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The Main Reasons of the Error Produced By the Mag Meter II

(4) The problems caused by electrode and the improper choice of grounding ring material quality

The mag meter whose breakdown is brought about by the mismatching between material quality and measured medium has electrode and grounding ring with the parts which have contact with the medium. What the mismatching results in are not only the corrosive problems and surface effect of the electrode. The surface effect contains:

①Chemical reaction( the surface will produce passive film, and etc.)

②Electrochemistry and polarization phenomenon( generating electric potential)

③Catalytic action( the surface of electrode produces inhalator, and etc.)

The grounding ring also has these reactions but its influential degree is much smaller.

(5) The problem caused by the liquid conductivity which surpasses the permissible range.

The liquid conductivity will be likely to have the shaking phenomenon when it is nearly reaching to the lower limit value. Because the specification of an instrument made by the manufacturer has stipulated that the lower limit value is the lowest value which can be measured in a status with various better-using conditions. While the actual conditions can not be so ideal that it meets with distilled water that is low degree and deionized water, resulting in its conductivity is near to the lower limit value 5 which is set by the specifications of mag meter. Consequently, when it is used, its output is shaking. It is generally acknowledged that the lower limit value of conductivity which can be measured stably is above 1 to 2’s order of magnitude. We can read some relevant manual to know something about liquid conductivity, and a lack of ready—made data can be measured by means of taking conductivity meter to test its samples. But sometimes when it is recognized to be useful for taking the samples from the pipeline to have a test in the laboratory, while the reality is that, the mag meter is not able to work. This is because the liquid is different from the one in the pipeline when testing the conductivity. For example, the liquid has absorbed the CO2 or NO in the atmosphere to produce carbonic acid or nitric acid, leading the increase of conductivity. As for the noisy liquid produced by the liquid which contains granule or fiber, it is better to choose the method which can enhance pumping frequency for improving the shaking of output. Some rates can readjust the DN300 mag meter of IFM3080F type, measure the slurry with a corrugated board whose concentration is 3.5% and display the swaying measurement of instantaneous delivery which is measured by different pumping frequency on the spot. When the rate is rather low, which is 50/32Hz, the swaying measurement can be up to 10.7%; when the rate is raised to 50/2Hz, the swaying measurement is down to 1.9%. That means it has an obvious effect.

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