Hello,
I will try to explain your project:
To read a flow of LPG you must install a Gas-Flow-Sensor at LPG station, it is called as "SLAVE". The slave can more one not only one slave.
And the reader is called as "MASTER". The master is only one, because you only need to read a flow rate of LPG from all slave.
To connect all slave to master, you must use a RS-485 for multi node not RS-232 because it is one master and one slave only. The drive of RS-485 please try a compenent MAX-485, look at
www.maxim-ic.com.
SLAVE Hardware requirement:
- Gas-flow-sensor.
- ADC try MAX-186 look at
www.maxim-ic.com search this component.
- RS-485 driver MAX-485 (simplex)
- ATMEL AT89C51 or other
MASTER Hardware requirement:
PC-Used:
- MAX-485 and L232 (RS-232) to convert RS-232 level to RS-485 level.
- Software mybe Visual BASIC or Visual C
The Slaves must have different address to indentification station number.
Please try to build a schematic.
Thank's