Ectron 451, Instruction Manual

Page: 38 / 74

To have the output voltage correspond to engineering
units or if exact values of voltage versus displacement
are required, then measurements of displacement values
will have to be made. If this is done with high accuracy
then precise displacement-versus-voltage results can be
obtained. These results can have a much higher accuracy
than with a procedure of calibrating the LVDT with the
conditioner in the cal lab, mounting the device to ap-
paratus under test and then taking the data. For instance,
the example mode allows the displacement measure-
ments to be made on the apparatus under test rather
than on the LVDT. This can eliminate the errors of the
mechanical connection between the apparatus and the
transducer.
Conventional applications of LVDTs usually depended
on calibrating the transducer with the conditioner in a
cal lab, mounting the device where it will be used, and
then running the test. If conditions change between cali-
bration and the test, (temperature changes, excitation
voltage or frequency change, the transducer is dropped)
the calibration values will no longer be valid.
Scale Mode Choose scale mode if the transducer sensitivity is ac-
curately known and the numerical values of output volt-
age and the corresponding values of transducer
displacement (in mil’s, mm’s, or deg’s) are known.
For example, if a one-inch LVDT is being used, and
an output of from
−
5 V to +5 V is required for the
transducer going from
−
500 to
+
500 mils, just enter
these values, and the conditioner is set up. So, first set
the units to inches and the transducer sensitivity to its
predetermined value. In scale mode, set Point 1 V to
−
5 V, Point 2 V to
+
5 V, Point 1 displacement to
−
500 mils and Point 2 displacement to
+5
00 mils. This
procedure will set up the conditioner to the transducer.
If the polarity is backwards, reverse the signal leads to
the Model 451.)
DETERMINING THE ACTIVE MODE
To determine which operating mode is active, press the display. If zero control is off, the
first screen to appear is the active mode. If zero control is on, the first screen to appear is
the autozero screen. (Zero control will be on if an autozero has been set or if zero control
has been actively turned on.)
If zero is on, to determine the active mode, press the display and rotate the knob until you
reach
GAIN MODE SETUP . Pressing the display will show the GAIN ADJUST display
if the gain mode is active. If the gain mode is not active, the screen GAIN ACTIVE ? NO
will be displayed.
Applications Model 451
4-4