Replacement for Emerson Model 3201 HIU and 3402 AIM

Hello All.

The sketch below provides information about my tank gauging system. Does any one know a device or combination of devices that can replace the HIU and AIM? They are now unsupportable. I am open to a new communication protocol and possibly changing the field instruments for compatibility.

1. HIU - Hydrostatic Interface Unit, Emerson Model 3201

•Powers and communicates with the field transmitters over HART using single twisted pair cable.

•Computes tank level.

•Communicates data to AIM over Modbus Communication and Power (MCAP) using single twisted pair cable.

2. TT, PT - temperature transmitter and pressure transmitter respectively.

•Provides tank temperature and pressure to the HIU.

•Standard transmitters, not in conventional 4-20mA loop. Daisy-chained on HART cable.

3. AIM - Application Interface Module, Emerson Model 3402

•Powers and communicates with the HIU over MCAP using single twisted pair cable. One AIM can power several HIU's.

•Converts MCAP to RS485 and RS232 standard MODBUS.

Constraints - No laying of new instrument / power / home-run cables. Field is Class 1 Div 2 hazardous location. Distance from field to control room is about 500meters.

Thanks.

Apologies if sketch is not sufficiently legible, it's the best I could get after several attempts to paste on the site.