Since the inception of the Class (or Type) A and Class (or Type) B ports in the IO-Link specifications, there have been several new IO-Link devices and IO-Link masters introduced to the market. This has caused a lot of confusion about when and where to use Class A and Class B IO-Link masters and devices.
Before getting into the details of Class A vs. Class B, I would like to address one question that I get asked quite often: are Class B master ports safety-rated? The answer is no. Just like any other network I/O modules (with the exception of the Safety I/O modules), any type of IO-Link master (whether it is Class A, Class B or mixed) is not safety rated. If the block is safety-rated, I am certain that the manufacturers of these blocks will kindly let you know. So, we just busted the first myth about Class B ports. Side note: the IO-Link Consortium just released a specification for IO-Link Safety. At the time of this posting (Oct. 2017), there are no IO-Link masters on the market that are safety rated, even when the IO-Link master ports exist alongside Safety I/O parts on the same block.
For IO-Link communication, only pins 1, 3 and 4 have significance. The implementations of pin 2 and 5 is where Class A and Class B ports differ and with that, the advantages and disadvantages of the uses for these ports.
Clearly, with the wiring diagrams above, a Class A port offers more flexibility in terms of additional I/O count and in some cases high-amperage outputs to drive high-current devices such as valves. We will discuss the detailed power routing and application flexibility of Class A ports in a later blog.
With Class B ports, Pin 2 and Pin 5 are tied to a separate power source and cannot really be used as I/O. Pin 5, the ground for output power, is separated from pin 3, the ground for device power. Actuation devices, such as valve banks, that are now offered on IO-Link could utilize separate output power that can be turned off through safety relays. Technically, this separation of power is possible with Class A ports as well, but it is inherent with Class B ports.
A word of caution when implementing I/O architectures with Class B masters: since the commons for device power and output power are isolated at the master, the power fed to this device should be isolated at the source as well to keep the isolation intact. That means, the power supplies feeding the power to these devices should be isolated.
Another question that I get asked frequently reveals another myth about Class B master ports: do Class B master ports offer any extra power than Class A ports? Again the answer is no. Class B does not mean extra power or the ability to provide more power. It simply means output power with isolated commons. What leads to that thinking is that on several IO-Link masters in the market, the outputs available on pin 2 of Type A ports have lower amperage ratings, because in most cases the output power is shared or drawn from the same source that feeds device power. There will be more discussion about this in my next blog!
A third interesting question is, can you plug Class A IO-Link devices into Class B master ports? In most cases there is no problem doing this as a true IO-Link Class A device is only a 3 pin device using pins 1,3, and 4 shown above. So as long as pin 2 of the device does not exist or is not being used for any purpose, it is possible to use Class A devices with Class B ports. Caution: several manufacturers make sensors that can be used in IO-Link mode as well as analog or digital mode and the implementation may have more than 3 pins. In these circumstances, you will need to use a 3-pole cable to keep the device unharmed or the pin 2 of the type B port that always has +24V going through may damage or disrupt the sensor.
Meanwhile, I hope this blog helped provide some clarity on Class A and Class B ports.
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extending the full length of the mechanical stroke. A magnet ring is used as a position marker and mounted on the face of the piston. As the piston (and the position marker) move, the linear position sensor provides a continuous absolute position by way of an analog or digital signal.
offerings as a go-to as they seem more common. Photoelectric sensors are solid performers, however they can run into limitations in certain applications. In these circumstances, considering an ultrasonic sensor could provide a solid solution.
customer needed to detect a few features on a metal angle iron. The customer was currently using a laser photoelectric sensor with analog feedback measurement, however the results were not consistent or repeatable as the laser would simply pick up every imperfection that was present on the angle iron. This is where the ultrasonic sensors came in as they provide a larger detection range matched with emitting and receiving sound energy. This provided much more stable outputs, allowing the customer to reliably detect and error proof the angle iron. With the customer switching to ultrasonic sensors in this particular application they now have better quality control and less downtime.
to think of all sensor technologies as some will provide better results than others. Ultrasonic sensors are indeed an excellent choice when applied correctly. They can measure fill levels, heights, sag, or simply monitor the presence of a target or object. They perform very well in foggy or dusty areas where some other sensor technologies fall short.
two primary objectives for Balluff’s work in the area of Industry 4.0 are to help customers achieve high production efficiencies in their automation and achieve ‘batch size one’ production.
Machine Geeks 