Multiplexer

Hi guys.

I have spent the past few weeks on Google looking at various solutions to my problem below. Any help you can offer, would be very much appreciated.


Project:
I am currently have a panel spacing issue and am looking for some devices that others know of or are using. I am trying to monitor 50 AC currents (approximatley 0-20A at 240VAC). My idea for this is to convert each current to a 4-20mA DC signal and input that into a PLC. To do this, I would input each signal into the multiplexer linked below to reduce the number of inputs to my PLC.

http://www.omega.com/DAS/pdf/DRA-CSM.pdf

However, the downfall to this multiplexer (and all the other ones I can find) is that the inputs must be a DC signal. To reduce the number of devices and space, I am looking for a solution that would let me convert the VAC signals to 4-20mA DC AFTER the multiplexer thus only requiring one signal converter.

So, once again, the question is does anyone know of or use such a device? Thank you.



***On a side note, the converter I am currently looking at using is a signal conditioner that is 22.5mm wide. This width is just barely too big to fit in the cabinet space. I also cant seem to find a smaller one that would let me do the above conversion. If anyone has some suggestions, feel free to leave them as well. They do not have to be a signal conditioner. A transducer/Hall Effect monitoring device that is less than 22.5mm wide would also work wonderfully.***

Sounds fun: How's your electronics? You could make your own with SN74154 4-16 line decoder ic's, with their outputs operating into opto-coupled fets for each C.T. (eg Fairchild H11F1). Connect permanent load resistors to each ct so that the o/p from them is a voltage. Put all the CTs' outputs in parallel with one leg of each one connected directly to all the others and the other leg through its fet to the bus. The ct "bus" now goes into an RMS to DC converter (AD736) and off to the plc as a voltage. Parallel the addressing to four 74154s from a 4-bit binary signal from the plc and then use further individual outputs from the plc to enable each ic when it's that one's turn. So a bit of sequencing in the plc, but you were going to do that anyway. Use resistor packs to drop the plc's 24V o/p to 5V for the ics' inputs. No doubt it'd take a bit of tweaking but if it's your thing and you have some time, then try with a couple of channels first. But all those inputs into 22.5mm???

The multiplexer you listed handles 4-20 just use a current transducer like this that puts out 4-20
http://www.automationdirect.com/adc..._Transducers/AC_Current_Transducers_(True_RMS)

If you need one that is more flexible use this http://www.nktechnologies.com/pdfs/ATCR_data_sheet.pdf

Blijj said:

But all those inputs into 22.5mm???

Click to expand...

Actually, each input would go into its own 22.5mm signal conditioner and then to the multiplexer listed above. I'll look into everything else you've said, but this is for an industrial cabinet so I'm really looking for premade devices. Im not even sure if my company would let me fabricate something like this.