LSI LASTEM DMA867 User manual

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Thermo-hygrometer
with current outputs
cod. DMA867 and DMA875
User manual

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Index
1Introduction...................................................................................................................................3
1.1 Notes about this manual........................................................................................................3
2Product installation.......................................................................................................................4
2.1 General safety rules...............................................................................................................4
2.2 How to choose the survey site...............................................................................................4
2.3 Mechanical mounting............................................................................................................5
2.4 Dip-switches configuration ...................................................................................................5
2.5 Electrical connection.............................................................................................................5
3Application note............................................................................................................................6
3.1 Measuring humidity in high temperature environments .......................................................6
4Diagnostics ...................................................................................................................................7
4.1 External visual check.............................................................................................................7
4.2 Internal visual check..............................................................................................................7
5Maintenance..................................................................................................................................8
5.1 Cleaning the antiradiant shield..............................................................................................8
5.2 Cleaning the measuring elements and the porous filter ........................................................8
6Accessories / Spare parts..............................................................................................................9
7Disposal ........................................................................................................................................9
8How to contact LSI LASTEM......................................................................................................9
9Specifications..............................................................................................................................10
9.1 Models.................................................................................................................................10
9.2 Measuring specifications.....................................................................................................10
9.3 Signal outputs specifications...............................................................................................11
9.4 Electrical specifications.......................................................................................................11
9.5 Mechanical specifications ...................................................................................................11
9.6 General specifications .........................................................................................................11
10 CE conformity declaration..........................................................................................................12

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1Introduction
Thermohygrometers DMA867 and DMA875 are instruments to measure environmental
temperature, relative humidity and dew point. The determination of dew point takes place
according to the formulations specified by ISO 7726.
The measuring element is housed inside a radiation shield, available with both natural (DMA875)
and forced (DMA867) ventilation, to achieve measuring conditions equivalent to a Stevenson
shelter.
1.1 Notes about this manual
Document: INSTUM_01378_en - Update on 9 Mar. 2015.
The information contained in this manual may be changed without prior notification. No part of this
manual may be reproduced, neither electronically or mechanically, under any circumstance, without
the prior written permission of LSI LASTEM.
LSI LASTEM reserves the right to carry out changes to this product without timely updating of this
document.
Copyright 2015 LSI LASTEM. All rights reserved.

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2Product installation
2.1 General safety rules
Please read the following general safety rules in order to avoid injuries to people and prevent
damages to the product or to possible other products connected with it. In order to avoid any
damages, use this product exclusively according to the instructions herein contained.
The installation and maintenance procedures must be carried-out only by authorized and skilled
service personnel.
Power the instrument in a suitable manner. Pay attention and observe the power supplies like
indicated for the model in your possession.
Carry-out all connections in a suitable manner. Pay strict attention to the connection diagrams
supplied with the instrument.
Do not use the product in case of suspected malfunctions. In case of suspected malfunction, do not
power the instrument and contact authorized technical support immediately.
Do not set working the product in an explosive atmosphere.
Before you carry-out any operation on electrical connections, power supply system, sensors and
communication apparatus:
Disconnect the power supply.
Discharge the accumulated electrostatic discharges touching an earthed conductor or
apparatus.
2.2 How to choose the survey site
Select a site with conditions representative of the environment being examined. Thermo-
hygrometers must be assembled in sites where the morphological conditions of the earth, the urban
structures and the environmental conditions in general make them particularly representative of the
general conditions in which the measurement is to be performed.
It is important that there are no structures in the nearby areas which might radiate heat, such as
cement floors, asphalt, walls, etc. The thermo-hygrometers should be installed at 1.5 - 2 m from the

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2.3 Mechanical mounting
Fit the DYA049 or DYA051 supporting collar to the
pole at the desired height, usually at 1,5 - 2 m, and
tighten the screws using an allen key n. 6.
Fix the sensor to the supporting collar by tightening
the two bolts indicated with arrows in the picture.
Connect the DWA cable to the sensor and to the data
acquisition system according to drawing
DISACC5901d.
when a forced ventilation radiation shield is in use,
feed the fan engine with a suitable power supply.
2.4 Dip-switches configuration
The factory settings are:
Electric output: 4÷20 mA
Hygrometric output: UR %
Temperature range: -30÷70 °C
To change the settings open the sensor box , set the dip-switches according to your needs (the
arrangement of the dip-switches is shown inside the box cover and on the drawing DISACC5901d)
and close the box.
2.5 Electrical connection
Power the instrument according to the technical specifications. For optimal operation, ensure proper
earthling of the power and communication lines.

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3Application note
3.1 Measuring humidity in high temperature environments
In very wet tropical areas, humidity values may acquire a very low dynamic range, close to
saturation conditions and, at the same time, to have a low temperature dynamic range and very low
wind speed values. In certain periods of the year, these conditions may occur even in milder areas
for short periods of time.
In such conditions, the hygrocapacitive element can get wet (from dew) and have no time to get dry
and restore its measuring capacity. In this case, even if the humidity value decreases, the humidity
measurement stabilizes to the saturation value or is –at any rate –underestimated.
Two conditions may occur. The first one refers to every category of “exchange type” humidity
sensor; the second one is typical of capacity-measurement humidity sensors:
a) The layer of dew over the measuring element can reach 0,25 mm. Penman’s theory states that
8 hours are needed for the layer of dew to evaporate (30°C, 80 RH% with no air speed), or 4
hours (30°C, 60 RH% with no air speed). These time periods can be shorter in case of forced
ventilation (not less than 1.5 m/s).
b) The manufacturers of hygrocapacitive elements inform that a persistent humidity level on the
element could produce a secondary absorption phenomenon, as well as cause a temporary shift of
the humidity measurement equal to about +6%. This error disappears when theelement is exposed
for some hours to lower humidity values.
These considerations confirm that the hygrocapacitive element can be used when humidity values
reach a sufficient dynamic range to enable the sensor adjustment based on the “stress” condition.

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4Diagnostics
4.1 External visual check
1. Check that the external anti-radiant shield is clean and with no dents (a suitably clean shield
will have a higher reflecting capacity).
2. Check for the fan (in the forced ventilation models) proper operation.
4.2 Internal visual check
Draw out the sensor from the shield and:
1. Check that the porous filter protecting the sensitive element is properly clean (see §5.2).
2. Check that the hygrocapacitive element is properly clean. Check for any presence of dust or
dew on the capacitive plate (if possible also with the help of a magnifying lens). Check as
well that contacts are free from oxidations. Do not touch the capacitive plate with your hands.
If necessary, clean the element (see §5.2).

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5Maintenance
This sensor is a precision measurement apparatus. In order to maintain the specified measurement
precision over the time, LSI LASTEM recommends check it periodically (at least twice a year); it is
moreover suggested the replacement of the measure element according to the place of installation
(in persistent conditions of high humidity, pollution, dust and chemical substances presence, the
sensitive element deteriorate faster than the one placed in a location with less adverse conditions). It
is, anyway, a good rule to replace the sensitive element at least once every two years.
Please, remind that the sensitive element ML3015, when used, is no under guarantee.
5.1 Cleaning the antiradiant shield
Clean the external anti-radiant shield with the aid of a small brush or a wet rag.
5.2 Cleaning the measuring elements and the porous filter
1. Disconnect the cable from the probe;
2. Unscrew the cable seals at the bottom and pull out the sensor from the shield;
3. Unscrew the filter;
4. Clean the filter with a cold air jet.

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6Accessories / Spare parts
Code
Description
DYA049
Mast-mounting device for Ø45÷65 mm pipe
DWA510
Cable L = 10 m
DWA525
Cable L = 25 m
DWA526
Cable L = 50 m
DWA527
Cable L = 100 m
ML3015
Sensitive element (spare part)
MM0315
Fan for forced ventilation shield DYA231 (12 Vdc)
MM0316
Fan for forced ventilation shield DYA232 (24 Vac)
DZC301.S
Calibration certificate
MG2251
7 pin free female connector.
7Disposal
This product is a device with high electronic content. In accordance with the standards of
environmental protection and collection, LSI LASTEM recommends to handle this product as waste
of electrical and electronic equipment (RAEE). For this reason, at the end of its life, the instrument
must be kept apart from other wastes.
LSI LASTEM is liable for the compliance of the production, sales and disposal lines of this
product, safeguarding the rights of the consumer. Unauthorized disposal of this product will be
punished by the law.
8How to contact LSI LASTEM
In case of problem contact the technical support of LSI LASTEM sending an e-mail to
[email protected], or compiling the technical support request module at www.lsi-lastem.it.
For further information, refer to addresses and numbers below:
Phone number: +39 02 95.414.1 (exchange)
Address: via ex S.P. 161 –Dosso n. 9 - 20090 Settala Premenugo, Milano
Web site: www.lsi-lastem.it
Commercial service: [email protected]
After-sales service: [email protected], [email protected]

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9Specifications
9.1 Models
Order numb.
DMA867
DMA875
9.2 Measuring specifications
Measures:
oAmbient temperature [°C]
oAmbient relative humidity [%]
oAmbient dew point [°C]
Ambient temperature section:
oPrinciple: Pt100 thermoresistance
oRange: selectable from
Variant .1:
-30 ÷ 70 °C
-50 ÷ 100 °C
-50 ÷ 50 °C
0 ÷ 100 °C
Variant .2:
-40 ÷ 60 °C
-50 ÷ 60 °C
-50 ÷ 70 °C
-30 ÷ 100 °C
oAccuracy: ±0.2 K @ 23 °C
oResolution 0.04 °C
oResponce time: 3' (T90)
Humidity section:
oPrinciple: hygro-capacitive
oRange: 0 ÷ 100 %rh
oAccuracy ±1.5 %rh @ 23 °C
oResolution 0.1 %rh
oResponce time: 10' (T90)
Dew point section:
oMeasurement calculated conforming to ISO 7726 formulas
Other characteristics:
oForced ventilation (only DMA867)