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Tachometer circuit using integrated speed voltage converter LM2907

Published on Jan 07 2011 // Acceleration and Speed Sensor Circuits

Tachometer circuit using integrated speed voltage converter LM2907

Posed by the LM2907 tachometer circuit as shown. Using magnetoresistive speed sensor for speed signals. Tooth plate fixed to the rotating shaft to the gear plate processing has 60 equally spaced teeth. Contains a permanent magnet inside the sensor and induction coil, it and the chain adjusted to the gap of about 1mm. When the tooth plate rotates, the gap at the reluctance to change can be induced in the coil out of electrical pulse signals. Tooth plate per revolution, the sensor 60 to send electrical pulses. f through the A1, the complete use of the charge pump frequency / voltage conversion. C1, R1 and C2 is the charge pump external components. R2 is the output resistance. RP is the frequency calibration potentiometers. C3 is the filter capacitor.
Magnetoresistive sensors can be used as a 800O input impedance Ear buds converted. If the teeth are inlaid in each piece of permanent magnet, it becomes a magnetic sensor. Also can be applied to photoelectric, Hall element speed sensor. The circuit is R1, C1 fixed, only to change the input signal frequency. In addition, you can also change the fixed time constant input frequency f = R1C1, the output voltage is proportional to Uo and t. This can be divided into the following two cases to be discussed: (1) using the measured capacitor Cx to replace C1. When the fixed R1, Cx change, there is relationship UaCx. Using this principle may constitute a multi-range analog capacitance table. (2) The measured resistance Rx to replace R1. In the fixed-C1, R1 changes, there are relationship UoaR1. Which may constitute a multi-range linear ohmmeter, still used as a 10V DC voltage meter indicator.