Environmental Engineering Reference
In-Depth Information
Voltage
Electromagnet
Flow
figure 2.28 Magnetic flowmeter.
•
Wide range of sizes
•
Bidirectional flow measurement
•
Negligible effect from variations in density, viscosity, pressure, and
temperature
•
Can be used for wastewater
•
No moving parts
Disadvantages include:
• Metered liquid must be conductive (but you would not use this type
of meter on clean fluids anyway).
•
They are bulky and expensive in smaller sizes, and they may require
periodic calibration to correct drifting of the signal.
The combination of a magnetic flow meter and transmitter is con-
sidered to be a system. A typical system, illustrated in Figure 2.29,
includes a transmitter mounted remote from the magnetic flow meter,
although some systems are available with transmitters mounted integral
to the magnetic flow meter. Each device is individually calibrated during
the manufacturing process, and the accuracy statement of the magnetic
flow meter includes both pieces of equipment. One is not sold or used
without the other. It is also interesting to note that, since 1983, almost
every manufacturer has offered the microprocessor-based transmitter.
Meter
Signal
conditioner
mA DC
V AC
figure 2.29 Magnetic flowmeter system.
