SARAD Smart Radon Sensor User manual
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Manual_Smart-Radon-Sensor_EN_12-03-2020.docx
Table of content
TABLE OF CONTENT ...................................................................................................................... 2
INTRODUCTION............................................................................................................................ 3
THE INSTRUMENT......................................................................................................................... 4
Controls................................................................................................................................................ 4
Power supply ....................................................................................................................................... 6
Main power supply........................................................................................................................... 6
Back-up batteries ............................................................................................................................. 6
Batteries replacement ......................................................................................................................... 8
SELECTION OF THE RIGHT LOCATION FOR EXPOSURE AND INSTALLATION...................................... 9
SELECTION OF THE RIGHT INTEGRATION INTERVAL ....................................................................... 9
MEASUREMENT ......................................................................................................................... 10
LED INDICATORS......................................................................................................................... 11
COMMUNICATION INTERFACES .................................................................................................. 13
RS-485................................................................................................................................................ 13
General........................................................................................................................................... 13
Selection of the transfer protocol, addressing .............................................................................. 13
Implemented functions.................................................................................................................. 14
USB..................................................................................................................................................... 15
ANALOGUE OUTPUT................................................................................................................... 16
4..20mA current loop......................................................................................................................... 16
ALERT SWITCH............................................................................................................................ 17
SUPPLEMENTARY EQUIPMENT ................................................................................................... 18
Pressure sensor.................................................................................................................................. 18
CO2gas sensor ................................................................................................................................... 18
DISPOSAL INSTRUCTIONS ........................................................................................................... 19
TECHNICAL DATA........................................................................................................................ 20
Smart Radon Sensor .......................................................................................................................... 20
Wireless switch .................................................................................................................................. 22
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Introduction
The Smart Radon Sensor is an innovative Radon monitor, designed for integration in building
automatization systems. Thanks to the broad spectrum of interfaces one can integrate the sensor
with relative small effort within an existing infrastructure. The high sensitivity allows for quick and
precise determination of Radon value, so the device is suitable for controlling the ventilation
systems.
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The instrument
Controls
Fig. 1. - Front panel controls
Fig. 2. - Bottom panel controls
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1
RS-485 port „D-“
2
RS-485 port „D+“
3
4..20mA current loop „-“(GND)
4
4..20mA current loop „+“ (Iout)
5
DC external power supply „-“(GND)
6
DC external power supply „+“ (12÷24V)
7
Switch output port 1
8
Switch output port 2
Tab. 1. - Ports definition of terminal block.
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Power supply
Main power supply
The smart Radon Sensor requires an external power supply in range from 12V up to 24V. The
maximal current consumption does not exceed 50mA (including 20mA of current loop’s maximal
signal and active LEDs, but without usage of the CO2 sensor).
The connection ports for a power supply are shown in figure 1 and defined in table 2. Two ports of
the terminal block with the description „DC-„and „DC+“, at the device`s front panel, are ground and
positive potential respectively. It is recommended to use the power supply unit with a galvanic
isolation for supplying the Smart Radon Sensor. The galvanic isolation is of importance in case the
analogue output is utilized AND the 0..20mA inputs of the data log system are referenced to the
ground potential (e.g.: the current signal is transformed into the voltage value through a defined
resist).
Back-up batteries
The device is equipped with an internal backup power supply (UPS) consisting of two LR3 (AAA)
batteries. This feature allows one to continue the measurement seamlessly if main power supply
failure occurs.
Without DC connection the backup will supply the device for approximately two weeks. In such
circumstances the current loop as well as (if present) CO2 sensor will be deactivated, and the LEDs
functionality will be reduced. If the cell voltage drops below 1,0V, then the current measurement will
be interrupted and the instrument enters the standby mode. Once the main powers supply recovers
or new batteries are placed, the stored measurement data will be accessible immediately.
The instrument accepts alkaline as well as NiCd or NiMH batteries. Attention! Do not use lithium-ion
batteries because their cell voltage is 3V or 3,6V. For maximum operational period we recommend
the usage of alkaline batteries which are optimized for low loads.
It is also recommended to insert the batteries prior to mounting the device and connecting the
terminal block. The placement of the batteries is described more in detail in the next chapter.
Important: The real time clock of the instrument must be set by software after inserting the
batteries. The rechargeable batteries cannot be charged once placed in the instrument. For
stationary operation alkaline batteries are recommended. In contrary to rechargeable batteries, the
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alkaline batteries do not suffer from excessive self-discharge process and therefore are able to keep
their initial electrical capacity for over 10 years.
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Batteries replacement
For battery replacement, the rear cover has to be removed. To do that, both screws (A in fig. 3) at
the backside must be unscrewed at first. After that, the cover can be detached by tilting as shown in
picture 4. Please, pay special attention to the correct polarity of the batteries when inserting them
(fig. 5). Change both batteries at the same time because differing charging levels may lead to failures.
Use always batteries of the same type.
Fig. 3. - Remove both screws (A) at the rear
panel.
Fig. 4. - Remove the rear cover. Tilt it at the
round edge as shown.
Fig. 5. - Insert batteries (AAA/LR3) left and right
(take care for right polarity!).
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Selection of the right location for exposure and installation
The instrument should be placed at a location which is representative for the indoor air quality of a
room. The incidence of direct light and exposure to strong heat sources should be avoided. For
permanent installation, the Smart Radon Sensor can be mounted on a wall using a wall mounting clip
(accessory). Attention has to be paid because the wall itself could be the origin of the Radon inside a
room. This would result in an increased concentration in the surrounding of the surface. Some
comparison measurements at the preferred mounting position and in the middle of the room (each
at least a few days under similar weather conditions) will show if this is the case or not.
When the mounting of the device is accomplished the terminal block can be wired. If the batteries
were replaced before the installation had taken place, the internal clock has to be set with Radon
Vision software over USB connection.
Fig. 6. –The wall mounting clip.
Fig. 7. - Smart Radon Sensor with the mounting
clip.
Selection of the right integration interval
It is possible to adjust the sampling interval of the Smart Radon Sensor between 1 and 255 minutes.
From the physical point of view it makes no sense to choose intervals shorter than 30 minutes
because the response time of the instrument is in that order. If the expected Radon concentrations
are in the range or less than the statutory reference level of 300Bq/m³, an interval of 60 minutes
(default setting) should be used. Frequent zero readings for individual sampling intervals indicate
that the chosen interval is too short.
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Measurement
The measurement starts autonomously after replacing the batteries or connecting the main power
supply. The first measurement result will be available as soon as the first sampling interval is
accomplished. Newly acquired values will be appended periodically to the previously stored results.
The measurement cannot be stopped by the user.
Each year the voltage of the batteries should be checked. This can be done e.g.: by using Radon
Vision software and USB connection. Older data in the memory, which are no more needed, can also
be deleted by means of the software.
Radon activity above alarm threshold value (which is settable) will be indicated by LEDs at the front
panel (fig. 1.). Simultaneously the alert switch will be activated. Please refer to the chapters: „LED
indicators” and „Alert Switch”.
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LED indicators
The Smart Radon Sensor has three color LEDs at the front panel. Their purpose is to indicate the state
of the instrument. The table below (tab. 2.) sums up all possible LED signals.
Permanent ON
RADON < 50% • AlarmTH(*)
Permanent ON
50% • AlarmTH =< RADON <
100% • AlarmTH
Permanent ON
RADON >= 100% • AlarmTH
Blinks
USB connection present
Blinks
Internal sensor clock not set
Blinks short
Main power supply failure(**)
Tab. 2. - LEDs signals.
(*)AlarmTH –Alarm threshold for Radon.
(**)The green and the yellow LED switched OFF, the analogue output deactivated.
Example: AlarmTH = 300Bq/m³.
The green LED will be active at Radon concentration below 150Bq/m3.
The yellow LED will be active at Radon concentration between 150Bq/m3and 300Bq/m3.
The red LED will be active at Radon concentration above 300Bq/m³.
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In case the instrument additionally encloses CO2 sensor the meaning of the LEDs signals changes as
stated below, in the table 3.
Permanent ON
RADON < 100% • AlarmTH
CO2 < 1000ppm
Permanent ON
CO2 >= 1000ppm
Tab. 3. - LEDs signals for Smart Radon Sensor with CO2 Sensor.
The meaning of all other signals stays unchanged.
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Communication interfaces
For a communication between the Smart Radon Sensor and the data acquisition system two digital
interferences are provided. The RS-485 standard serial interference allows user to integrate the
instrument within corresponding network. The USB interface provides a quick way for sensors
configuration and maintenance. Once the USB cable is attached to the device, the RS-485 interface
will be automatically disabled. In such a situation only USB communication is possible. After
removing the USB cable the RS-485 interface will be reactivated.
RS-485
General
The communication over RS-485 interface can be realized with usage of two protocols: proprietary
SARAD protocol or industrial standard MODBUS RTU. The MODBUS protocol supports only the
transmission of the recent readings. For all other functions the SARAD standard protocol has to be
used. The protocol frames are explained in detail by the document “SARAD_MODBUS_Protocol”. The
complete MODBUS Documentation can be found in the internet under “modbus.org”.
Selection of the transfer protocol, addressing
To identify an instrument within a network, a unique address in the range of 1…250 must be
assigned. This address and the bus speed for MODBUS protocol can be programmed into the
instrument using the initialization software „Init_RadonScout”.
Important: The edit field „Address” contains, after loading the configuration parameters with „GET”
button, the current instrument address. Now, the desired address can be entered and transferred to
the instrument with „SET” button. The drop-down list labeled „Baudrate[bps]” contains two entries:
„9600” and „19200”. Those are used to select MODBUS protocol speed.
Please note that the parameters have to be read at first before uploading a new setting. Otherwise
the existing parameters will be permanently overwritten.
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Fig. 8. - Program window of the „Init_RadonScout”.
Selection of the desired operation protocol for RS-485 interface is performed with a „protocol
switch“ placed at the bottom side of the instrument (fig. 2.). This slide switch in the „M“ position
corresponds to the MODBUS protocol. The „S“ position of the slide switch activates the SARAD
protocol.
Implemented functions
Function code 0x03 (read holding register)
Valid register addresses are:
Register
address
Register content
Number of registers
Format
0x0000
Radon concentration [Bq/m3]
2
Float
0x0002
Statistical error of Radon concentration [%]
2
Float
0x0004
Average Radon concentration since last start [Bq/m3]
2
Float
0x0006
Battery voltage [V]
2
Float
0x0008
Temperature [°C]
2
Float
0x000A
Relative humidity [%]
2
Float
0x000C
Barometric pressure [mbar] / CO2 concentration [ppm]
2
Float
Tab. 4. - MODBUS RTU register addresses.
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IEEE 745 float values (4 Byte) are transmitted as two sequential 16 bit registers. The number of
registers to be read must be two. That means, only one value can be transmitted per frame. Other
values and not stated register addresses will cause an exception response.
USB
The additional communication interface, conform to USB standard, allows user to read out the
measurement data and to adjust the operating parameters of the Smart Radon Sensor. The interface
requires a software driver which can be downloaded from the SARAD company website. Within the
Radon Vision software the USB communication path appears as a new COM port. During USB
communication with the instrument the RS-485 terminal of the device is disabled. On the other hand
the analogue output (current loop) and the alert switch are still available and active.
Warning: In case of the USB transmission only SARAD protocol will be supported independent from
„protocol switch”. After detaching the USB cable from the instrument the RS-485 interface will be
reactivated with protocol selection according to the position of the slide switch.
The device cannot be powered via the USB port.
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Analogue output
4..20mA current loop
The Smart Radon Sensor provides an analogue output with current signal from 4 up to 20mA
(so called „current loop”). This feature offers a reliable way for transmitting the measurement signal
over long distances. The terminal ports for the current loop are designated in figure 2 and table 1.
At the end of each integration interval, current value will be calculated according to the Radon
activity and the chosen measurement range. The output signal therefore will be updated periodically.
From the beginning of the measurement till the end of the first measurement interval the output
current value equals 4mA.
The maximal current value of 20mA corresponds to the value of ten times the Radon alarm
threshold. In the case of threshold value of 300Bq/m3(default setting) the 20mA output current
represents the Radon value of 3000Bq/m3. For Radon activity below detection limit the 4mA current
value will be held. The output signal of the current loop is realized with 12-bit digital/analog
converter. As a result the resolution of the output signal is equal to 0,0039mA.
Example:
The current output value will be set according to a following calculation with a Radon threshold of
300Bq/m³ and the Radon measurement equal to 1125Bq/m³:
IOUT = { 1125Bq/m³ • ( 20mA – 4mA ) } / { 10 • 300Bq/m³ } + 4mA = 10mA.
20mA output signal will be present for all measurement results above Radon range defined for the
current loop (10 •Radon alarm threshold). The relationship between Radon alarm threshold and the
output range of the analogue signal allows for easy adjustment to the input range of the data
acquisition system.
Warning: If Smart Radon Sensor is being integrated in existing network or measurement system, first
an apparent resistance has to be considered. The entire apparent ohmic resistance ought not to be
greater than 475Ohm for 12V supply voltage. For 24V supply voltage the apparent resistance must
not excide 1075Ohm.
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Alert switch
The Smart Radon Sensor is equipped with a switch output which can be used for ventilation control
or alert indication. The potential-free contacts of the switch will be short-circuited at the end of the
sampling interval if the measured Radon concentration exceeds the alarm threshold. The output will
be deactivated one minute before the subsequent interval ends. Therefore, the sampling interval
must be set at least to two minutes. The alarm threshold is factory-set to 300Bq/m³ (statutory
reference value of the Radiation Protection Act) and may be changed by the user with respect to
local regulations (instrument setup in Radon Vision). Warning: at the same time the alarm threshold
defines the Radon range for the maximal output signal of the current loop. Please refer to the
previous chapter: „Analogue output”.
The terminal ports for the alert switch are designated in figure 2 and table 1.
As an accessory, we offer a wireless power switch which can be used for direct ventilation control.
The switch includes a transmitter unit to be connected to the alert switch output of the instrument,
and a plug adaptor (receiver) which can be placed between the wall outlet and the power cable of
the ventilation unit. Optionally, a flush-mounting power switch is also available. The plug adaptor
offers an additional timer function to define the duration of the ventilation period independent from
the sampling interval of the instrument (for example 15 minutes ventilation while the sampling
interval is 60 minutes long). The wireless switch is coded - that means, several transmission lines can
be established within one building. The assignment between transmitter and receiver is easily done
by a push button.
The sampling interval should be set to a value between 60 or 120 minutes for an alarm threshold
lower than 300Bq/m³.
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Supplementary equipment
According to the needs of the customer the Smart Radon Sensor can be equipped with additional
sensors for example: pressure or CO2 sensor.
Pressure sensor
The barometric pressure can be measured in a range from 800mbar to 1200mbar. The sensor unit is
fully calibrated and features temperature compensation.
CO2gas sensor
The integrated CO2 sensor uses the non-dispersive infrared (NDIR) operational principle. This
requires an infrared source which cannot be supplied by the internal batteries due to the increased
power consumption. Therefore CO2 sensor works only if external power supply is present.
Continuous operation
The automatic calibration procedure of the sensor uses the CO2 concentration of fresh air (400ppm)
as reference. The instrument must be exposed to this “fresh air concentration” at least once during
the last 24 hours. This can be achieved by short ventilation of the room. If there are no persons
inside a room for a while (for example overnight), the concentration goes back to 400ppm.
Attention! If the reference concentration cannot be reached within the past 24 hours, the sensor
interprets the lowest measured result as 400ppm. This results in a systematically increasing
measurement error.
If the CO2 concentration exceeds the recommended threshold of 1000ppm, the yellow LED turns on.
It will turn off as soon as the concentration drops below 1000ppm.
Occasional operation
If the CO2sensor is used for sampling periods less than 24 hours no calibration procedure as
described above is carried out. Therefore it is recommended to operate the sensor at least once per
week for a period longer than 24 hours to force a calibration. Of course, the instrument must be
exposed to the fresh air concentration of 400ppm during that time.
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Disposal instructions
Batteries and accumulators must not be disposed of in the garbage, but you are legally obligated to
return them to the appropriate waste collection centers. The measuring instruments must be
disposed of in the electronic waste or handed to the manufacturer at the end of their service life for
proper disposal. If necessary, they have to be decontaminated before.
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Technical data
Smart Radon Sensor
Radon measurement
Operational principal
Lucas cell with gross alpha counting
Sampling method
Diffusion
Sensitivity
> 2,5cpm/(kBq/m³)
Range
1 ... 1MBq/m³
Uncertainty (1)
1 hour @ 300Bq/m³
1 day @ 300Bq/m³
1 day @ 50Bq/m³
15%
3%
8%
Ambient
-10°C ... 50°C, 0%rF ... 100%rF non condensing
Humidity
Range
0%rH … 100%rH
Accuracy
< 4,5%rH (3% typ.) for 20%rH … 80%rH
Temperature
Range
-40°C … 120°C
Accuracy
< 0,4°C (0,3°C typ.) for 5°C … 60°C
Pressure 1)
Range
760mbar ... 1200mbar
Accuracy
< 0,5% FSO
CO2Sensor1)
Principle of operation
Non dispersive infrared (NDIR)
Range
400ppm … 5000ppm
Accuracy
< 5% ± 50ppm
Response time
10min
Remark
Automatic calibration with respect to outdoor CO2 level
1) Available as an option
Table of contents
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