WIKA DA10 - Manual (Page 2)

INSTRUCTION MANUAL
NI-209E
Rev. 4 12/02
1. GENERAL
NOTES
1.1 FOREWORD
The wrong choice of a series or a model, as well as the
incorrect installation, lead to malfunction and reduce
instrument life. Failure to follow the indications given in
this manual can cause damage to the instrument, the
environment and persons.
1.2 ALLOWED OVERRANGE
Pressures exceeding the working range can be
occasionally tolerated provided they remain within the
limits stated in the instrument features (vacuum or proof
pressure). Continuous pressures exceeding the
working range can be applied to the instrument,
provided they are clearly stated in the instrument
features. The current and voltage values stated in the
technical specifications and ratings must not be
exceeded. Transitory overranges can have a destructive
effect on the switch.
1.3 MECHANICAL VIBRATIONS
Can generally lead to the wearing of some parts of the
instrument or cause false actuation. It is therefore
recommended that the instrument be installed in a place
where there are no vibrations. In cases where this is
impossible it is advisable to take measures to lessen the
effects (elastic supports, installation with the pin of the
microswitch positioned at right angles to the vibration
plane, etc.).
1.4 TEMPERATURE
Due to the temperature of both the environment and the
process fluid, the temperature of the instrument could
exceed the allowed limits (normally from -20° to +70°C).
Therefore, in case it does, suitable measures (protection
against heat radiation, fluid separators, cooling coils,
heated lockers) must be taken. The process fluid or its
impurities must not in any case solidify inside the
instrument chambers.
2. OPERATING
PRINCIPLE
The differential pressure, acting on the sensitive
diaphragm element, determines its elastic deformation
which is used to actuate one or two electric
microswitches regulated at set point values. The
microswitches are of the snap acting type with automatic
reset. When the pressure moves away from the set
values, returning towards the normal values, the switch
is reset. The dead band (difference between the set
point value and the reset value) can be set or adjustable
(letter R in the contact codes).
3. IDENTIFICATION PLATE AND MARKINGS
The instrument is fitted with a metal plate bearing all its
functional characteristics and – in case of
explosionproof execution (Series DA) – also the
markings prescribed by standard CEI EN 50014. Fig. 1
shows the plate mounted on explosionproof instruments.
Fig. 1 - Explosionproof instruments plate
1 CE marking and identification number of the notified body
responsible for production surveillance.
2 Apparatus classification according to ATEX 94/9 CE
directive.
3 Type of protection and ambient temperature limits of
operation.
4 Notified body that issued the type certificate and number of
said certificate.
4. SET POINT REGULATION
Each microswitch is independent and can be regulated
by means of a screw (for adjustment) in such a way that
it is released when the pressure reaches (increasing or
decreasing) the desired value (set point).
The instrument is usually supplied with the switches set
at the setting range value nearest to zero (factory
calibration).
The instrument is supplied with an adhesive rating plate
showing the set point calibration value. With factory
calibration the values are not indicated on the ratings
as these are temporary and will be modified with the
definitive values.
Prior to installation the instrument must be calibrated
and the definitive calibration values written on the
adhesive rating plate using a suitable indelible ink pen.
If the instrument has been ordered with a specific
calibration, it is a good rule to check the calibration
values marked on the relevant adhesive label, prior to
installation.
The position of the adjustment screws is given in fig. 2.
The effect that the direction of rotation of the adjustment
screws has is described on the adhesive plate.