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These
models may be used with any series-opposed 5-, 6-, or 7-wire LVDT
sensors or 3-wire variable reluctance transducers that can be
operated with a 3-kHz frequency. Optional remote sensing is
available for long cables.
The
Model 3130 LVDT Conditioner is the basic "Form
1" instrument.
The
Model 3230 LVDT Conditioner / Indicator is the basic "Form
2" instrument, providing vivid front-panel digital
indication of measured values. The available scales allow
ready calibration over virtually any measurement range, with a
wide choice of engineering units. Instrument sensitivity and
resolution allow precision to a fraction of a microinch, if
required.
The
Model 3330 LVDT Conditioner / Indicator / Controller is the basic "Form 3"
instrument, and includes HI/LO limit detection. This feature
is useful in a wide variety of "GO NO-GO" gaging
applications (see Using a 3000
"Form 3" Conditioner / Indicator / Controller for "GO
NO-GO" Dimensional Gaging of Parts). |
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Working
on the synchronous carrier-demodulator principle, all three instruments
supply amplitude-regulated 3-kHz AC excitation to the transducer.
Two standard 5-V outputs are produced (see Specifications).
Each output is precisely proportional to LVDT core displacement over the
full ± range of the sensor. Sensitivity is widely adjustable,
allowing full-scale output for input displacements as small as ±0.001
inch (±0.0254 mm).
A
unique phase-control circuit automatically and continuously adapts the
instrument to any signal phase shift occurring in the transducer or
cable. This simplifies setup procedures, and ensures optimum
sensitivity and linearity for each type of LVDT sensor employed.
Span
adjustment is accomplished through 12-turn Coarse and Fine front-panel
controls plus 5 internal range multiplier switches. Nominal maximum
sensitivity is 10 mV (in-phase component) for full-scale input.
For
typical 3130/3230/3330 operations, see the following
applications:
3000
Series options applying to these instruments include
AC
LVDT Instrument Specifications [Top 
]
(Click
here for 3000 Series General Specifications)
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Input
Type |
Series-opposed
5-, 6-, or 7-wire LVDT sensor or 3-wire variable reluctance transducer
capable of 3-kHz operation and having primary impedance greater than 80
Ω |
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Input
Range (full-scale) |
±0.001
to ±4.000 inches (±0.0254 to ±101.6 mm) |
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Excitation
Supplied |
3
kHz, amplitude regulated |
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Analog
Outputs |
Two
outputs, each ±5 VDC full-scale with 50% overrange, 5 mA maximum;
low-pass corner frequencies of 2 Hz and 400 Hz, respectively |
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Analog
Filtering |
Active
low-pass filters provide -60 dB per decade above cutoff frequency
("f"); full-scale slew time is 1.4/f sec |
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Output
Ripple and Noise |
0.15%
of full scale (rms) maximum for 400-Hz output; 0.02% for 2-Hz output |
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Accuracy
(typical, following calibration) |
Varies
from 0.1% to 1.0% of calibrated range* |
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Display
Resolution (Models 3230 and 3330) |
0.02%
of full scale |
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*
Depending on the linearity characteristics of the LVDT element itself.
The resolution and accuracy of these instruments are considerably in
excess of what is generally useful in practical applications. In
high-sensitivity LVDT measurement, the ultimate limits of accuracy are not
imposed by the instrumentation, but by considerations of dimensional
stability that pertain to the transducer, the fixture, and/or the measured
object itself. In general, accuracy to 0.0001 inch or better can be
achieved only with carefully designed fixtures and under conditions of
precise temperature control. |
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