5.15 Total scale factor: ‘5CALE-t’
Together with the timebase 't-bA5E', this is a
dividing factor that defines the arithmetic
relationship between the rate and total displays.
When the flow rate and the total flow are required
in the same units 5CALE-t = 1.0
The total scale factor may be set to any value
between 0.0001 and 99999 allowing the total flow
and rate of flow to be displayed in different
engineering units.
5CALE-t = Units of rate display
Units of total display
When calculating 5CALE-t the required units of
measurement for the total display must be
converted to those used for the rate display as
shown in the following example:
The BA558E rate display represents litres per
second but the total flow display is required in UK
gallons. There are 4.5461 litres in a UK gallon.
5CALE-t = Units of rate display
Units of total display
= 1 litre
1 gallon
= 1 litre
1 / 4.5461 litres
5CALE-t = 4.5461
Alternatively, if the total display is required in
thousand of UK gallons
= 1 litre
1 / 4546.1 litres
5CALE-t = 4546.1
The total scale factor 5CALE-t is not dependent on
the rate display units of time. i.e. flow units per
second, minute or per hour. The timebase t-bA5E
accounts for these differences.
To check or change the total scale factor select
'5CALE-t' from the configuration menu and press
P
to reveal the existing setting, one digit will be
flashing. The value of the flashing digit may be
changed by pressing the
▼
or
▲
button. When
this digit is set as required pressing
P
will transfer
control to the next digit, which may be adjusted in
the same way.
To position the decimal point, repeatedly operate
the
P
button until the decimal point starts flashing.
The decimal point can then be positioned by
pressing the
▼
or
▲
button.
When the required total scale factor has been set,
press
E
t
o enter the number and return to the
‘5CALE-t’ prompt in the configuration menu.
5.16 Clip-off: ‘CLiP-oFF’
To prevent totalisation of very low flow rates, which
over long periods may result in significant
totalisation errors, the BA558E rate display can be
conditioned to stop totalisation when the flow rate
falls below a specified clip-off threshold. Clip-off
is an absolute value, for bi-direction flow systems it
inhibits totalisation for flow rates bclip-off
and –clip-off.
Clip-off is shown in the same units as the
instruments rate display. To check or change the
clip-off threshold select 'CLiP-oFF' from the
configuration menu and press
P
to reveal the
current level, one digit will be flashing. The value
of the flashing digit may be changed by pressing
the
▼
or
▲
button. When this digit is set as
required pressing
P
will transfer control to the next
digit, which may be adjusted in the same way.
When set as required, press the
E
button to enter
the revised threshold and return to the ‘CliP-oFF’
prompt in the configuration menu.
For uni-directional flow when the flow rate falls
below the clip-off threshold, totalisation is inhibited,
the hold annunciator is activated but the flow
indicator continues to rotate until the input current
falls below 4mA.
For bi-directional flow when the positive or
negative flow rate is less than the absolute clip-off
threshold, totalisation is inhibited and the hold
annunciator is activated. The flow indicator
continues to rotate until the low rate is less than
±0.05% of flow rate display span.
5.17 Local reset of total and grand total.
‘LoC. R5Et’
This function contains two sub-functions ‘t-rE5Et’
and ‘Gt-rE5Et’ which allow the total display and the
grand total to be independently reset using the
instrument push buttons without access to the
configuration menu from the operating mode.
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