Electronics System Design Practical II
EXPERIMENT NO II
Design of SPAN ZERO circuit.
Zero and span adjustment are
necessary for transducer and instruments. It may be necessary to change the
original output signal in certain industrial
applications.
By adjusting both zero and span, we
may set the instrument for any range of measurement within the manufacturers
limits. Adjusting one has an effect on the other. Specially changes made to the
span adjustment almost always alter the instruments zero point.An instrument
with interactive zero and span adjustments requires much more effort to
accurately calibrate, as one must switch back and forth between the lower and
upper range points repeatedly to adjust for accuracy.
Example: Consider the case of 4mA to 20mA output of a pressure
transmitter and its maximum when input signal of the same parameter is maximum.
In this case, minimum current output is set to 4mA and maximum current output
is set 20mA. This adjusts the span of the instrument.
Implementation with differential Amplifier LM 741 typical circuit is as follows:
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