11-20-2006 01:44 PM
11-20-2006 02:40 PM
Dave,
I'll assume you are powering the cFP-AO-200 module with a 24V power supply. Use the same power supply to power the MFC. (Supply+, Supply -) Run the wires directly from the supply to the MFC. Do not daisy chain the MFC and the cFP-AO-200. Make sure that your supply has the capacity to run everything. The "hot wire" and valve in the MFC will require more current than most 4-20ma instruments. Wire the "out" of the cFP channel to the "setpoint" input of the MFC.
11-21-2006 08:04 AM
Thanks for the quick reply. I have a couple of additional questions:
1. If I connect as above, will this cause problems with my other devices? They have to draw their current from somewhere and wiring it up as above wouldn't all the current for the devices in the module will have to pass through the Sierra MFC?
2. I have two more of these MFCs for phase two of the project. Will they interfere with each other if I connect them to the same FP module? I have a 5A supply so I don't think lack of current will be an issue. I just don't want to inadvertantly cause a short or have the devices feedback through each other.
Thanks again!
Dave
11-21-2006 09:02 AM
Dave,
1. If I connect as above, will this cause problems with my other devices? They have to draw their current from somewhere and wiring it up as above wouldn't all the current for the devices in the module will have to pass through the Sierra MFC? -
I don't think you understood my answer. You need to run a separate Supply +,- from the 24V power supply to each MFC and to any other devices that are not loop powered. That includes the cFP-AO-200. It's sometimes refered to as a "star configuration". The power supply is in the middle and each device has a dedicated power feed/return directly from the supply. That means that the only power running through the cFP module is what is required to power the output signals on the "out" terminals. The return side of the output signals is already wired via the "Supply -" signal that is wired to all these devices.
Are any of your devices "loop powered"? If so, let me know what they are. Connections to those are just a pair of wires from the cFP module to the device.
2. I have two more of these MFCs for phase two of the project. Will they interfere with each other if I connect them to the same FP module? I have a 5A supply so I don't think lack of current will be an issue. I just don't want to inadvertantly cause a short or have the devices feedback through each other. -
No. The MFCs will not interfere with each other and you don't need to worry about feedback. With the cFP module and the MFC's sourced from the same power supply all the outputs and inputs of the devices are now referenced to each other via the common "Supply -" signal. The "star configuration" controls where all the different currents are flowing and keeps the cFP module from having to carry any more current than is necessary.
hope this helps
11-21-2006 09:15 AM - edited 11-21-2006 09:15 AM
Ah! Gotcha. You're right I did misunderstand your initial post. That explanation clears things up and makes sense.
There are some loop powered devices (MFCs and control valve actuators) so I will connect them as you explained above.
Thanks for the help!
Dave
Message Edited by Little Dave on 11-21-2006 09:17 AM
11-24-2006 09:12 AM
11-27-2006 07:34 AM
Dave,
Glad I was able to help. Thank you for the follow up.
It's always nice to know how things turned out.
Wayne