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SmartAir lite Modbus RS 485
How to interface (SmartAir lite) controller to DCS.

We have (SmartAir lite) controller to manage the compressors working. We have more than one compressors with own Delcos. the communication with DCS will be via (SmartAir lite) controller. DCS programmer ask me to let the (SmartAir lite) controller working as Modbus RS 485 Slave with following specification:

1. Slave address - 3.
2. Parity - none.
3. Badrate - 9600.

and ask me to provide Available Data and their Address details. For me it is the first time to work with (SmartAir lite).

What your DCS guy is asking for a very logical - the DCS is the Modbus (or OPC client) master which means the field device, the SmartAir Lite needs to be a Modbus slave. Modbus slave's each have a unique slave node address (1 through 247). The baud rate and parity need to match the DCS serial port's parity and baud rate, presumably on a multidrop RS-485 network.

The communications documentation lists the Modbus register addresses for specific tag or data items, and usually covers the hardware connection, the RS-485 network connections and serial settings.

However, a Google search for "SmartAir Lite" brings up a sales brochure for a SmartAir Lite, but no communications documentation manual. Gardner Denver's Compair.com site is a sales-only site that posts no manuals that I can find, so information on your SmartAir Lite is scarce, to say the least.

The sales brochure states:
"Options:
Network gateways for modbus master, profibus and devicenet"

It isn't clear whether the reference to an optional Modbus Master Network gateway means
- the SmartLir Lite can only be a Modbus master (with the gateway option), or

- the SmartAirLite is a Modbus slave that talks to an optional, vendor supported Modbus master gateway

You'll have to post a link to the SmartAir Lite's Modbus communications manual if you want help from someone who knows Modbus but does not know SmartAir Lite. Or maybe you'll get lucky and someone who's used SmartAir Lite, has its documentation will reply here.