Pepperl+Fuchs Blog

Speed Monitoring Options Using Industrial Sensors

Posted by Sean Miller on Tue, May 14, 2013

In certain applications with spinning components, keeping track of the speed or revolutions per minute is vital for controlling equipment and processes. Pepperl+Fuchs offers several solutions to achieve this.

Industrial Sensors for speed monitoringThe first item that you will need is a sensor. To continuously monitor shaft speed, you will need a gear end or target that rotates with the shaft. This speed detection method counts the number of on and off pulses, and requires a target that rotates with the object . An inductive sensor is the most common type of sensor used in this case, as most targets are steel and the cost of the sensor tends to be very low.

Another option for speed monitoring is using a photoelectric sensor to count the pulses. A setup for an inductive sensor might not be possible depending on target size and sensing distance. In cases such as this, a photoelectric sensor is an ideal solution, as most have a high switching frequency and good sensing range.

Rotary encoders are another common solution for speed monitoring. They are designed to connect to a rotating shaft and give pulse outputs as the shaft rotates. The number of pulses that the encoder gives off determines the speed. The number of pulses per full revolution of the shaft determines the resolution. We offer models up to 50000 pulses per revolution on incremental encoders and even higher on certain absolute encoders.

Another option for monitoring speed is the KFU8-FSSP-1.D, which is a frequency-to-voltage/current converter. This device is capable of giving a voltage or current analog output based on the frequency of discrete pulses that the unit receives from a sensor or an encoder. It accepts 2-, 3-, and 4-wire sensors. It has a built-in display to view the output or the speed in RPM. We also offer the KFU8-DW-1.D, which is an over speed/under speed monitor that has similar display capabilities as the KFU8-FSSP-1.D, but has a dry contact output. When a programmed speed is met or drops below a given speed, the output is triggered. This device can also take 2-, 3-, and 4-wire sensors as well as encoders.

Both units can measure speeds of up to 40 kHz. With such a high switching frequency, the sensor or encoder is usually the limiting factor in terms of the fastest measurable speed. Pepperl+Fuchs offers models with similar features to these with ATEX and approval for use in hazardous locations when paired with a NAMUR sensor.

A zero speed monitor is useful when you need to know the direction and zero speed of a shaft or other rotating target. To determine the zero speed, you will need at least two devices or sensors capable of giving a discrete output. Place these two devices or sensors close enough so the signals overlap. Overlap occurs when the signal from the first sensor remains on while the second sensor output is triggered. From this overlap, you can tell the direction of rotation. You can easily find the zero speed when no rotation pulses are being received.

You could also use speed monitoring sensors. For certain applications, a simple speed limit might be the only variable needed to control a process. We have limit switch style sensors with different frequency ranges. Our models ending in DW2-1 can be adjusted from 0.1 Hz to 1 Hz or about 6 cycles per minute to 60 cycles per minute. Our DW2-10 models can be adjusted from 1 Hz to 10 Hz or about 60 cycles per minute to 600 cycles per minute. Lastly, our DW2-100 models can be adjusted from 10 Hz to 100 Hz or about 600 cycles per minute to 6000 cycles per minute. The basic principle for operation of these speed sensors is that they will not give an output until the frequency of output state changes reaches a certain value. Then the sensor will give a discrete output. You can adjust the frequency range using a potentiometer located on the sensor. These sensors are offered in both DC and AC models. Currently, only a limit switch style is available. We do offer models with a startup override feature where the output remains on while the device it is measuring is taking the time it needs to reach operating speeds.

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Topics: Rotary Encoders, Inductive Sensors, Photoelectric Sensors

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