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6. CALIBRATION EXAMPLE
In this example a BA538C rate totaliser is
connected to a turbine flowmeter having a K-factor
of 1050.0 pulses per litre. The flowmeter has a
magnetic pick-off with an output greater than
20mV peak at 5 litres per minute and a usable
range of 5 to 60 litres per minute.
The BA538C is required to display rate of flow in
litres per hour with a resolution of one litre and
total flow in cubic metres with a resolution of 0.01
cubic metres. Totalisation is to stop when the
flow rate falls below 300 litres per hour. The
display is to be updated twice per second and
filtering is required. In this application the
operator needs to reset the total display to zero by
simultaneously pushing the
Up
and
Down
push-
buttons. To prevent tampering the instrument
programme menu is to be protected by security
code 1209
6.1 Calibration procedure
The BA538C rate totaliser may be calibrated on-
site without disconnection from the power supply
or from the flowmeter.
Step 1
Enter the programming mode
Put the BA538C in the programming
mode by simultaneously pressing
P
and
E.
Assuming a security code has
not already been entered the
instrument will respond by displaying
'UPdAtE' which is the first function in
the main menu. See Fig 6.
Step 2
Select the interval between display
updates
With 'UPdAtE' displayed, press
P
to
reveal the existing interval between
display updates. If this is not as
required, press the
Up
or
Down
button
until ‘0.5’ is displayed. (0.5 seconds i.e.
2 display updates per second). Enter
the revised time and return to the
'UPdAtE' prompt in the main menu by
pressing
E
.
Step 3
Select the type of input
Using the
Up
or
Down
button scroll
through the main menu until ‘InPut’ is
displayed, then press
P
to reveal the
existing setting. Select ‘COIL’, the
input for a magnetic pick-off, using the
Up
or
Down
button and return to the
'InPut' prompt in the main menu by
pressing
E
.
Note:
The BA538C has two pairs of input
terminals. 3 & 4 for voltage inputs and
5 & 6 for switch contact, proximity
detector or open collector inputs.
Ensure that the magnetic pick-off,
which has a voltage output, is
connected to terminals 3 & 4.
Step 4
Position rate & total decimal points
Select ‘d.P.’ from the main menu and
press
P
. The rate and total displays
will be activated with one digit of the
total display flashing. Press the
Up
or
Down
push-button until the third least
significant digit of the total display and
following decimal point are flashing.
This gives the required total display
resolution of 0.01
Press
P
to move control to the rate
display. Using the
Up
or
Down
push-
button move the flashing digit to the
least significant position (right hand
side) which will result in no decimal
point being displayed.
Finally press
E
to return to the 'd.P’.
prompt in the main menu.
Step 5
Enter the rate scaling factor
Select ‘SCALE-r’ from the main menu
and press
P
to show the current figure.
The K factor of the flowmeter in this
example is 1050.0* pulses per litre
which should be entered as the rate
scaling factor.
Firstly to position the decimal point,
operate the
P
push-button to move the
flashing digit to the second least
significant position. Pressing the
Up
and
Down
buttons simultaneously will
then position the decimal point in front
of the least significant digit.
Using the
Up
and
Down
buttons to
adjust each digit in turn and the
P
button to transfer control between
digits, enter 1050.0 Finally return to
the 'SCALE-r' prompt in the main menu
by pressing
E
.
* May also be entered as 1050
Содержание BA538C
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