Measurement mode

Four measurement mode algorithms can be selected to suit your measurement application

Rpm measurement
of the motor

Rpm measurement 
from vibration

Rpm measurement
from the magnetic leakage

■ Using a microphone or an accelerometer to measure the rotational speed of an engine

The rotational speed of an engine can be measured by the sound or vibration caused by the movement of the pistons. This is an effective measurement method when the engine compartment is covered, and engine rotation sensors cannot be attached.

• Set the number of pulses to match the number of ignition firings per one crankshaft rotation.
  Example: In the case of a four-cylinder engine with four-cycle, the number of pulse is set at 2 P/R.

■ Measuring the rotational speed of DC motors incorporated into home appliances

This example shows how to measure the rotational speed of DC motors that are built in the home appliances. Even if the DC motor has been installed deep inside an appliance such as an electric toothbrush, the rotational speed can be obtained by the magnetic flux leaking from the motor.

• The rotational speed can be measured simply by inputting the number of poles in the DC motor rotor.

■ Using an engine rotation sensor to measure the rotational speed of an engine

The rotational speed of an engine can be measured by clamping a sensor to the primary low-voltage or secondary high-voltage conductor. Measurement can be performed simply by inputting the number of ignitions per rotation.

• Set the number of pulses to match the number of ignition firings per one rotation.
  Example: In the case of a 4-cycle engine If you will be performing measurement on the primary conductor, set the number of pulses to half the number of cylinders. If you will be performing measurement on the secondary conductor, make the setting 0.5 P/R so that there is one pulse for every two rotations.

■ Using an accelerometer to measure the rotational speed of a small fan

This example shows how to measure the rotational speed of rotating objects such as a small fan. The vibrations from a rotating object depend on the rotational movement of that object. The rotational speed of an object can be obtained by measuring the vibration frequency.

■ Using an accelerometer to measure the rotational speed of a compressor

This example shows how to measure the rotational speed of the compressors that are used in air conditioners and similar equipment. When used in combination with an accelerometer, the FT-7100 can be used to measure the rotational speed of a compressor whose rotational shaft is not directly accessible.

■ Using a microphone to measure the rotational speed of an engine from the muffler noise

This example shows how to measure the rotational speed of an engine from an automobile's muffler noise. Since the pulsation component of the engine rotation is included in the muffler noise, the engine's rotational speed can be obtained by this pulsation frequency component.

• Set the number of pulses to match the number of ignition firings per one crankshaft rotation. Please note, however, that depending on muffler performance, there may be cases when measurement cannot be performed.