31
2.5.9 Rate scale factor: ‘SCALE-r’
‘SCALE-r’ is a dividing factor which may be
adjusted between 0.001 and 99999999.
Together with the instrument timebase, ‘SCALE-r’
defines the arithmetic relationship between the
pulse input frequency and the rate display.
e.g. If the BA364D is required to display a rate of
1 unit per hour when 3 pulses are received per
second:
SCALE-r = (Number of input pulses/s) x (Timebase)
Required display / unit of time
where timebase equals
1
for rate display / second
60
for rate display / minute
3600
for rate display / hour
SCALE-r = (3 pulses / s) x (3600)
1 per hour
SCALE-r = 10800
To check or change the rate scaling factor select
'SCALE-r' from the main menu and press
P
to
reveal the existing setting, one digit will be
flashing. The value of the flashing digit can be
changed by pressing the
Up
or
Down
button.
When this digit is correct pressing
P
will transfer
control to the next digit.
To position the decimal point in the rate scale
factor, move the flashing digit to the left hand
side of the required decimal point position and
simultaneously press the
Up
and
Down
buttons.
When the required rate scale factor has been
entered, press
E t
o store the number and return
to the main menu.
2.5.10 Rate display filter: ‘FILtEr’
This digital filter has two independent adjustable
parameters enabling the rate display frequency
response to be tailored for optimum performance.
The filter parameters are controlled by a two digit
number. The first digit defines the amount of
filtering applied to the display as shown below.
First digit
Filter time constant
seconds
0X
0
1X
1.3
2X
4.3
3X
6.5
4X
8.7
5X
11.3
6X
15.7
7X
20.9
8X
25.2
9X
31.5
The second digit defines the deviation from the
displayed rate at which the filter will be
overridden and the rate display will move rapidly
to the new value.
Second
digit
Magnitude of step
change which will
produce a rapid
response
X0
Off
X1
1%
X2
2%
X3
4%
X4
8%
X5
12%
X6
16%
X7
24%
X8
32%
X9
64%
By careful adjustment of the two parameters a
stable display with an acceptable step input
response can be obtained for most applications.
During commissioning it is recommend that
initially the second digit is set to 0 (off) and the
first digit is adjusted to provide acceptable rate
display stability. The second digit should then be
increased until the selected step size is greater
than the noise on the display signal, at which
setting the rate display will again become stable.
These will be the optimum filter parameters for
acceptable rate display stability and a fast
response to a large rate signal change.
To check or change the filter select 'FILtEr' from
the main menu and press
P
to reveal the current
settings. Pressing the
Up
or
Down
button will
change the flashing digit and
P
will transfer
control to the second digit. While making
adjustments the filtered rate display is shown on
the lower display so that stability can be
assessed. When set as required, press the
E
button to enter the revised parameters and return
to the main menu.
2.5.11 Timebase: ‘t-bASE’
This function multiplies the rate display by 1, 60
or 3,600 to show rate per second, per minute or
per hour.
To check or change the timebase, select 't-bASE'
from the main menu and press
P
which will
reveal the current setting. Pressing the
Up
or
Down
buttons will scroll through the three
options:
Display
Units
tb-1
for rate / second
tb-60
for rate / minute
tb-3600
for rate / hour
When the required timebase is displayed press
E
to enter the selection and return to the main
menu.
