All strain
gauged transducers (load cells, extensometers, etc.) are normally
a full wheatstone bridge design. They are excited or powered
by a voltage, typically 5 or 10 VDC. The output is proportional
to the excitation. For this reason the calibrated output is
often expressed as 2.345 mV/V, for example. This means the
output at full scale will be 23.450 millivolts if the excitation
is exactly 10 volts. This data is provided by Epsilon on the
calibration certificate.
All strain gauged sensors must be connected to some external
electronics to provide readings. This electronics provides
the excitation and normally amplifies the output to a high
level DC voltage. This resultant voltage is used for readout
or control of the test machine. In newer digital systems the
voltage output is converted via data acquisition hardware
into engineering units of strain. In instances where a chart
recorder or X-Y recorder is used, the output is set to easily
yield a specified strain/cm on the graph.
When any new device like an extensometer is first used, the
electronics must be set up with the unit to read correctly.
There are several ways to accomplish this. Generally the process
is very straightforward. If your extensometer will be connected
to an available channel for an extensometer in your test controller,
we normally supply the unit with the correct connector to
plug right in. For data acquisition systems, the required
strain gauged signal conditioning is required. Often this
is part of the system. For boards that require high level
inputs or for use with recorders, Epsilon offers the electronics
you need.
Detailed calibration procedures are provided by Epsilon to
cover virtually all approaches to calibration.
|
Calibrating
Extensometers with Electronics
|
| Required
for any extensometer you buy, this step can be done
many ways, most of which are quite simple. The most
common options are: |
Using
Epsilon’s Shunt Calibration Module
| As
detailed in shunt calibration section, this is a very
quick and easy way to set your electronics, regardless
of brand. The two points needed for the calibration
are provided. |
With
Electronics from Epsilon
| All
extensometers purchased with electronics from Epsilon
are shipped as fully calibrated systems. The output
and/or display are factory set to exact values. No further
calibration is required. Periodic re-calibration can
be done by Epsilon. |
|
With
an extensometer calibrator from Epsilon
|
| Epsilon’s
model 3590 Digital Electronic Calibrator is the easiest
to use unit available. This is an ideal way to perform
calibrations if you have many extensometers and wish
to calibrate your own. They allow you to check many
data points along the curve, for the highest accuracy.
|
|
By
calibration services such
as the equipment manufacturer.
|
| Epsilon’s
extensometers can be calibrated with test controls by
any calibration service with the capability of calibrating
extensometers. Many customers have their entire test
machine re-calibrated annually by the service department
of the manufacturer. This includes the load cell, extensometers
and any other sensors. Any competent service will have
no difficulty with Epsilon’s extensometers. |
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