What Is a Digital Flow Meter?
A digital flow meter is a flowmeter that transmits the results of measurements made by a flow meter as a digital signal. A flow meter is an instrument that measures the mass and volume per unit time of fluids such as gas, liquid, and steam.
The flow value measured by a flow meter is constantly changing as the fluid is flowing. This meter converts the analog value of this continuous measured value into a digital value and transmits it. Some flow meters come with an indicator and transmitter (digital signal transmitter), while others have the indicator and transmitter separately.
Uses of Digital Flow Meters
Uses of digital flow meters include not only visual confirmation of the instantaneous flow value measured by the flow meter, but also transmission of the flow value as data to various control devices for flow control using flow control valves in the control system, and monitoring consumption by accumulating the output totalized flow data.
In addition, the upper and lower flow limits can be monitored, alarms can be issued and displayed, and the control system can close off the fluid flow.
Therefore, digital flow meters are widely used in various plants and manufacturing sites where fluids are used, and where flow data is used for automation and control.
Principle of Digital Flow Meters
The principle of digital flow meters, as an example, is that in a turbine flow meter, an impeller (rotor) installed in a pipeline is rotated by the fluid, which in turn rotates a magnet attached to the impeller. This magnet rotates in proportion to the flow velocity and the rotation speed is detected by a pickup coil (a non-contact reed switch element inside the body) and converted into a pulse string signal suitable for remote transmission by a converter for output.
This pulse signal is output each time and sampled (measured time and measured value are extracted as data) as digital values at regular time intervals (e.g., from 1 to 100 times/second). The sampled digital data is transmitted and output together with the measurement time information. The digital data is subjected to moving average processing and integration processing before being output.
In recent times, some of them are equipped with a microprocessor, have judgment and communication functions as well as detection, storage, and calculation, and come with an intelligent type transmitter that is compatible with field bus (a digital communication system that allows bi-directional signal exchange).
The use of such digital transmitters makes it possible to control fluids based on accurate numerical values and information, thereby expanding the possibilities for process control.