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ST100A Series Flow Meter OPERATION

Fluid Components International LLC 77

Modbus Operation

The ST100A Series offers Modbus as one of its digital communication protocol, but unlike the other digital communication protocols

Modbus only offers set up and configuration for the totalizer variable. Refer to Modbus Connections on page 29 for Modbus wiring info.

The ST100A Series Modbus physical layer uses the flow meter’s asynchronous RS-485 serial port. There is no high speed Modbus over

Ethernet. The ST100A Series offers the two basic traditional transmission serial interface modes: RTU and ASCII message coding.

The ST100A Series offers the process variable parameters (value) in floating point form, which are organized as single or double precision

floating point registers. These registers are the 4000 and the 5000 group registers, both of which are accessed using Modbus 03 and 04

function codes. Refer to Table 21, page 79, for an overview of the registers.

The S

Setting the ST100A Series for Modbus Operation

T100A Series Configuration Software application is used to select the instrument’s digital communication protocol.

Using the supplied USB cable, connect the instrument’s USB port to a USB port on the PC running the configurator software.

Launch the ST100A Series Configurator (with the PC already connected to the instrument). Select Configuration branch from the menu

tree on the window’s left side. Observe that the Output tab is selected. In the window’s Digital Output Selection field, check whether or not

Modbus is shown for Digital Bus. If not, use the Digital Bus pulldown menu to select Modbus. Then click Send to Device to program the

ST100A Series (enter “2772” user password).

Figure 57 – ST100A Series Configuration Software Output Tab with Modbus Selected

Click the Modbus tab and

configure the serial interface parameters (Node ID, Mode, Baud, Data Bits, Parity, and Stop Bits) as required for

your application. Then click Send to Device to program the ST100A Series (enter “2772” user password). Refer to the ST100A Series

Configuration Software manual 06EN003481 for details on configuring the digital bus and using the software.

FCI ST100A Series User Manual

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