FV Converter Frequently Asked Questions

When a reflective sticker is attached to the shaft and the signal is detected by a photoelectric detector such as the LG-916 or LG-930, the number of pulses per second is low, and depending on the rotational speed to be measured, it becomes extremely low relative to the frequency range of the FV conversion circuit, resulting in the output voltage as described in the question.

<Explanation>
The TM-2130 and FV-1100 utilize an FV conversion circuit (frequency/voltage conversion circuit) to convert the input signal into a voltage proportional to its frequency. The integrating circuit charges when the input pulse is high level and discharges when it is low level. As the frequency of the input pulse increases, the number of charging cycles increases, and the overall charging time increases, so the output voltage rises. Conversely, as the frequency decreases, the discharge time becomes longer than the charging time, and the output voltage decreases.
The charging and discharging speed increases with a smaller time constant, and the difference in charging and discharging voltage (ripple) per pulse becomes larger. This ripple is negligible at high input frequencies, but becomes larger at lower frequencies.
Photoelectric detectors like the LG-916 and LG-930 only produce a signal for each reflective sticker attached per rotation, so the input frequency tends to be low, leading to the situation described in the question. You need to calculate the input frequency from the operating rotation speed range and check whether it can be used at 10% or more of the frequency range of the FV converter.
The TM-2130 catalog lists the output voltage ripple when the frequency is at 1% of the frequency range.