Ono Sokki DS-2000 Series User manual

ONO SOKKI CO., LTD.
DS-2000 Series
Vibration Measurement

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Contents
1. Flow Chart to Measurement
2. Device Connections
3. FFTAnalyzer Setup
4. Starting Measurement
5. Data Processing
1. Flow Chart to Measurement
* The following explains procedures for measuring vibration using an "accelerometer."
Accelerometer
connection
Input source setup
Engineering unit setup
Voltage range setup
Frequency range setup
Frequency differential/integral
Data processing (averaging)
Saving data
Copy data
Connect an accelerometer to the DS-2000.
Set the type and output sensitivity
of the connected sensor.
Set the voltage sensitivity, frequency range,
Y-axis scale, and frequency differential/integral.
Process data (averaging) and then save it.
Then, copy data and then paste it to other
applications.

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2. Device Connections
2-1 Device Connections
Connect the DS main unit and the PC as follows.
Personal computer (laptop)
DS-2000 rear panel
ONOLINK II
→PCMCIA
Key protector
(USB or parallel)
100VAC 100VAC

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2-2 Connection with Sensor
Connect an "accelerometer" to the FFT analyzer. The accelerometer comes in two types:
built-in amplifier type and charge output type. Basically, connect each sensor with the DS-
2000 as follows:
The NP-3000 series accelerometer can be directly input through a BNC conversion
adapter.
Signal input section
NP-0021 BNC conversion adapter
NP-3000 Series
Accelerometer
CH-1100
Charge amplifier
NP-2000 Series
Accelerometer
Install the accelerometer perpendicularly to the vibration direction by closely contacting the
bottom of the accelerometer and the measurement surface. Fixation by screw provides the
highest frequency sensitivity. When using a magnet base, the use of silicon grease increases
adhesion.

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3. FFT Analyzer Setup
3-1 Input Source Setup
Set the sensitivity, operating conditions, etc. of the sensor connected to the FFT analyzer. The
following shows a case where a piezoelectric accelerometer based on the following sensitivity
is used.
①
②
Double-click the icon of DS-0221FFT to start the application. If a personal computer is
connected with the measurement unit, the relay contact generates sound.

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Select the Input menu and then select Voltage Range Set.
Click [▼] on the right of the
Input Source box and select
SENSOR (2.0mA). (Refer to (2)
in the sensitivity table.)
Click OK to apply the settings.
3-2 Engineering Unit Setup
Set the sensitivity of the sensor in order to directly read amplitude values using
engineering unit.
Select Unit / Calibration from the Input menu.
Enter engineering unit
of acceleration (m/s2). Enter 0.00975 because of 9.75mV/m/s2. (Refer to (1) in the sensitivity table.) Click [▼] on the right of
the box and select V/EU.
Check this box.
* Numerical values and characters can be input from the keyboard. Further, clicking [...] on the
right of the text box displays a pad for numerical and text input.

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4. Starting Measurement
4-1 Voltage Range and Frequency Range Setup
First, observe the vibration waveform.
Since the screen displays power spectrums of CH1 and CH2 with the initial setup, select
time-axis display of a channel subjected to signal input.
Click the comment area to activate
it. Select Disp. Data Select from the
Display menu.
Select a function
to be displayed.
Select an input
channel.
* Double-click the comment area to display the Disp. Data Select dialog.
Display the power spectrum of the input channel in the same manner.

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Set the voltage sensitivity while monitoring the magnitude of the input signal. Make setting so
that the waveform fits into the time-axis display screen.
Click the Input menu and select Voltage Range (in the same manner as 3-1, "Input Source
Setup) or select a button in the tool bar.
The sensitivity can also be set by selecting
Voltage Range from the Input menu. Adjust the sensitivity so that
the waveform is not exceeded.
If the waveform is
exceeded, an
indicator lights up in
red. (Normally green)
Set an input channel
and voltage sensitivity
in the tool bar.
Set a frequency range. Narrow down the range while monitoring the power spectrum.
Select Frequency
Range from the Input
menu and then set a
range.
The range can also be
set from the tool bar.
* With the initial setup, the signal is sampled at 2048 points resulting in a frequency resolution
of 1/800. Therefore, the narrower the frequency range, the higher becomes the frequency
resolution.

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4-2 Cursor Function
Read the frequency and the amplitude of power spectrum using the cursor function. With the
initial setup, the peak search function is selected and therefore the maximum amplitude is
automatically searched for. Further, change the Y-axis scale as required.
Select Search.
Select Cursor Set from the
Display menu. To change the
Y-axis scale, select Y-Axis Set.
Select an option button.
• Default (initial setup)
• Auto (automatic setup)
• Manual (manual scale)
To make the same scale
setting for all screens, check
this box.
For Manual, set
Upper and Lower
limit values.
Select Lin or Log
(logarithmic) scale.
For vibration
measurement,
select Lin.

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Amplitude
Cursor values are
displayed at the
bottom of display
screen.
Can be set also from the tool bar.
* Menu can be easily opened by right-clicking on the screen.
4-3 Frequency Differential/Integral
At the time of vibration measurement, the vibration quantity is handled as acceleration, velocity,
and displacement depending on the frequency to be measured. Relation between units is shown
below.
Acceleration ∝ af
2
Acceleration
Integral Differential
Velocity ∝af
Displacement ∝a
Velocity
Integral Differential
Displacement
region
Frequency
f
Velocity region Acceleration region
Displacement
* Generally, the amplitude of the displacement, velocity, and acceleration increases at 10Hz or
below, at 10Hz to 1kHz, and at 1kHz or above, respectively.

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Perform frequency integral. Activate the spectrum screen, click the Analysis menu, and select
Frequency jw.
Displacement →
Velocity
Displacement →
Acceleration
Acceleration →
Velocity
Acceleration →
Displacement
Select an
engineering unit.
Perform single integral to convert acceleration to velocity.

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5. Processing and Saving Data
5-1 Averaging
Averaging is performed in order to improve data accuracy. Here, summation averaging of a
general power spectrum is performed. At the time of averaging, it is necessary to perform
overlap processing according to the frequency range. Overlap of data occurs if the signal capture
time is longer than the FFT operation time. The lower the frequency range, the longer becomes
the capture time and the more remarkable becomes overlap. With the DS-2000, overlap occurs
except in the MAX range (40kHz) in the case of a 4-Ch system.
* In the above waveform,
( ) Sampling time that is necessary for the FFT analysis
( ) Time for a single FFT calculation
Therefore, the overlap amount is after deducting the FFT calculation time from the FFT capture time.
The same data is arithmetically averaged while overlapping.
Time to import a frame of waveform
Time to import a frame of waveform
Amount of overlapped waveform
FFT calculation time
Time to import a frame of waveform
Amount of overlapped waveform
FFT calculation time

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Select Sampling from the Input menu.
The amount of
overlap can be set
in 25% steps or
user-defined.
* When the amount of overlap is set to 0%, new data is averaged. However, if the frequency
range is very low, processing takes long time. In this case, the number of averaging can be
increased or average time can be set. Select Average from the Input menu.
Select the number of
averagings or averaging
time.

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Perform averaging
using tool buttons.
Performs summation averaging 10 times after overlap
processing.
5-2 Saving Data
Save measurement results. All data currently displayed on the screen can be saved
simultaneously, or only specified data can be saved. Procedures for saving specified data are
shown below.
Select Save Data (Select) from the Input menu.
Specify a location for saving data.
Specify data format
(binary or text).
Press the
Save button
to execute.
Select the Add button
to select specified
data.
The specified data are listed.
* .dat denotes the binary format and .txt the text format.
Specify the number to
be set to the data.

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* When you click the Add
button, the dialog shown at
right appears. Select specified data.
Set a file name.
Specify a channel in
relation to data to be
saved.
5-3 Copy Function
Click OK to apply the settings.
Measurement data can be temporarily put in the clipboard. The data in the clipboard can be
easily pasted to other applications without saving.
Select Copy Setup from the Edit menu.
Select Bitmap or
Text using the
option buttons.
Click OK to apply
the settings.
After determining the data format with Copy Setup, select Copy from the Edit menu.

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CAUTION:
1. The copyright of this procedure manual is reserved by Ono Sokki Co., Ltd.
2. Duplication without prior permission is prohibited.
3. This procedure manual explains general measurement procedures. Ono Sokki assumes no
responsibility for data obtained through a specific operation performed by the customer.