Tachometer Frequently Asked Questions

Using a detection gear (60 teeth), analog output corresponding to rotational speed can be obtained with the MP-981, MP-9100, and TM-2130. This document explains how to configure this. For settings related to the digital display, please refer to the separate instruction manual.

Note Ripple phenomenon (see Table 1) Due to the integrating FV conversion circuit, a ripple phenomenon occurs at low rotational speeds. Therefore, there is a lower limit to the measurement. The lower limit of measurement varies depending on the set frequency range and response, but please note that it should be used at 20Hz or higher as a guideline. With the LG-9 and LG-930 photoelectric detectors, using only one reflective sticker results in a low signal frequency and large ripple, so attention must be paid to the lower limit of the measurement range. Use with approximately 1000 r/min or higher when using one reflective sticker <ripple phenomenon>.

• The analog output is configured with a separate circuit from the digital display, so it is not affected by the settings related to the digital display.

• The analog output terminal outputs voltage (10V/frequency range) and current (4-20mA/0-frequency range) simultaneously, but there are conditions under which voltage output and current output can be used at the same time.

• Please refer to the instruction manual for details.

■Measurement conditions

The measurement conditions are as follows, and the explanation will follow.

• Gear tooth count: 60 (60P/R)
• Rotation detector: MP-981
• Measurement limit (full scale): 8000 r/min

■ Analog output settings

(1) Selection of frequency range

The maximum frequency of the input signal can be calculated using the following formula.

(2) Set the frequency range to "10kHz" to cover the maximum frequency.

As shown in Figure 1, set "Bit 2: ON" and "Bits 1, 3, 4, 5, 6, 7: OFF". The frequency range can be selected from seven ranges: 20kHz, 10kHz, 5kHz, 2kHz, 1kHz, 500Hz, and 200Hz. The selected frequency range becomes FS (full scale), and when the input signal has the same frequency as the selected range, a voltage output of 10V and a current output of 20mA are output.

(Example) When the range is set to 10kHz
When the input signal is 10kHz, the voltage output is 10V and the current output is 20mA. When there is no signal, the current output is 4mA.

The digital display shows a value corrected by the multiplier setting. Therefore, please note that you will need to convert the voltage output to read it as the displayed value.

(3) Setting the response

Bit 8 in Figure 1 sets the response time. There are two settings: "Bit 8: OFF (120ms)" and "Bit 8: ON (700ms)," which change the ripple. Please refer to the table below for the amount of ripple. When ON (response 700ms), the output will be smoother than when OFF (response 120ms). Set "Bit 8: OFF (700ms)" when using in a low frequency range or when an average output is desired.

Figure 1

Table 1: Ripple

<How to read the table>

(Example) Ripple when the frequency range is 10 kHz, the response is 120 ms, and the setting is 0.3%/FS (0.03 V)

Frequency range 1% = 10kHz × 1% = 100Hz

When the input signal is 100Hz, there is a ripple of 0.03V (10V × 0.3% = 0.03V). The ripple increases from 0.03V as the frequency decreases below 100Hz.

(4) Analog output specifications and wiring

(4-1) Analog output specifications

frequency range	20kHz、 10kHz、 5kHz、 2kHz、 1kHz、 0.5kHz、 0.2kHz
linearity	±0.3%/full scale
Output voltage	0-10V for each frequency range (load of 1kΩ or more)
Output current	4-20mA for each frequency range (load 500Ω or less) *Simultaneous output of voltage and current is possible when the voltage load is 100kΩ or higher.
Output ripple	It depends on the frequency range and response.
Output adjustment	Approximately ±5%/full scale (voltage), Approximately ±3%/full scale (current)
Zero setting accuracy	±0.5%/full scale (voltage output, room temperature) ±0.3%/full scale (current output, room temperature)
Zero Drift	±0.01%/full scale/°C
Spandrift	±0.025%/full scale/℃
response	Switchable between 120ms ± 20ms or 700ms ± 100ms

(4-2) Wiring method

Wiring should be done as shown in Figure 2. Use shielded cable, and ground the shield at the connection point.

Figure 2

(4-3) When using voltage output and current output simultaneously

When connecting both voltage and current outputs simultaneously, the input resistance of the connected device must satisfy the conditions shown in Figure 3.

Figure 3