Ono Sokki 's RP-7400 roller encoder can measure distance and speed by bringing a roller into contact with the object being measured. This article explains, based on the measurement mechanism, why it has pulse outputs such as 120 P/R and 1,200 P/R for speed measurement.
Velocity is the distance traveled per unit of time, so it is calculated as: Velocity = Distance Traveled / Time Taken.
When measuring line speed with the RP-7400 roller encoder, the distance traveled equals the amount the roller rotates, so the speed can be written as: Speed = Distance per pulse × Number of output pulses / Time taken.
What is the speed in millimeters per second?
The latter part of the equation representing speed, output pulse count/time, is the number of output pulses per second, so it equals frequency.
Therefore, the formula for speed (mm/s) = distance per pulse × number of output pulses / time is,
This can be written as (Roller circumference (mm) / Number of pulses per roller rotation) × Frequency.
If the ratio of circumference (mm) to pulse count is "1", then the output frequency from the encoder and the peripheral speed will be the same value.
Since the RP-7400 has a circumference of 200 mm, if you select a 200 P/R unit, you can use a frequency counter to display the peripheral speed (mm/s).
Also, by using a pulse counter to measure the number of pulses that arrive in one second,
Since the count directly corresponds to the frequency, if you have a pulse counter with a 1-second gate function, you can determine the peripheral speed from the frequency.
*Note that in this case, the measurement resolution is in 1 Hz increments, so the velocity resolution is also 1 mm/s.
What is the speed in meters per minute?
As expected, the speed (m/min) can be calculated using the formula: Speed (m/min) = Distance per pulse × Number of output pulses / Time taken. However, note that the units of length and time are different from those used previously.
In the first part of the formula, distance per pulse = (200 / number of pulses per roller rotation) / 1000,
In the latter half of the formula, output pulse count / time = output pulse count per minute = frequency × 60,
Therefore,
Speed (m/min) = ((200 / number of pulses per roller revolution) / 1000) × frequency × 60
You can write it like this.
Furthermore, if we combine the numerical parts...
Speed = ((200 × 60 / 1000) / number of pulses per roller revolution) × frequency
= (12 / number of pulses per roller rotation) × frequency
You can write it like this.
If the number of pulses per roller rotation is 1x, 10x, 100x, etc., then the speed can be expressed as 1x, 1/10x, 1/100x, etc., of the frequency.
Using the RP-7400 120 P/R,
Speed (m/min) = frequency × 0.1
RP-7400 1200 P/R
Speed (m/min) = Output frequency × 0.01
You can measure the peripheral speed (m/min) using a frequency counter or a pulse counter with a 1-second gate.
In the case of a pulse counter with a 1-second gate, the measurement resolution is 1 Hz increments, therefore the velocity resolution is:
Using 120 P/R results in a flow rate of 0.1 m/min.
Using 1200 P/R results in a flow rate of 0.01 m/min.
Depending on the required speed unit, select either a 120/1200 pulse or 200 pulse roller encoder.
bonus
The size of the periphery ring is determined using a similar calculation method when measuring periphery speed with the HT-3200 and HT-5500.
The basis is
The formula for speed (m/min) is: Speed (m/min) = Distance per pulse × Number of output pulses / Time taken.
In the case of HT, the number of pulses per revolution is fixed at 1,
The distance per pulse is the circumference of the circumferential ring.
The ratio of output pulses to the time elapsed is given by the rotational speed (r/min).
It will be.
If the circumference of the periphery ring is 1 m, the rotational speed displayed will be the same as the periphery speed.
In the case of the HT-3200, by using the KS-200 peripheral speed ring with a circumference of 100 mm and converting the displayed value to one-tenth, the peripheral speed in m/min can be read.
If you want to measure in mm/s,
The ratio of output pulses to the time elapsed is calculated as rotational speed (r/min) ÷ 60.
Using the KS-100 with a circumference of 60 mm, you can read the peripheral speed in mm/s by directly reading the displayed value.
(Excerpt from the email newsletter issued on December 18, 2019)
