BEKA BA304C, Manual, Page: 8 / 15

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6.2 Span adjustment
Span is defined as the difference between the
number displayed with 4.000mA input, and the
number displayed with 20.000mA input. It is
adjustable between 0 and 1999 in four ranges. Fig
6 shows the position of the span links and the span
potentiometer.
Span links
Difference in display
Position with 4 & 20mA input
adjustable between
000 to 500 000 and 500
or 500 to 1000 500 and 1000
or 1000 to 1500 1000 and 1500
or 1500 to 1999 1500 and 1999
6.3 Decimal point
A decimal point may be displayed between any of
the four digits. The position or absence of this
dummy decimal point is determined by the position
of the decimal point link shown in Fig 6. When
calculating the required span and zero settings the
decimal point should be ignored.
6.4 Reverse action
Normally the BA304C display increases as the
input current increases, but this can be reversed.
Please contact BEKA associates for details.
6.5 Calibration example
The BA304C is required to display:
25.0 with 4.000mA input
115.0 with 20.000mA input
i.e. A zero of positive 250 (Ignoring decimal point)
A span of 900 (Ignoring decimal point)
A decimal point in position 00.0
The following adjustments are required:
Step 1 The BA304C is required to display a
positive zero therefore the suppression
/ elevation links should be put in the
elevation position.
Step 2 The required zero is 250, therefore the
zero link should be put in the 0 to 500
position.
Step 3 The required span is 900, therefore the
span links should be placed in the 500
to 1000 position.
Step 4 The decimal point is required in front of
the least significant digit, therefore the
decimal point link should be placed in
the 00.0 position.
Step 5 With 4.000mA input adjust the zero
potentiometer until the indicator
displays 25.0
Step 6 With 20.000mA input adjust the span
potentiometer until the indicator
displays 115.0
Step 7 Repeat steps 5 and 6 until both
calibration points are correct. The span
and zero controls are almost
independent so it should only be
necessary to repeat each adjustment
twice.
6.6 Over and under-range
If the indicator display range is exceeded, the three
least significant digits will be blanked. Under-range
is indicated by -1 and over-range by 1. If the
display range is not exceeded, the BA304C will
produce accurate readings outside the 4/20mA
current range. Although not guaranteed, most
BA304C indicators will operate between 3 and
25mA.