97029 Rev C.1 09/18
Page 10 of 15
5.2.3 Frequency selection
The user has a choice of three frequencies. Momentarily press the
FREQ
button to select the
desired frequency as indicated on the respective LED. During frequency changes, the output of the
shaker is turned off momentarily. It is normal for the
OOR
indicator to illuminate briefly after a new
frequency is selected. See table 1 for additional information.
The ReferenceMate 2500 will always produce an amplitude of 1 g at the selected frequency.
61.4 Hz is the most common frequency selected for machinery vibration and analysis when
working with imperial units (US). One g at 61.4 Hz is equal to 1 in/sec (ips) velocity.
100 Hz is the preferred frequency for checking accelerometer performance against calibration
data. 100 Hz is the most common reference frequency used by accelerometer manufacturers,
thus allowing for a comparison with the original calibration certificate.
159.2 Hz is the most common frequency used when working in metric units where 1 g is equal
to 9.81 m/sec
2
acceleration, 9.81 mm/sec velocity and 9.8
µ
m displacement.
5.2.4 RMS/PEAK
Select between
RMS
and
PEAK
by holding down the
FREQ
button. Figure 3 below illustrates the
relationship between
PEAK
and
RMS
.
Figure 3: the relationship between peak, RMS, and peak-to-peak
RMS value = 0.707 x peak value
Peak value = 1.414 x RMS value
Peak to peak value = 2 x peak value
Peak to peak value = 2.828 x RMS value
