FISCHER DE44 Скачать руководство пользователя страница 5

Страница: 5 / 16

Once the value has been selected, save it with

and

EIN

will appear again in the display.

Then leave the setting mode. Press

until

Esc

and

the

appear. The current measured pressure is

shown again. The correct pressure unit is now illu-
minated to the right of this.

The display can only show up to ±1999.
Therefore in some cases it may not be
possible to select all stated pressure
units.

5.3.3

Display settings

Due to the fact that the DE44 has two independent
pressure measuring systems but only one display,
you can use the

dSP

parameter to select whether

you want to have only the first channel (

dSP

= 0.0),

only the second channel (

dSP

= 0.1) or both chan-

nels alternately (

dSP

= 0.2 to 99.9) displayed. From

0.2 s upwards,  the value simply  determines the re-
tention period (0.2 s to 99.9 s per channel). So that
it  is  clear  which  value  is  currently  being  displayed,
the  symbols  P1  for  the  1st  channel  and  P2  for  the
2nd channel are shown accordingly on the left edge
of the display.

It is advisable for the other settings to in-
itially select a slow switching time (e.g. 3
s). This saves you the effort of having to
switch between P1 and P2 manually.

5.3.4

Zero point control and adjustment

Ensure that the device is not under any pressure (if
necessary, disconnect any pressure lines).

If the device does precisely indicate zero at this
point of time, parameter

OF1

enables you to adjust

the measuring value exactly to zero. To do so, you
have to set the measuring value indicated below

OF1

to zero.

Due to the fact that the DE44 has two independent
pressure measuring systems, there is also an offset
correction parameter

OF2

for the second measuring

channel. The function and effect is identical to

OF1

After zero-point adjustment, the pressure sensing
lines can be reconnected.

5.3.5

Damping and zero-point stabilising

If there are unsteady pressure readings at this point
of time or during operation, you can use parameters

DAM

and

to stabilise the reading (and the output

signal).

The parameter

DAM

functions like a capillary throttle.

However,  it  only  acts  on  the  display,  output  signal
and  switch  points  but  not  on  the  measuring  cell  it-
self. This parameter can be used to set the reaction
time to the pressure jumps. The value range is 0.0 s
to 100.0 s.

But  with  maximum  attenuation,  it  will
take  more  than  2  minutes  for  the  read-
ing  to  also  reach  zero  after  a  pressure
jump  from  nominal  pressure  (100  %)  to
zero!

In  many  cases,  unsteady  readings  are  not  a  prob-
lem  during  normal  operating  mode,  but  this  is  not
true  for  the  idle  state,  i.e.  if  zero  (differential)  pres-
sure is expected.

In such situations, parameter

can be applied. Its

value defines a measuring value range around ze-
ro. Within this range, the measuring value is set to
zero.

Example:

A value of 0.08 mbar

is entered for

. In this

case  all  pressures  within  the  range  of  -0.08
mbar  to +0.08  mbar  are  set to  zero.  The  read-
ing  will  only  not  indicate  zero  anymore  if  the
pressure  exceeds  these  limits.  However,  the
pressure  value  and  display  do  not  correspond
to  one  hundred  percent.  The  measuring  pres-
sure and reading match again when the double
value, in this case 0.16 mbar, is reached again.

5.3.6

Setting the output signal

The  transmitter  output  signal  primarily  depends  on
the sensed pressure. However, you have the option
of  adjusting  the  output  signal  to  a  large  extent  to
suit your requirements.

However,  the  basic  measuring  range
(indicated  on  the  type  label)  and  the
type  of  output  signal  (voltage  /  current)
are not variable.

Parameters

(start of measuring range) and

(end  of measuring range)  define the two  pressures
between  which  the  output  signal  can  generally
change.  Both  values  are  adjustable  across  the  en-
tire  basic  measuring  range.  The  set  values  always
refer  to  pressure  (in  the  relevant  measuring  unit)
and  are  converted  when  the  measuring  unit  is
changed.

The assigned signal values for

and

are invari-

able (type label, e.g. 0…10 V or 4…20 mA).

If the parameter

and/or

changed, a support point table that is
active at this time will be deleted (cf.
5.3.8 or 5.3.9).

is smaller than

this is referred ´to a rising

characteristic curve. The output signal grows as the
pressure increases.

If ME is smaller than MA, this is a decreasing char-
acteristic curve and the output signal decreases
with the falling pressure.

0.08 mbar