Omega Flow Meter


Omega Ultrasonic Flow Meter from their site: The TFX-500w transit time ultrasonic flow meter measures volumetric flow of clean water in pipes 2 in. or smaller. By clamping on the outside of the pipe, the ultrasonic meter installs without cutting or tapping the pipe..


Install the flow meter according to the User Manual listed in the Manuals & Downloads section of the Flow Meter page.

Pay close attention to the section on Acoustic Coupling Grease, as flow readings require this.

Electrical Wiring

The Omega Flow Meter can supply a 4-20mA analog signal to the controller and/or an RS-485 Modbus digital signal.

  • 24v external DC power supply shown as green / green stripe in the example diagram. This must be supplied externally.

  • 4-20mA Signal If you wish to read input as an analog 4-20mA signal, see the small shunt and +/- wires to send to an Opto22 controller channel configured for 4-20mA input.

  • Modbus RS-485 Signal If you wish to read input as a digital Modbus signal, this requires a +/- wire pair from the RS-485 terminal to the ModLink LX-2 module. See the Modbus Wiring section for more details.

Modbus RS-485 Wiring

The +/- wires from the RS-485 terminal in the Omega sensor are sent to the A/B inputs of the ModLINK LX-2 adapter.

The RS-485 negative (-) terminal goes to the A port of the LX-2, and the RS-485 positive (+) terminal goes to the B port of the LX-2.

Multiple Omega flow meters can be wired to a single ModLINK LX-2 by daisy chaining the flow meter RS-485 (+) and (-) RS-485 terminals among multiple flow meters.

The LX-2 is then wired to the HX8 8-port hub using Cat-5 cable and the adapter supplied with the LX-2.

We recommend adding dielectric grease to all Cat-5 connections to prevent corrosion in humid environments.

Omega Configuration

Once plumbing and electrical wiring is complete, power up the unit and navigate the System Setup menu for your installation. Pay close attention to the following settings based on the type of input signal chosen:

For 4-20mA Signal

Setup -> Input/Output -> Current Output -> Output Source -> Flow RateSetup -> Input/Output -> Current Output -> Range -> 4-20 mASetup -> Input/Output -> Current Output -> Min Value -> +000000.00Setup -> Input/Output -> Current Output -> Max Value -> +000030.00 (set to max GPM)

For RS-485 Modbus Signal

Setup -> Communications -> Network Type -> Modbus RTUSetup -> Communications -> Settings -> Address -> 030 (enter a network-wide unique address)Setup -> Communications -> Settings -> Baud Rate -> 19200Setup -> Communications -> Settings -> Parity -> NoneSetup -> Communications -> Settings -> Stop Bit -> 1 Stop BitSetup -> Communications -> Settings -> Resistor -> Disabled (Enabled if end unit in a chain)Setup -> Communications -> Settings -> Word Order -> Big EndianSetup -> Communications -> Settings -> Timeout -> 03500

Adding the Card to the HMI

To add a card, press the button on the upper right of the Devices screen on the HMI. This opens a panel to select the new card type.

Choose the Omega Ultrasonic Flow Meter card type, and a new card of that type is added to the device card palette.

Card Configuration


The Units section allows selection of the units of measure you are collecting. Each Omega supported unit of measure is available.

Input Channel

The input channel section lets you choose between the two different types of input - analog 4-20mA or digital RS-485 Modbus.

4-20mA Configuration - When 4-20mA input is selected, a section is added to select the input channel for this flow meter from the Opto22, and a section for calibration.

Analog input must be calibrated by entering the low and high readings from the Opto22 card at the low and high flow rates.

Modbus Configuration - When Modbus input is selected, a section is added to enter the unique modbus Unit number specified for this flow meter, and how often to read the meter.

Reading every 2 seconds is a good starting point, and this can be extended to ease the CPU burden on systems with many flow meters on a single controller.

Using the Card

The front of the card shows the current water flow as reported by the meter, and the units of measure selected in the configuration.