Profibus Terminating Resistor

[rngtech]

Hi all,

We are installing a number of Profibus actuated valves (Auma AC 01.2). They have a terminating resistor on the PCB but the system integrators have decided not to use the built in terminator and have instead proposed to use a Siemens active termination module 6ES7972-0DA00-0AA0.

Do these active powered modules provide any benefit in comparison to the standard terminating switch built into the Valve, or will they both perform the exact same?

Thanks.

 

[JesperMP]

The active terminators has an external 24V power supply.
If the 24V is supplied from an external source, it will keep the bias voltage for the termination active, also when the devices are shut off.
The termination in the auma drives will lose the bias voltage if the power supply to the drive is shut off.

 

[cardosocea]

They seem to need a separate power supply, so perhaps it's a form of repeater for the remaining network?

Have you asked the system integrators why they're doing this?

 

[John.S]

As Jesper pointed out... the first and last slave (physicaly) on a profibus segment has to be terminated, and that needs a supply voltage that is supplied by that device.
When you use an active terminator, the Profibus will stay alive when you switch of one of these devices. Except if one of these is the Profibus master of course.
All the slaves in between that 2 devices at begin and end can always be safely turned off, but when you don't use the active termination modules you can get in trouble when switching off one of the devices that are located at either end of a segment.

john.

 

[JesperMP]

No they do not have any electronic function, apart from the bias voltage for the termination resistors.
The intended use is to place them at the very ends of a profibus segment, where you cannot guarantee that all profibus devices are allways powered up.

 

[AlfredoQuintero]

I recommend that during commissioning either the Procentec's Profibus analyzer tool or the Softing BC-700 tool be used to certify the network. Verify that the idle voltage is 1.1 V. If it is not, this is an indication of wrong termination.

 

[Ken Moore]

A termination resistor is required on the last POWERED device. If you remove the connection from the last valve, it may cause network issues. As an integrator, I always recommended the active termination module. It saves a lot of, unexpected, middle of the night production issues.