Addendum to User’s Manual
EDI-53 Series Digital Indicator
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Addendum
Model EDI-53P-C Digital Indicator for Potentiometric Sensors
1
INTRODUCTION
The EDI-53P-C is a modified version of Encardio-rite’s EDI-53P potentiomeric indicator. The standard
EDI-53P indicator is meant for use with Encardio-rite’s EDE-PXX series potentiometric displacement
transducers that need 5Vdc excitation and output 0-2V dc signal.
The
EDI-53P-C
is a customised version that is intended for use with passive potentiometric sensors,
like Glotzl series GWL./.. potentiometric displacement transducers.
Except for the differences described below, the EDI-53 Series Digital Indicator User’s Manual [ER
document No. WI-6002.67 Rev. 0] is valid for all other operations and technical specifications of this
indicator. The section numbers given below refer to the original section numbers of the User’s
Manual.
2
TRANSDUCERS
The EDI-53P-C is designed for measurement of wiper position of passive potentiometric sensors
relative to the reference terminal.
An example of such sensors is passive potentiometric displacement transducers from some
manufacturers, e.g series GWL ./.. potentiometric displacement transducers from Glotzl.
2.1
Measurement of transducer output
The indicator applies a nominally 2V dc excitation across the potentiometer terminals and measures
the output voltage between the reference terminal and the wiper of the potentiometer. The ratio of the
two voltages is the ratio of the total potentiometer resistance and the resistance between the
reference terminal and the wiper of the potentiometer. The indicator displays the ratio of the two
resistances on a scale of 1.000 in the basic voltage measurement mode.
In other words, the when the wiper is at 0% of its travel the display will show 0.0000 volts, at 50%
travel it will show 0.5000 Volts and at 100% position it will show 1.0000 Volts.
2.2
Calculation of parameter value in engineering units
The EDI-53P-C uses the following equation to calculate the potentiometric output directly in terms of
proper engineering units.
Y = G
×
(P
÷
100)
[Eqn. 3.3.4]
where, Y is the measured parameter in appropriate engineering units, G is gage factor to be
calculated from the sensor manufacturer’s data sheet, and P is the potentiometer wiper position
expressed in % of full scale.
The gauge factor, ‘G’ is calculated in the following way. Let’s say, for a displacement transducer with
a measuring range of 50 mm the calibration certificate mentions that 50 mm corresponds to 99.85 %
of full scale (or gives an output of 0.9985 volts with 1 V excitation across potentiometer) the gauge
factor would be given by
G = (50
÷
0.9985)
The value of ‘G’ for each individual transducer has to be entered in setup for displaying the measured
value in engineering units.
