What is the Tachometric dynamo sensor?

What is the Tachometric dynamo sensor?
A dynamo is a voltage generator. Converts mechanical energy into electrical energy.
If we place a loop of wire of a conductive material, able to rotate freely, in the magnetic field between the opposite poles of two magnets, and make it rotate, at the open ends of the loop we can measure a voltage proportional to the field strength magnetic, loop area and angular velocity. The principle of the tacho dynamo is based on this principle. It consists of two opposite semi-cylindrical magnets and a coil capable of rotating inside. Using a collector and a brush system, the output voltage is collected.

tacho dynamo

Tachometer dynamo connected to a motor
When the dynamo is mechanically coupled to a rotating shaft, it delivers a tension proportional to the angular velocity of the axis ω. Based on this principle, this component is used to measure angular velocity. Its main application is the measurement of the turning speed of anemometer motors etc.

dynamo motor

Types of tachometric
We can find two types of tachometric dynamo, one delivers a pulsing direct voltage at its output, with a frequency and magnitude proportional to speed, and others that give a continuous voltage, proportional to speed. The latter does not require a very complex conditioner since a filter is enough to eliminate the ripple and an amplifier.

The former requires a more complex signal conditioning circuit, on the other hand, the frequency can be used as a measurement parameter with a voltage-to-frequency converter circuit. This option offers good measurement accuracy although the response time is longer due to the electronics.

Measurement
In the case of a dynamo whose output is DC, the conditioner is very simple. An RC filter and an amplifier are enough. With the pulsing output dynamo, we can rectify (smooth) the output and apply the same circuit.

tachometric dynamo measurement

We can also use a more complex signal conditioner, such as a frequency to voltage converter. A voltage frequency converter can be implemented around the LM2907 integrated circuit

dynamo frequency