97029 Rev C.1 09/18
Page 14 of 15
7.2
Recommended instrumentation setup
A digital multimeter (DMM) can be used to measure the signal
amplitude. The DMM should be a high quality unit that has a current
calibration certificate to ensure measurement accuracy. Figure 6
shows the attachment of a probe and clip lead going to a DMM.
An o
scilloscope will provide information as to the shaker’s wave
shape. The test point output should be a sine wave with low
distortion (less than 7%), as shown in Figure 7A. Excessive
distortion or high levels of noise (Figure 7B) indicates possible
mechanical damage to the shaker mechanism. If high levels of distortion, an incorrect output level,
or out-of-tolerance frequency is observed, the REF2500 should be returned to the factory for
service. There are no user-serviceable parts in the unit.
The table below shows the expected test point output voltage amplitudes. The amplitude depends
on the peak/RMS setting, as shown. Measured values should be within ±3.0% of those specified.
Figure 7A: Acceptable sine wave from reference mate.
Figure 7B: An example of unacceptable noise
Table 4: Test point output voltages
Setting
RMS value
Peak value
Peak to Peak value
RMS
100 mV
141 mV
282 mV
Peak
70.7 mV
100 mV
200 mV
A frequency counter may also be used to confirm the frequency of the excitation signal. The
frequency should be within ±1.5% of the selected frequency.
Figure 6: Probe connected
to the test point pins
