can i use one analog output to control two VFD's?

I have a siemens s7-200 plc with an EM235 analog I/O unit with one analog output. At the moment this output is controlling the frequency of one allen Bradley 160ssc VFD. I want to control another 160ssc so that it mirrors the frequency of the first one. There is no analog output on the 160ssc that I can use to cascade the second VFD and I don't have another analog output on the PLC, is it ok to use the same anlog output from the EM235 for both VFD's? or does each one need its own output? (I think it would work ok linking the same output to both VFD's, but I want to know if it is acceptable practise to do this)

Yes it will be fine to use the one output to the two drives. How the signal gets there is up for debate...
If it's a voltage output just wire the drive analog in's in parallel.
If it's current wire them in series.
I would recommend paying special attention to the screening of the cable through the joins
The purists will say to use a signal splitter or signal isolator. It's depends on the application.
If the drives reside in the same panel and are share a common ground and are fed form the same 3 phase bus then you will be ok with out isolators or a splitter. If they are in different panels, I would consider a splitter or isolator.
Opinion form a young senior sparky! Enjoy.

the analog output is 0-10v, and the VFD's are in seperate panels.

I would use an isolated splitter.
Attached is a unit I would recommend to any client in Australia with your specific application.

If the ss160 drives have isolated inputs, then simply parallel the two voltage inputs with the 0-10V signal.

Take a look on Phoenix Contact type MCR-FL-C-UI-2UI-DCI

It is a analog multiplier for doubling and electrical isolation of analog signals.

Order No.: 2814854
Order key: 2814854/U/0/10/OUT03/OUT03/NONE

hi guys, thanks for the replies. Thanks for the links to the splitters, i can't find anywhere to buy the australian one in the UK but I can get the Phoenix one from Farnell. What I want to know though is do I need to use the splitter? If it wouldn't work to just connect the VFD's in parallel or it is unsafe or considered bad practise, I will fit a splitter. But if that is not the case I would prefer to save the £180.

yes it will work without splitter as this input is in the drive optocoupled.

Not a problem so long as the VFD speed reference inputs are isolated.

The 160SSC analog inputs are isolated by the way.

One word of caution; differences in circuit resistance will exist, which need to be compensated for. So calibrate the analog input at each drive separately once it is all installed.