MANUAL: 55308
REV: A
ECO: 49582
12
Figure 1.
Reference Standard Accelerometer
These high-accuracy devices, which are directly
traceable to a recognized standards laboratory, are
designed for stability, as well as configured to
accept a test accelerometer. By mounting a test
accelerometer to the reference standard and then
connecting this combination to a suitable vibration
source, it is possible to vibrate both devices and
compare the data as shown in Figure 2. (Test set-
ups may be automated and vary, depending on the
type and number of accelerometers being
calibrated.)
Figure 2.
Typical Back-to-Back Calibration System
Because the acceleration is the same on both
sensors, the ratio of their outputs (V
T
/V
R
) must also
be the ratio of their sensitivities. With the sensitivity
of the reference standard (S
R
) known, the exact
sensitivity of the test sensor (S
T
) is easily calculated
by using the following equation:
S
T
= S
R
(V
T
/V
R
)
By varying the frequency of the vibration, the sensor
may be calibrated over its entire operating
frequency range. The typical response of an
unfiltered accelerometer is shown in Figure 3.
Figure 3.
Typical Test Accelerometer Response
