How does the fluid conductivity measurement?

Each manufacturer specifies a minimum conductivity depends on the technology and dimensions of each model. The changes in the conductivity of the fluid that are above this threshold have no effect on the measurement. The problems arise with low conductivity fluids because they induce low voltages on the electrodes. The lower the conductivity, the harder it is to distinguish between measuring tension and stress caused by noise. The problem arises at the lower end of the field measurement values. At that point, the signals can lose all its significance, because it is impossible to distinguish signal from noise.

How do temperature, pressure and fluid viscosity measurement?

Only the sensor materials of construction and lining impose limitations to the range of applicability in terms of pressure and temperature. The effects of pressure, temperature and viscosity on the measurements themselves are negligible.

How do the turbulence and vortex measurement?

Magnetic flowmeters are affected by turbulence sometimes originating, for example, the flow control valves, pumps, elbows 90 degrees. Most of flowmeters are affected by the formation of vortices, but the magnetic assimilate it better because the extension of the magnetic field tends to moderate the effects on all three dimensions. Thus, long straight stretches upstream reduce the influence of those elements. At this point it is important to have the manufacturer's advice, because each model requires straight sections of different lengths. It is desirable that the velocity profiles at the point of measurement are symmetrical as possible.

How does the measurement eíhecho Failure to observe the lengths of the input and output sections recommended?

In these circumstances you can have a measurement error of more than 1% or higher. If, however, respect the lengths of the input and output sections that the manufacturer recommends, the velocity profile does not affect the measurement. In any case, a distorted velocity profile for this reason less effect on a magnetic flowmeter to a turbine, vortex, ultrasonic, or PD type.

What advantages and the disadvantages of capacitive measuring electrodes?

The magnetic flowmeter signal detection capacitive electrodes to measure very low conductivity fluids. Furthermore, they are less affected by sediments of insulating materials that land on the pipe wall measuring devices whose electrodes are immersed in the fluid.

Moreover, the voltage signal provided by these electrodes is significantly lower. This can cause irregularities in the measured values. Another disadvantage is that this method of measurement is affected by temperature changes. The accuracy of the measurement with capacitive signal detection is not as high as in the case of sensors whose electrodes, submerged.

How do they affect the measurement of conductive material deposition inside the pipe?

The stools inside the measuring tube should be avoided where possible. The deposition of conductive materials have two effects that occur simultaneously. The first is that the lower bowel section flow, which increases fluid velocity and you get a flow value overestimated. Second, the deposited conductive materials reduce the sensitivity of the electrodes because they cause low voltage signals underestimate the actual flow. In fortuitous cases, these two effects cancel each other can reach and give an accurate reading. However, these cases are rare and do not usually show.

In the worst cases, these deposits of short-circuit conductor may tar-induced measuring voltage to the electrodes of land. The solution is to clean the measuring tube or install a sensor with an ECC circuit constantly keep the electrodes clean. The ECC circuit periodically applies a voltage of 8 to 10 volts between the electrode and the reference measurement that helps the detachment of the deposited conductive materials. However, only thus can remove thin coatings of conductive materials. Should therefore be maintained and preventive cleaning cycle appropriate to each specific application.

How do they affect the measurement of nonconductive materials deposition at the electrodes?

The non-conductive material (eg fat dairy products) that are deposited on the electrodes form an insulating layer that causes measurement errors. And, as already described, can change the section of stream flow. Consequently, the reading rate can fluctuate to a value lower than the real or even fall to zero. To avoid these effects, you can apply some of these measures:

- Clean the measuring tube regularly.

- Increase the speed of the fluid.

- Use replaceable measuring electrode (no need to terminate the process). This measure is only possible with certain nominal diameters.

- Use measurement electrodes of special shape, for example, electrode-tipped "bullet head" in the case of oil-film deposition.

How does the measurement the presence of gas bubbles or solid?

The presence of gases or solids on the surface of the electrodes causes a number of electrochemical effects. These effects affect the induced voltage directly registered by the measuring device.

- If solid particles flow near an electrode, can be drawn between short-range electrochemical interactions that distort the measurement.

- Gas bubbles on the surface of the electrodes act as an insulator. Injections of gas in the fluid cause measurement errors that are proportional to the amount of gas contained in the fluid. It is therefore advisable to avoid gas leaks in the fluid.

When mixed with liquid gas, it is better to make the measurement in a vertical pipe. Good results were obtained for two-phase flow with magnetic flow meters, provided that the gas content does not exceed 5% by volume.

- The rapid changes in pH or conductivity in chemically inhomogeneous can also cause problems.

The transmitter detects all these effects as an increase in noise (some algorithms magnetic flowmeters include reducing noise level). Some magnetic solids, for example in the mining industry, producing spurious fields can distort the powerful magnetic field to prevent any measurement point. The shape and length of the solid particles in the fluid are also qualitative factors that may distort the magnetic field and affect the reproducibility of the measurement. For certain applications with fluid problem, a solution should be worked properly between the manufacturer and user. In these cases it is more important when detailed knowledge of the application and the measurement principle.

Is it possible to effectively measure flows of liquids with solid content?

The theory states that any driver can be pumped fluid can be measured. It may be necessary some special sensors, but in general will be able to measure fluids with suspended particles, cellulose pulp or sludge with a satisfactory degree of reproducibility. Note, however, that this will require special software to eliminate noise, and a strong magnetic field, yet able to react quickly when necessary. The final result of measurements in these conditions is a better relationship between the interfering signals (noise) and the measured signal itself. Magnetic flowmeters have been used with a high level of performance to measure the following fluids:

- In the mining industry muddy fluids containing solids up to 75 or 80% by weight.

- In the paper industry: pulp fibers of different lengths, to solid content of about 20% by volume.

- In the water management industry: muddy sediments with low water content of up to 25% by volume.

Is it possible to measure flow of abrasive fluids?

Yes these cases is important to select a sensor coating material appropriate, particularly if the fluid is highly abrasive. Brush-type electrodes tend to wear less and are often the first choice in the applications of this nature.

How does it affect the measurement a partially full pipe?

If the pipe is empty, the measurement electrodes are not immersed in the fluid and the measurement is not possible. If the pipe is partially empty but full enough so that the measuring electrodes are in contact with the fluid, the measurement error is proportional to air content. Although models have been developed for special applications of this type are still in an experimental phase.

Fig: Installation of a magnetic flow meter inverted siphon tube ensures that the measurement is always completely full. The opening for cleaning (below) is used to remove solids that may be trapped in the trap and for regular cleaning operations.

Excellent results have been obtained by installing the sensor in a vertical pipe, since in these cases, the risk that the pipe is partially empty is relatively low. It is always advisable not to install the sensor at the highest point of a pipe (at the risk of accumulation of gases) or upstream of a free download (because the fluid could be turbulent). In sloping pipe, the flowmeter should be installed on an inverted siphon to ensure that the fluid always fills the measuring tube (Fig. above). The sensor can be equipped with an electrode empty pipe detection, which automatically detects when the pipes are only partially filled and triggers an alarm.

How does the "removal of residual flow" measurement?

The purpose of the role of residual flow suppression is to prevent the flow record a minimum flow in the lower end of the field measured values, caused for example by a flucuación a column of fluid in a steady state. If you reach the point of removal of residual flow, the transmitter software eliminates all signs of flow (flow = zero).

How much maintenance does a magnetic flow meter?

In general, magnetic flowmeters are low maintenance devices. However, to clean the measuring tube must be removed depositions and other debris that may have mechanical influences. The flowmeters distribution companies offer a major recalibration of the device or appropriate diagnostic tools to detect these early influences.

How important is a good grounding in making measurements?

When measuring voltage too low, you need to download for a suitable and effective method possible pipe spurious currents that may arise. This is achieved with the help of ground rings. Ensure good grounding of the fluid is therefore essential. Under normal circumstances, this requirement is satisfied if the pipe itself is metal.