement
Figure 4 shows an example of measurement points, linear approximation and sensor samples. The sensor
samples are compared to the linear fit of the micrometer measurements.
The test is successful if the discrepancy between each water film thickness reading and the corresponding
value of the linear thickness approximation is within the tolerance, between the thicknesses of 0,05 mm
and 3,0 mm. The acceptable tolerance is the required accuracy range of the sensor to be tested according
to EN 15518-3 plus the uncertainty of the test itself, which is at least ±5 % or ±0,05 mm (whichever is
higher) due to the approximation (see also 4.1.3).
4.5 Road surface condition for embedded sensors
4.5.1 General
Unless otherwise specified, a valid measurement value shall be delivered by the system at latest 6 min
after the test conditions are met.
4.5.2 Test method
4.5.2.1 General
The test shall take place in a laboratory environment. The sensor shall be installed as described in 4.4.
4.5.2.2 Dry
The output of the sensor to be tested shall be compared with the condition “Dry”.
4.5.2.3 Not Dry
A liquid film thickness corresponding to the requirement “Not Dry” of EN 15518-3 shall be applied and
maintained over the sensor.
The output of the sensor to be tested shall be compared with the condition “Not Dry”.
4.5.3 Test equipment
This test requires the following equipment:
— equipment (accuracy better or equal to ±10 % for a thickness of 0,01 mm) to control and measure
thicknesses of liquid solutions over the sensor (see also 4.4.3);
— reference temperature probe (air and pavement);
— test setup as per 4.4;
4.5.4 Test procedure
The test procedure can be carried out in connection with the water film thickness test, described in 4.4.
4.5.5 Result analysis
4.5.5.1 Dry or Not Dry
The test is successful if both following conditions are met:
— a first “Not Dry” road surface condition has been recorded within 6 min after the start of the test and
will be recorded unchanged as long as condition change to Dry state.
— the “Dry” road surface condition change from Not Dry has been recorded between time (±2 min)
when surface visually looks moist and completely dry (moist surface looks darker than dry surface,
but no visual layer of water detectable).
4.6 Freezing temperature for embedded sensors
4.6.1 General
The test is only applicable for active sensors, not for passive sensors.
The test shall take place in a climatic chamber. The sensor shall be setup as per 4.4 above.
Unless otherwise specified, a valid measurement value shall be delivered by the system at latest 6 min
after the test conditions are met.
NOTE End user or manufacturer can specify other chemicals or combinations thereof.
WARNING — The equilibrium relative humidity for sodium chloride (NaCl) is very high for low
temperature (88 % for −15 °C). This may ind
...