Flow Meter Tech Bulletin: The Bi-directional Sensor -Flow Meter

Tech Bulletin: The Bi-Directional Sensor

Engineer Venko Gyokov checks the circuitry for the bi-directional sensor

First I'd like to cover the basics of how our standard and bi-directional sensors work and how they differ. The standard sensor detects just the rotation of the rotor, not the direction of rotation. So the sensor generates the same pulses no matter what the direction of rotation is. In the situation where there is flow in both directions, the indicated flow total would be the sum of both flows (Forward Flow + Reverse Flow).

The bi-directional sensor is really two detectors; one for each direction of flow. Each detector generates pulses for only one direction of rotation and ignores rotation in the opposite direction. Using this sensor, with flow in both directions you would have a separate flow total for each direction (Forward Flow total & Reverse Flow total). Please refer to drawing below.

Typical bi-directional installation

Some typical applications:

You have the situation where you are using a common inlet and outlet, (flow in both directions) and you want to proportionately add chemical, but only in one direction while filling a tank. You would use just the inflow signal, to control your metering pump, much the same as you would if you had flow in only one direction.

In the building energy management field, you would see bi-directional flow in chilled water loops. Depending on the system demands, flow could be in a forward or reverse direction. The bi-directional flow sensor tells the energy management computer how much chilled water is flowing, and which way.

Zoya Zinchuk examines a sheet of production boards

Bi-directional sensor before potting

The SeaMetrics bi-directional sensor is compatible with all our electronics with the exception of the FT415 unit. This provides a great deal of flexibility in usage; you can use this with one or two of the FT420's. If your needs are for a 4 to 20 mA output, you can use our A055W, also with one or two units depending on the application.