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7. CALIBRATION EXAMPLE
In this example a BA338C 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 BA338C 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
7.1 Calibration procedure
The BA338C 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 BA338C 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 9.
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 BA338C 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 that
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 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.
