Lumel P18S User manual

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TEMPERATURE
AND HUMIDITY TRANSDUCER
P18S
USER’S MANUAL

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Contents
1. APPLICATION............................................................................... 5
2. TRANSDUCER SET ..................................................................... 6
3. BASIC REQUIREMENTS, OPERATIONAL SAFETY..................... 6
4. ASSEMBLY................................................................................... 6
4.1. INSTALLATION....................................................................... 6
4.2. EXTERNAL CONNECTIONS DIAGRAM ............................... 8
5. OPERATION ................................................................................. 9
5.1. TRANSDUCER FUNCTIONS............................................... 10
5.1.1. CALCULATED VALUES .................................................... 10
5.1.2. OPERATION OF THE INTERNAL HEATER...................... 12
5.1.3. SERIAL INTERFACE CONNECTION METHOD ................... 12
5.1.4. DESCRIPTION OF MODBUS PROTOCOL IMPLEMENTATION... 13
5.1.5. DESCRIPTION OF IMPLEMENTED FUNCTIONS ........... 14
5.1.6. MAP OF REGISTERS ....................................................... 15
5.1.7. READ-ONLY REGISTERS ............................................. 16
5.1.8. REGISTERS FOR WRITING AND READING ................. 17
6. ACCESSORIES .......................................................................... 21
7. TECHNICAL DATA ..................................................................... 22
8. ORDERING CODE...................................................................... 23

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1. APPLICATION
The P18S transducer is designed for continuous measure-
ment and conversion of relative humidity and ambient temperature into
a digital form (MODBUS RTU protocol via the RS-485 interface). Trans-
ducer configuration is possible using the MODBUS protocol.
Values measured and calculated by the transducer:
• temperature,
• relative humidity
• dew point
• absolute humidity
Fig.1. View of P18S transducer.

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2. TRANSDUCER SET
−P18S transducer 1 pc.
−User’s manual 1 pc.
3. BASIC REQUIREMENTS,
OPERATIONAL SAFETY
In terms of operational safety, the transducer meets the requi-
rements of EN 61010-1 standard.
4. ASSENBLY
4.1. Installation
The transducer should be mounted in a safe manner using ge-
nerally available assembly elements, such as cable glands and cable grom-
mets, clamps, cable ties enabling access when service works are needed
(e.g. cleaning in the event of soiling affecting the device operation, replace-
ment in the case of damage). It is important to ensure the transducer wor-
king position so that its measuring sensor is directed downwards. Electrical
connections should be made in accordance with the transducer connection
diagram.
Safety instructions
• The assembly and the installation of the electrical connections may
be carried out only by a duly qualified electrician.
• Before turning the transducer on verify the connections.
• The transducer is intended for installation and use in industrial electro-
magnetic environments.

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Fig.2. External dimensions of P18S
min. 50mm
R20
83
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4.2. External connections diagram
The transducer has a 4-wire non-detachable cord which is 2.5 or 10m
long or a detachable M8 socket with a 2-meter long wire (depending on
the version code) used for supplying and connecting the RS-485 inter-
face:
Table 1: Transducer terminals
non-detachable cord
(color of the cord)
M8 socket
(terminal number)
cable with M8 plug
(color of the cord)) Function
green 3 blue Positive power cordVCC
yellow 1 brown Negative power cord GND
brown 4 black RS-485 “B”signal
white 2 white RS-485“A”signal

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5. OPERATION
After wiring and turning on the power supply, the transducer is
ready for operation with the factory settings. Operation of the transducer
is signaled by a short, repeatable illumination of the yellow LED located
under the sensor cover.
The transducer can be configured by recording MODBUS RTU pro-
tocol registers on the RS-485 interface.
The following parameters can be programmed in the transducer:
−device address for MODBUS RTU protocol
−RS-485 interface baud rate
−RS-485 interface communication mode
−measurements averaging mode
−erasing the saved values of extreme measurements
−switching on/off the internal heater
−setting the heating time with the internal heater in time mode
−fixed correction for temperature measurement
Through dedicated registers, it is also possible to restore the trans-
ducer factory parameters and force the recording of current operating
parameters into the non-volatile memory of the transducer.
CAUTION: In case when unknown transmission parameters are set
in the transducer, it is possible to force the transducer communication
according to the standard parameters (9600, 8N1). To do this:
−turn off the transducer power supply
−remove the sensor cover
−short together the soldering points in accordance with figure 2
−turn on the transducer power supply (the LED will be solid yellow)
−remove the short circuit (yellow LED goes out)

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Fig.3. Setting the standard communication parameters
At this point, it is possible to connect to the transducer and configure it
according to user’s requirements and then save the configuration to the
non-volatile memory.
If the configuration is not saved, the previous configuration will be
active after restarting the transducer and the procedure will have to be
repeated.
5.1. Transducer functions
The P18S transducer performs the following functions:
• measurement of the ambient temperature and relative humidity,
• calculation of selected physical quantities,
• recording the maximum and minimum values (extremes) in volatile
memory,
• RS-485 interface support in MODBUS protocol in RTU mode.
5.1.1. Calculated values
The P18S transducer calculates the dew point and absolute humidity va-
lues on the basis of the temperature and relative humidity measurement
from the following relationships.
DP = Tn
m-1
log (Pws RH
10000  A
)
DP→dewpoint: