SM0486
(1) The diagram in Figure 4 indicates that the signal from the pickup goes
to the amplifier section.
This section consists of two parts: the first with
adjustable gain; the second with fixed gain.
For velocity measurements, the two
sections are connected in series by a linear attenuator network. For displacement
measurements, this linear network, is replaced by an integrator.
During
"calibrate signal" voltage to the proper value.
This voltage is then applied to
the input of the instrument. When this is done, the gain may be adjusted to permit
direct reading of velocity or displacement from the meter.
In a practical
application, you must fasten the pickup securely to the machine or structure under
study. You must locate the point of vibration and fasten the pickup at that point.
(2) In some instances the pickup is attached to a lightweight, rigid probe
and held manually against the vibration checkpoint.
The average velocity may be
read directly from the meter.
The frequency of vibration may be calculated from
the reading of displacement and velocity by the use of the following equation.
With f representing the frequency of vibration (cycles per second), Vaverage as the
average velocity of vibration (inches per second), and D as the peak-to-peak
displacement in inches, the equation reads:
(3) When you operate the equipment to
measure
vibration,
certain
preliminary control settings are made as follows:
Turn the calibrate signal and sensitivity controls to full counterclockwise
positions.
Turn the range control to its OFF position.
Leave the input network and channel selectors in any position.
Connect the meter powerline cord to 115 volts AC.
Turn the power switch to
its ON position.
(4) After you complete the preliminary control settings, you must complete
a series of meter circuit checks.
You perform the zero test by indexing the
operation selector through the V x 1.0, D x 1.0, and D x 0.1 positions. A reading
of not more than 2 percent of full scale should be obtained, indicating a noise
level of less than 2 percent.
You continue the meter circuit tests with the
calibrate signal test.
Turn the operation selector to C and then depress the
calibrate signal knob for a one-third to full-scale deflection of the pointer. Set
the meter indicator at 5 on the lower scale and release the calibrate signal knob,
preparatory to the sensitivity control test.
(5) When you perform the sensitivity control test, index the channel
selector to each of its four positions. At each position, the output meter reads
full scale when the applicable channel sensitivity control is
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