Accelerometer Frequently Asked Questions

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

(Note)
If a locking washer is present, there may still be some play in the connector even after tightening it firmly. The washer may become extremely compressed, but it is necessary to tighten it until there is no more play.

We will check by replacing it with a spare cable. Depending on the model, this can be checked using the CCLD function's cable break detection feature.

Ensure that the CCLD is enabled in the sensor amplifier/FFT analyzer settings. Additionally, you need to select a current value that matches the sensor specifications.

(Note)
The input connection must always be AC. With the CF-7200 analyzer, the CCLD automatically turns OFF when the detector is disconnected, so be sure to turn the CCLD ON again when reconnecting it.

Caution is advised when using the NP-0021 miniature/BNC conversion adapter. Depending on Accelerometer, the thickness of the rubber gasket included with the NP-0021 may prevent proper insertion, resulting in poor contact. In such cases, remove the rubber gasket before use. In particular, be sure to remove it when connecting to the NP-3211 Accelerometer.

Details: "The signal from Accelerometer seems to be occasionally interrupted, sometimes resulting in a disconnection being detected or no signal being emitted at all."

Secure the cable firmly in a way that prevents any undue stress from being applied to it.

Especially when using a charge output type Accelerometer, static electricity noise is easily generated within the cable if the cable itself vibrates, so make sure to secure it firmly to prevent vibration.

Rapid temperature changes can cause distortion due to thermal expansion of the sensor case, resulting in low-frequency noise (pyroscopic effect). Take care to avoid direct exposure to wind or radiant heat from heat sources such as incandescent bulbs.

• Ensure that the object being measured, the sensor, the sensor amplifier, and the FFT analyzer are properly grounded. (If the grounding is solid, this method is the most noise-resistant. Even if you connect the grounds of each piece of equipment to the factory's ground terminal, ground loop noise may occur if the main factory ground is weak.)
• Disconnect the ground on either the measurement system or the sensor amplifier/FFT analyzer. (If the grounding is not secure, a ground loop will form. In this case, to break the ground loop, you will need to either disconnect the ground on the measurement system using a float (insulated) type sensor or an insulated stud (available by special order; please consult your nearest sales office), or disconnect the ground on the sensor amplifier/FFT analyzer.)

(Note)
In this case, the sensor amplifier and FFT analyzer must be properly grounded. Insulated studs are available as a custom order. Please contact your nearest sales office for details.

• Let's try changing the sensor's mounting position.
• Try increasing the distance using insulated studs, etc. (Insulated studs are available by special order. Please contact your nearest sales office.)
• Since the built-in amplifier type is susceptible to interference, try switching to a charge output type sensor.

• Charge output type sensors transmit signals with high impedance, making them susceptible to picking up noise during transmission. 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 their direction and route.
• Shield the entire wiring with a zipper tube or similar material and connect it to a ground.
• Do not run parallel to power lines. Run separate routes, and if crossing is unavoidable, ensure the crossing is perpendicular to the power line. Also, keep the distance between them as large as possible.

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

Attaching an acceleration detector increases the mass of the workpiece (mass effect), which lowers the natural frequency. The detector mass should be approximately 1/50th or less of the workpiece mass.

Reference: "What effect does the weight of Accelerometer have on the object being measured?"

The method of mounting the accelerometer can affect the frequency characteristics due to contact resonance. Choose the most rigid mounting method possible.

Reference: "Regarding the method of fixing Accelerometer "

Please note that if you mount the accelerometer at an angle, it will detect the cosine of the actual vibration, resulting in a smaller value.

Reference: "What happens to the output when a vibration pickup is mounted at an angle to the vibrating surface?"

In addition to the spectrum and time-domain waveforms on the FFT analyzer, re-check the AD overload, input level indicator, and, in the case of charge-type accelerometers, the charge amplifier level indicator, and adjust them to the appropriate levels. Do not rely solely on the FFT analyzer's display screen. (Especially when measuring shock vibrations with small detectors, the FFT frequency range may be too low, causing large vibrations near the detector's resonant frequency to be missed. Also, be aware that vibrations large than several tens of kHz may be detected.)