No part of this manual may be reproduced, published or publicly displayed in any form
or by any means, electronic or mechanical (including photocopying), nor may its
contents be modified, translated, adapted, sold or disclosed to a third party without prior
written permission of the copyright holder. Translated manuals and translated portions
of multilingual documents are based on the original English versions. In ambiguous
cases, the English versions are applicable, not the translations.
The contents of this manual are subject to change without prior notice.
This manual does not create any legally binding obligations for Vaisala towards
customers or end users. All legally binding obligations and agreements are included
exclusively in the applicable supply contract or the General Conditions of Sale and
General Conditions of Service of Vaisala.
requirement when using the Modbus protocol.
Added a packing recommendation for return
Related Manuals
Table 2 Related Manuals
Documentation Conventions
WARNING
CAUTION
NOTE
Throughout the manual, important safety considerations are highlighted
as follows:
Warning alerts you to a serious hazard. If you do not read and follow
instructions very carefully at this point, there is a risk of injury or even
death.
Caution warns you of a potential hazard. If you do not read and follow
instructions carefully at this point, the product could be damaged or
important data could be lost.
Note highlights important information on using the product.
Chapter 1 _________________________________________________________ General Information
Ground the product and verify outdoor installation grounding
periodically to minimize shock hazard.
Do not
or lead to malfunction.
Do not drop or hit the transmitter. The sensor is fragile and may break
from a sudden shock.
When transporting the transmitter, use the original shipping box
Vaisala.
Do not open the connection between the adapter and the transmitter.
They are connected at the factory, and the connection should remain
unopened to guarantee tightness.
Use tools only on the nut of the adapter, where the transport p
cap is connected.
Keep the transmitter dry and clean.
Do not remove the yellow transport protection cap before you are ready
to install the transmitter. Uncapped transmitters will absorb moisture
which will affect the dewpoint measurement.
Connect the transmitter directly to the main SF
a sampling line.
After installation, the transmitter will have a small amount of moisture
inside it. In still, dry gas it takes a long time until vapor pressure inside
the measurement cell reaches equilibrium with the main gas tank. It is not
unusual for the stabilization
after installation.
Safety
The DPT145 transmitter delivered to you has been tested for safety and
approved as shipped from the factory. Note the following precautions:
WARNING
CAUTION
CAUTION
CAUTION
NOTE
modify the unit. Improper modification can damage the product
Electrostatic Discharge (ESD) can cause immediate or latent damage to
electronic circuits. Vaisala products are adequately protected against
ESD for their intended use. It is possible to damage the product,
however, by delivering electrostatic discharges when touching,
removing, or inserting any objects inside the equipment housing.
To make sure you are not delivering high static voltages yourself:
- Handle ESD sensitive components on a properly grounded and
protected ESD workbench.
- When an ESD workbench is not available, ground yourself to the
equipment chassis with a wrist strap and a resistive connection cord.
- If you are unable to take either of the above precautions, touch a
conductive part of the equipment chassis with your other hand before
touching ESD sensitive components.
- Always hold component boards by the edges and avoid touching the
component contacts.
Recycling
Recycle all applicable material.
Dispose of the unit according to statutory regulations. Do not dispose of
with regular household refuse.
This product contains software developed by Vaisala. Use of the software
is governed by license terms and conditions included in the applicable
supply contract or, in the absence of separate license terms and
conditions, by the General License Conditions of Vaisala Group.
Warranty
Visit our Internet pages for more information and our standard warranty
terms and conditions: www.vaisala.com/warranty.
Please observe that any such warranty may not be valid in case of
damage due to normal wear and tear, exceptional operating conditions,
negligent handling or installation, or unauthorized modifications. Please
see the applicable supply contract or Conditions of Sale for details of the
warranty for each product.
Dewpoint/frost point temperature*,
converted to atmospheric pressure
Tdfatm
ºC
ºF
ppm moisture, by volume
H20
ppm
ppm
Pressure, absolute
P
bara
psia
Pressure, normalized to 20 °C
(68 °F)
Pnorm
bara
psia
Density
Rhoo
kg/m3
kg/m3
Temperature
T
ºC
ºF
CHAPTER 2
PRODUCT OVERVIEW
This chapter introduces the features, advantages, and the product
nomenclature.
Introduction to DPT145
Vaisala Multiparameter Transmitter DPT145 for SF6 Gas is a digital
transmitter with a non-isolated RS-485 output. Its compact size makes it
well suited for integration into OEM systems.
DPT145 is always delivered with an integrated mechanical adapter:
DILO DN20, DILO DN8, ABB Malmkvist, or Alstom G1/2". The
connection between the adapter and the transmitter is helium leak tested
at the factory.
DPT145 combines online measurement of dewpoint, pressure, and
temperature. DPT145 also calculates four other quantities, including SF6
density.
Table 3 Output Parameters of DPT145
* When the dewpoint is below 0 °C, the transmitter outputs frostpoint for Td
The transmitter and its connectors are rated IP65. However, installing the
transmitter outside without protection is not recommended. The
installation should be such that the transmitter is not exposed to direct
rain, icing, or solar radiation.
A suitable weather shield is available from Vaisala. The weather shield is
designed to clamp over the adapter, and to accommodate the available
cable options.
1108-022
Figure 3 Weather Shield
DPT145 is assembled to the weather shield at the factory if the weather
shield is ordered with the transmitter. Weather shields are also available
separately.
This chapter describes the primary application and the sensor technology
of DPT145.
Measurement Needs of SF6 Insulation
Sulphur hexafluoride (SF6) is used as an insulating gas in transmission
and distribution equipment such as switchgears and circuit breakers. It
effectively prevents arcing during switch-offs and protects equipment
from failures.
In order to maintain SF6 insulation properties and to reduce the formation
of unwanted secondary decomposition products, the amount of water
vapor in the gas insulated system (GIS) should be kept to a minimum.
Also, the SF6 system needs to be pressure tight for best insulation
performance and safe operation of the equipment.
There is always some diffusion of water molecules from high ambient
water vapor pressure to low vapor pressure inside the system. The more
connection points the higher the diffusion rate. DPT145 is ideally suited
to the online monitoring of dewpoint, pressure, and temperature in such a
system. Sudden and minor leakages are immediately detected by the
direct normalized pressure measurement, while online dewpoint
measurement alerts the user to moisture issues.
With online monitoring, on-site visits can be kept to a minimum. The
long calibration interval of DPT145 means practically service-free
operation.
DPT145 combines Vaisala’s proven DRYCAP® sensor technology for
industrial dewpoint measurement with BAROCAP® pressure sensor
technology. Both technologies are integrated on the same MPS1
multiparameter sensor element, allowing for a highly compact and
versatile transmitter.
1108-021
Figure 4 MPS1 Sensor
There are several important advantages in using a transmitter with an
integrated sensor:
- Reduces installation work and cost.
- Improves the leak tightness of the system as connection points are
minimized.
- Enables online monitoring of all supported parameters.
DRYCAP® Technology
Vaisala DRYCAP® dewpoint measurement technology ensures accurate
measurement with excellent long term stability. This results in very low
maintenance requirements for the transmitter. The lasting performance is
achieved with microprocessor technology and software that automatically
performs self-diagnostic functions in addition to the normal dewpoint
measurement. The self-diagnostic procedures that are conducted are
called auto-calibration and sensor purge.
The auto-calibration feature of the MPS1 multiparameter sensor is an
automatic procedure which greatly reduces the possible drift in the dry
end of the dewpoint measurement. It is performed at one hour intervals,
and when the power is switched on. During auto-calibration the sensor is
warmed for a short period (< 1 min) and the sensor capacitance values
are evaluated at the elevated temperature. The possible dry end drift is
then corrected to correspond to the calibrated values. During the autocalibration the transmitter outputs the dewpoint value prior to the
procedure.
Auto-calibration is carried out only if several criteria for the
measurement environment are fulfilled. This ensures the reliability of the
adjustments, and maintains the excellent long term stability. These
criteria include, for example, a stable enough moisture level in the
measured atmosphere. If the conditions are not fulfilled, the autocalibration function is postponed until satisfactory conditions are
reached.
Sensor Purge
Sensor purge is also an automatic procedure that minimizes the drift at
the wet end readings of the dewpoint measurement. Sensor purge is
performed twice a day, and five minutes after the power is switched on.
The sensor is heated for several minutes which will then evaporate all
excess molecules out of the sensor polymer. This, together with the autocalibration, results in a very small drift of the sensor due to the very
linear behavior of the polymer technology.
BAROCAP® Technology
The BAROCAP® silicon capacitive absolute pressure sensor was
developed by Vaisala for barometric pressure measurement applications.
The BAROCAP® sensor has excellent hysteresis and repeatability
characteristics, low temperature dependence, and a very good long-term
stability. The ruggedness of the BAROCAP® sensor is outstanding and
the sensor is resistant to mechanical and thermal shocks. The pressure
measurement of the MPS1 multiparameter sensor is based on an
advanced RC oscillator and reference capacitors against which the
capacitive pressure sensor is continuously measured. The microprocessor
of the transmitter performs compensation for pressure linearity and
temperature dependence.