Table of Contents
Advertisement
3.2.3. Calibration for Vibration Measurements
28
Using the Type 4291 Accelerometer Calibrator
The preferred method of calibration consists of calibrating the whole measuring chain by
applying a known vibration level to the accelerometer and adjusting the gain of either
the accelerometer preamplifier used or the 2010 analyzer section to obtain a meter def-
lection equal to that level. The Type 4291 Accelerometer Calibrator provides a sinu-
soidal vibration level of 1 0 ms
-2
peak (at 79,6 Hz) and since the 2010 rectifier is a
true RMS type the calibration should be for the RMS level of 7,1 ms
-2.
The meter will
then display RMS vjbration levels.
If the analyzer is used for measurement of sinusoidal vibration signals only - as will be
the case when the FREQUENCY RESPONSE control is set to "Selective" for the actual
measurements - then the 201 0 may be used to measure peak vibration levels. In this
case the calibration deflection should be 1 0,0 rather than 7,1.
Four vibration measurement meter scales are available for use with the 2010, corre-
sponding to different ranges of sensitivity of the accelerometer and preamplifier used.
They are listed in Table 3.2. Since most preamplifiers used will provide a choice of sensi-
tivities, however, it is possible to use any of these scales in most applications.
Combined sensitivity
of accelerometer and
Preferred Scale
preamplifier
1,7 to 6,0 mV per unit
SA 0142
6 to 17 mV per unit
SA 0058
17 to 60 mV per unit
SA 0143
60 to 170 mV per unit
SA 0144
780185
Table 3. 2. Vibration Measurement Scales for use with 2010
The scales are annotated for vibration measurement in g's, but they may be used just as
easily for measurement in ms -
2
simply by reading "ms
-2"
for "g" both during calibra-
tion and during measurement.
To perform the calibration, proceed as follows:
1.
Secure the accelerometer to the Calibrator and adjust the Calibrator as described in
its Instruction Manual.
2.
Set the controls on the 201 0 as follows:
GAIN CONTROL
OUTPUT SECTION ATIENUATOR
EFFECTIVE AVERAGING TIME
READ OUT SELECTOR
FREQUENCY RESPONSE
INPUT
CALIBRATION
"Cal."
"x
1 "
"Fast"
"Lin.", "AC" or "DC"
"Linear"
As appropriate
"Cal. Off"
3
.
Set the INPUT SECTION ATIENUATOR so that the illuminated full scale deflection in-
dicator at the bottom of the meter scale is appropriate for the units to be used.
Advertisement
Table of Contents
