Question regarding Ethernet/IP vs Analog I/O

toddp65

Member
Join Date
Aug 2014
Location
Florence, Ky
Posts
280
This may be a simple question.
I understand the concept and application of analog modules (i.e. Compactlogix) for transducers, and outputs for VFD speed reference and such but my question is regarding the use of Ethernet/IP for the analog. For example we have a couple Ethernet based SICK encoders that do not report to a HSC module--there isn't one on the rack and Drives are speed referenced thru Ethernet as well....does this indicate the analog and signals are traveling thru the Ethernet and these modules are not necessary as the code is being handled in the controller without the dedicated module interface of a HSC or Analog input/output modules?
 
Yes and no. The actual analog SIGNALS are not being transmitted in the Ethernet media. The analog values are being converted to digital values, and those digital values are what is transmitted within a packet of data from device to device. Since whatever needs that information was going to convert analog to digital internally anyway, it ends up the same and in fact can acutually avoid errors in transmission of the analog values over long distances. In your example if the SICK encoder has an Ethernet I/P output port, that means is had the transducer (HSC) built-in that is doing the converting to a digital value right at the encoder and making it available to the Ethernet I/P network.
 
Ok--so there's no actual analog travelling thru the Ethernet because, well, it's not capable of doing so, therefore the PLC is receiving digital data. So am I correct in assuming that control of a VFD, i.e. a Powerflex 525, the speed reference can be transmitted without an analog ouputt card and an analog output from the drive (amperage) does not need an analog input card-- so basically a controller without those modules is capable of performing these tasks?

thanks
 
Ok--so there's no actual analog travelling thru the Ethernet because, well, it's not capable of doing so, therefore the PLC is receiving digital data. So am I correct in assuming that control of a VFD, i.e. a Powerflex 525, the speed reference can be transmitted without an analog ouputt card and an analog output from the drive (amperage) does not need an analog input card-- so basically a controller without those modules is capable of performing these tasks?

thanks

Yes. Generally you can control every parameter of a drive... so not only the speed reference but the mode (speed versus torque control) and torque, current limits, etc...

You usually can also retrieve a lot of information from the drive such as faults and fault codes that can make it simpler for maintenacne to troubleshoot the system.
 
Thanks--I was aware of that as I've added a 525 to a project before--I was just hazy about the interaction between an ethenet/ip device such as a drive or encoder or anything else analog (I've seen summing boards for scales) and the need or lack of a need for dedciated analog cards.


Thanks
 

Similar Topics

I know this can be done, but I can't get the router config right. My goal is to physically connect(using an ethernet cable) a device(PLC, RTU...
Replies
9
Views
976
I haven't had to tune a PID loop in a very long time. It's actually a PI loop for a pulse width modulation s.v. What was the name of that tuning...
Replies
16
Views
4,073
Hello, I have a question regarding the analog output modules on a AB Micro850. I'm not getting an output to my valve and when I put a meter on it...
Replies
2
Views
1,526
Happy new year everyone. This is more of a Electrical engineering question than a PLC one. Can a Motor and a VFD that is rated for 240/480...
Replies
29
Views
9,619
Good Evening, I am curious to know, if its possible to use PlantPax graphics, face plates in Factory Talk View without utilizing its Add On...
Replies
6
Views
2,194
Back
Top Bottom