4
The 3½ digit LED display normally indicates the current
differential pressure. The backlit symbols to the right of
the 3½ digit LED display indicate the unit of pressure me-
asurement. (Note: the units shown in the illustrations of
this document can be different from those of the actual
instrument). The two LED lamps above the 3½ digit LED
display respectively indicate the status of the two limit re-
lays / solid-state switches
(LED on = relay contacts
closed / solid-state switch on).
While the instrument is in set-up mode, the 3½ digit LED
display either indicates the selected menu option or a
set-up parameter value. The instrument continues its
pressure monitoring functions even while it is in set-up
mode, except under either of two circumstances.
One is when the limit switching delay time is changed:
the existing delay must time out first. The other is when
the look-up table (for conversion of measured values) is
re-programmed (s. 5.3.7.). In these circumstances, the
output signal value and the limit relay/switch states are
frozen until the changes are finalized.
5.3.
Set-up
The instrument has comprehensive set-up options by
means of which it can be optimized for any specific mea-
suring or control application. This section of the
document provides information and instructions about
each of the set-up parameters.
Depending on the instrument configu-
ration ordered (e.g.: without transmitter
signal output / with voltage signal out-
put / with current signal output) some of
the menu options may not available.
Some set-up parameters may be consequentially exclu-
ded. For example, if the instrument is ordered without a
transmitter output, all signal conversion programming op-
tions are omitted in the set-up menu (s. 5.3.6. Signal
Conversion and Transfer Functions).
All instrument settings can be conveniently done from a
PC connected to the instrument through a serial interface
adaptor. All set-up parameters can be viewed and
changed on the PC screen. Also, the entire instrument
set-up configuration can be loaded, stored on the PC's
hard disk drive, and printed out for plant / process
documentation purposes. Further information about this
PC software is given in the software documentation.
5.3.1. Selecting the Unit of Pressure Measurement
Make the necessary electrical connections (signal, pow-
er supply) to the instrument. Its pressure sensor must be
pressure-free (i.e. vented to atmosphere; typically by
disconnecting the pressure line/s).
The current valid unit of measurement is indicated by one
of the back-lighted symbols to the right of the digital dis-
play. To change the unit of measurement, first press
û
then search for parameter
EIN
using
þ
. Next press
û
again and select another unit of measurement using
þ
or
ÿ
. Then presse again
û
to store the selection, and
EIN
will appear again in the digital display.
To exit the set-up mode, press
ÿ
until
ESc
appears, and
then press
û
. The current pressure measured value is
indicated again, and the appropriate symbol of the unit of
measurement (to the right of the digital display) is lighted.
The digital display is limited to a count
of ±1999. Therefore, all the available
units of measurement may not be su-
itable for selection for a given applica-
tion.
5.3.2. Zero Point Checking and Adjustment
If the instrument has been de-pressurized (vented to at-
mosphere) and does not indicate precisely zero, note this
non-zero value. Using the set-up parameter
OF1
, you can
trim this offset to exactly zero. If the indicated non-zero
value is positive, this value must be entered and stored
as a negative offset value, and vice versa.
If the instrument was in use before zero
setting is done, values of set-up
parameters
OF1
and
nP
would have
been previously programmed. In this
case, set both values to zero, read the
actual zero offset, and then use this value for
OF1
for zero
point correction, as described in the previous paragraph.
Note: The registered value is a pure number: no decimal
point is indicated.
After correcting the zero offset, the pressure connections
can be made again.
5.3.3. Damping and Zero Stabilization
If the media is subject to excessive pressure fluctuations,
the displayed readings and the transmitter output signal
can be stabilized using the instrument's
DAM
and
NP
set-
up parameters.
The set-up parameter
DAM
has the effect of a pulsation
damper (on the displayed measurements, output signal
and limit detection, - not on the sensor itself!). It adds a
time-constant (averaging filter) in the user selectable
range of 0.0 to 100.0 secs. When the damping is set to
maximum, it took more than 2 minutes to reach the final
value for a full scale pressure jump.
In many cases fluctuating pressure readings do not cau-
se a problem, except when the plant / equipment is at
zero (differential) pressure condition and readings fluctu-
ate near about zero value. The set-up parameter
NP
is
meant to take of this. Its value defines the number range
across zero (similar to the zero offset correction number),
within which the measured value is forced to zero. If a
value of 8 is set for
NP
any pressure measurement in the
range -0.08 to +0.08 bar (or -8 to +8 kPa) displayed as
Contact: EK Engineering (India)
Web: www.ekeindia.com
Email: [email protected]
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