4
ment). The two LED lamps above the 3½ digit LED dis-
play respectively indicate the status of the two limit relays
/ solid-state switches
(LED on = relay contacts clo-
sed / 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. 5.3.8.). 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
measuring or control application. This section of the do-
cument 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. 5.3.7. 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 chan-
ged 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 related manual.
5.3.1. Selecting the Unit of Pressure Measurement
Make the necessary electrical connections (signal, po-
wer supply) to the instrument. Its pressure sensor/s 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 backlit symbols to the right of the digital display. 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 press 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 lit.
The digital display is limited to a count
of ±1999. Therefore all the available
units of measurement may not be suit-
able for selection for a given appli-
cation.
5.3.2. Display Settings
Because the DE44 has two independent measuring
channels, a user can command the instrument to display
any one channel continuously, or both alternating. For
this, the
dSP
parameter is set to either the first channel
(
dSP
= 0.0) or the second channel (
dSP
= 0.1), or both
channels alternating with a user-programmable display
time for each channel (
dSP
= 0.2 to 99.9 secs per chan-
nel). The backlit symbols P1 and P2 to the left of the di-
gital display indicate which channel's measurement is
currently displayed.
Setting a channel display time of about 3 seconds gives
the user sufficient time to comfortably read the measure-
ment, yet avoid the need to manually switch the display
between P1 and P2.
5.3.3. 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 para-
meters
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.
Because the DE44 has two independent measuring
channels, zero offset correction has to be made for the
second channel (
OF2
) exactly in the same way as for the
first (
OF1
).
5.3.4. 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
Contact: EK Engineering (India)
Web: www.ekeindia.com
Email: [email protected]
