In many industrial applications, it is essential to understand how to calculate flow rates from the output current of flow meters. This is particularly important for accurate monitoring and control of fluid flow in various systems. The output current, typically in the range of 4-20mA, correlates with the flow rate, and this relationship can be used to derive the flow value.
Here are two examples to illustrate the calculation process.
1. Calculation Method for Differential Pressure Flow Meters
Consider a differential pressure flow meter with an output current of 4-20mA, corresponding to a flow range of 0-160m³/h. If the output current is 8mA, what is the flow rate?
The flow rate (Q) is related to the differential pressure (△P) by a constant (K), and the relationship can be expressed as:
Q = K × △P
Since the differential pressure has already been converted into an output current (I) by the transmitter, the relationship between the flow meter’s flow rate and current can be represented as:
At an output current of 8mA, the flow rate is 80m³/h.
2. Calculation Method for Linear Output Flow Meters
Now, consider a vortex flow meter with an output of 4-20mA, corresponding to a flow range of 0-20,000kg/h. If the output current is 16mA, what is the flow rate?
In this case, the flow rate is directly proportional to the output current, following a linear relationship:
At an output current of 16mA, the flow rate is 15,000kg/h.
Conclusion
By understanding the relationship between output current and flow rate, operators can accurately calculate the flow of fluids in various systems. Different flow meters may have different output characteristics, such as linear or nonlinear relationships, which must be accounted for when performing these calculations.