Acceleration Pickup Frequently Asked Questions

Please check for looseness and tighten securely. Tighten until there is no play in the cable-side connector.

(Note)
If a locking washer is included, there may be play in the connector even if it becomes tight. The washer may also become excessively crushed, but it is necessary to tighten it until there is no play.

I will check by replacing it with a spare cable. Depending on the model, it can be verified using the disconnection detection feature utilizing CCLD functionality.

Check that CCLD is turned on in the settings of the sensor amplifier and FFT analyzer. Additionally, it is necessary to select the current value that matches the sensor specifications.

(Note)
Always set the input coupling to AC. When the CF-7200 analyzer removes the detector, the CCLD will automatically turn OFF, so please make sure to turn the CCLD back ON when reconnecting.

When using the NP-0021 miniature/BNC conversion adapter, caution is required. Depending on the acceleration pickup, the thickness of the rubber packing included with the NP-0021 may prevent it from being inserted properly, leading to poor contact. In such cases, please remove the rubber packing before use. This is especially important when connecting to the acceleration pickup NP-3211; be sure to remove it.

Details "It seems that the signal from the acceleration pickup occasionally cuts out, and there may be disconnection detection or no signal output"

Secure the cable firmly in a way that prevents excessive force from being applied to it.

Especially when using charge output type accelerometers, the cable itself can easily generate electrostatic noise if it vibrates, so it should be securely fixed to prevent vibration.

Rapid temperature changes can cause distortion in the sensor case due to thermal expansion, leading to low-frequency noise (pyro effect). Care should be taken to avoid direct exposure to wind and to prevent radiant heat from sources such as incandescent bulbs.

• Ensure that the ground connections for the measurement target, sensors, sensor amplifiers, and FFT analyzers are secure. (When the grounding is solid, this method is the most resistant to noise. Even if each device is connected to the factory ground terminal, if the main factory ground is weak, ground loop noise may occur.)
• Disconnect one ground of the measurement system or sensor amplifier/FFT analyzer. (If the ground is not secure, a ground loop may form, and in that case, to break the ground loop, use a float (insulated) type sensor or insulated studs (custom-made upon request. Contact your nearest sales office for consultation.) to disconnect the ground of the measurement system, or cut the loop by not grounding the sensor amplifier/FFT analyzer.)

(Note)
In this case, the sensor amplifier and FFT analyzer need to have a reliable ground connection. Additionally, insulated studs are available on a custom basis. Contact your nearest sales office for consultation.

• Try changing the installation position of the sensor.
• Try to gain distance with insulating studs, etc. (Insulating studs are available on a custom order basis. Please consult with your nearest sales office.)
• The amplifier built-in type is easily affected, so let's try switching to a charge output type sensor.

• Charge output types transmit signals with high impedance, making them susceptible to picking up noise during transmission. Let's try switching to a sensor with a built-in amplifier.
• Regardless of the type of sensor, cables can also act as antennas for electromagnetic noise, so try changing the direction or route.
• Use a zipper tube to shield the entire wiring and ground it.
• Do not wire parallel to the power line. Use a separate route for wiring, and if they must cross, do so at right angles while keeping as much distance as possible.

Reference "Vibration Measurement" Simple Operation Manual PDF for DS-2000
Reference "Vibration Analysis Procedure" Simplified Operation Manual PDF for CF-7200

When an accelerometer is installed, the mass of the workpiece increases (mass effect), which causes the natural frequency to decrease. The mass of the detector should be kept to about 1/50 or less of the workpiece mass.

Reference "The effect of the weight of acceleration pickup on the measurement target"

The method of fixing the accelerometer causes differences in frequency characteristics due to the effects of contact resonance. It is important to choose a rigid fixing method as much as possible.

Reference "Regarding the Method of Fixing Acceleration Pickup"

When an accelerometer is installed at an angle, the cosine component of the actual vibrations will be detected, resulting in a smaller value, so please be cautious.

Reference: "What happens to the output when the vibration pickup is installed tilted against the vibration surface?"

In addition to the spectrum and time-domain waveform of the FFT analyzer, please recheck the AD over, input level indicators, and, in the case of charge-type accelerometers, the level indicator of the charge amplifier to ensure they are set to appropriate levels. Do not rely solely on the display screen of the FFT analyzer for judgment. (In particular, when measuring shock vibrations with small detectors, the FFT frequency range may be too low, causing you to miss large vibrations near the detector's resonance frequency. Additionally, be cautious as significant vibrations may also be detected above several tens of kHz.)