What is the difference between US and UA Voltage?

alive15

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Oct 2015
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Good afternoon to all,

What is the difference between US and UA voltage? I will use US voltage on this cable (brown and blue wire), but wanted to know what the differences between the two were?

See yellow highlights in attached image.

Thanks!

us vs ua.JPG
 
Mentally replace "U" with "V" for Voltage on European pinout diagrams.

This is a "T-coded" M12 quick disconnect, meant for DC power up to 63 volts.

My guess is that "Vs" is the Supply voltage, while "Va" is... analog ? Application ? Anythingelse ?

Edit: In this context Padees is exactly correct. I've seen other devices call "Vs" the Supply voltage, but in this context where you have both Inputs and Outputs, the "Vs" is for the input Sensors and "Va" is for output actuators.
 
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Thanks for the info. I can understand Vs as supply voltage, but not sensor supply.

I don't understand what UA or VA is and when I would use this, I am just putting wire nuts on these two for now (black and white wire). But in what application will I use the UA or VA wires?
 
That IFM IOLink block can have both input and output devices connected to it.

If you look at the IFM specifications page you'll see that it lists the Operating Voltage as 20-30 V DC and mentioned "SELV" and "PELV", which are types of low-voltage power supplies common in Europe.

It also lists the "additional voltage supply (UA)", which is your output power supply.

Having separate pairs of pins on the power connector allows you to connect a different voltage source for your outputs versus your inputs.

Typically you want to do that when your application requires a specific power limit for the cabling, or if you want to segregate your outputs from the IOLink block power itself so that if there's a short circuit or blown fuse the whole thing doesn't go down.
 
In addition to what Ken stated, the output power can be wired to an E-Stop thru the main power cable if you need to drop the outputs out. That will also have 2 separate sources.
 
Ah, I see how it works now. When I first read "UA is an output, for like a solenoid valve", I thought you were saying 24VDC+ is coming out from my I/O link from the "power in" port. I was very confused for the past 15 minutes.

Anyways, please check my understanding --> Both UA and US are +24 VDC inputs from my power supply, but UA powers my output ports while US powers my input devices into the I/O link, such as proxes, laser sensors, etc.

I see why you would want to separate power between inputs and outputs; the UA is similar to having like a Master Control Relay or Control Power, correct? So when the UA or the Control Power is turned off, I would have no outputs on like in a PLC output card, but my input devices will still have power to them so I will still see the inputs on in the PLC input card. Correct??

Thanks,
 
The letter "U", often used to denote voltage supply, is said to be derived from the German word "Unterschied" which means "difference". This loosely implies "voltage difference" which may be used to help understand the meaning of the use of the letter "U" for the power supply to these types of electrical equipment.

For the IFM IO-Link Master devices, a distinction is made between two supply voltages:

– US to supply the communications power and the sensors (always required)
– UA for supplying the actuators, only required for devices with fixed outputs or for additional devices

Power supply US is required to supply the communications power of the device electronics and to supply the sensors.
It must be connected to every device. If this supply voltage is disconnected, the device will not work.

This is the recommended installation wiring method:

- Install the power supply for the device electronics (US) independently of the power supply for the actuators (UA)

- Protect the power supplies independently. This means that the bus can continue running even if some I/O devices are switched off.

The voltage supply UA is only required for the supply of the IO-Link actuators. The IO-Link port, when in the operating mode "DO", is supplied via US. If an IO-Link device is not using any actuators then the supply UA need not be connected.

As mentioned, it is good practice to separate these supplies so as to better protect the more sensitive device electronics and communications bus on US from the potentially higher current rated actuator devices on UA.

However, I have seen quite a few of these installed with a single power supply connected to both US and UA, especially when the power supply is local to the IO-Link device enclosure, where space is often at a premium.

alive15 said:
...I see why you would want to separate power between inputs and outputs; the UA is similar to having like a Master Control Relay or Control Power, correct? So when the UA or the Control Power is turned off, I would have no outputs on like in a PLC output card, but my input devices will still have power to them so I will still see the inputs on in the PLC input card. Correct??...

The manufacturer's advice to protect sensitive electronics, by use of independent powers supplies, is the primary reason for the option being available, more so than facilitating auxiliary functions, such as isolation of outputs while inputs remain on, or ad hoc safety isolation. I'm not saying you cannot use this option for such things, but just that it is not its primary reason for existing.

Regards,
George
 
Last edited:
Thanks for the in-depth info George. Yeah, that makes sense that safety of the electronic devices is promoted as the primary reason.

Thanks again for all the replies.
 

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