This measurement column addresses frequently asked questions received by our customer support center and provides answers to those questions.
In detectors that output change amounts as pulse signals, such as rotary encoders, linear encoders, and flow meters, the pulse signal from the detector is converted into a physical value on the measuring instrument side and displayed numerically.
This time, we will introduce an example using the event counter function and F/V converter function, which can convert pulse signals into physical values.
While Oscope's F/V converter specializes in rotational speed, it can also convert other pulse signals from "frequency" to distance, speed, flow rate, etc.
Using a pulse signal from a linear encoder as an example, let's calculate the distance traveled (event counter) and the instantaneous speed of movement (F/V converter).
For flow meters, this would include cumulative flow rate and instantaneous flow rate. It's a function with a wide range of applications.
Each pulse signal represents a movement of 0.5 mm.
If 100 pulses are output, the travel distance is 100 × 0.5 mm.
It will be 50 mm.
This is a signal waveform. The movement speed gradually increases, then remains constant, and finally slows down.
(A higher sample frequency during recording improves the resolution of the F/V converter.)
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pulse waveform
1. How to view the distance traveled (cumulative value) over time using the event counter function.
Select Event Counter from the Signal Processing menu.
Set the initial count value to 1 and the count step value to 1.
Select the conditions file and click [button].
In the search criteria settings
Condition type: Level trigger
Trigger level: Approximately 50% of the pulse waveform amplitude.
Hysteresis: A value smaller than the trigger level (small changes are ignored).
Click the [OK] button to return to the event counter screen, and then click [Execute].
New data will be created. It will appear in the Data Manager.
Here, it's still showing the pulse count value.
Each pulse results in a travel distance of 0.5 mm,
Multiplying the count value by 0.5 will give you the distance.
We will use the simplified calculation function.
Set * and 0.5 in the calculation formula.
Check the unit conversion option, set the unit name to mm, and click [Execute].
The value has been converted to a distance value.
Reading the cursor value reveals that it has moved 74 mm.
2. How to view instantaneous speed using the F/V converter function
Select the F/V converter from the signal processing menu.
The F/V converter is designed for converting rotational speed, but it can also be used to convert other signals.
One important point to note is that the rotational speed unit is r/min, so calculations are performed using the value per minute.
The setting is: conversion type Pulse
Pulse/Rotation: This is where you set the number of pulses per revolution,
This is the number of pulses per 1 mm and the distance traveled per minute.
In this example, 2 × 60 = 120 (2 pulses per 1 mm, 60 seconds).
Level: Approximately 50% of the pulse waveform
Hysteresis: A value smaller than the trigger level (small changes are ignored).
Clicking [Execute] will create the data.
Where the pulse interval changes, the magnitude changes, allowing you to observe how the speed changes during movement.
The unit name is still listed as r/min.
Change this to mm/s.
Select Channel Settings from the Data Processing menu.
Enter "mm/s" as the unit name and change the signal type to "Speed".
Now the display shows the movement speed (mm/s).
As shown above, if it's a pulse signal, the physical value can be easily obtained using Oscope's conversion function.
After this, it will be possible to perform fundamental frequency analysis to determine the fluctuating frequency.
While it's not possible to view physical values in real time, recording pulse signals allows for various secondary processing analyses later on.
If the signal is a pulse signal from a flow meter, the cumulative flow rate and instantaneous flow rate can be determined.
If you can record pulse signals such as rotation, distance, flow rate, and torque, there are many situations where the Oscope can be useful.
(Excerpt from the email newsletter issued on October 23, 2019)
