Arbiter Systems 1040C - Transducer Calibration Methods

3-11
Calibrating Transducers Using the Null Comparison Method
The null comparison method is frequently
recommended by transducer manufacturers,
since it eliminates many of the variables that
can be encountered in the course of a
conventional calibration. The basic procedure
for performing a null comparison calibration
is as follows: The inputs of a precision
standard are connected in parallel with the
inputs of the transducer under test, and the
appropriate source voltages and/or currents
are applied. A differential meter is connected
between the outputs of the precision standard
and the transducer under test, and the zero and
span settings of the transducer under test are
adjusted until the differential meter dislays
zero. The advantage of this method is that
since the input signals are exactly the same,
the accuracy of the source (and the equipment
used to measure it) are inconsequential. The
calibration accuracy is dependent only on the
individual accuracies of the precision standard
and of the differential meter.
Precision standards are usually available
from the manufacturers of the transducers,
and typically have accuracies of 0.1%. The
disadvantage of using precision standards is
that for each type of transducer to be
calibrated, a different precision standard is
required. Use of the 1040C eliminates the
need for these various precision standards,
since all of the necessary functions can be
generated from one unit. Also, since the
1040C is a precision source and no external
meters are necessary, the simplicity of the
calibration procedure is about the same as that
of the null comparison method.