Several common problems with flowmeters

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　　Flow measurement is an important basis for corporate financial accounting. Accurate and reliable flow measurement is a prerequisite for ensuring the normal operation of enterprises, and it is one of the key means to achieve optimal economic benefits. 　　The calibration of the zero point of a flow measurement system: There is no difference between calibrating the zero point of a flow measurement system on-site and doing so in a laboratory; in both cases, the flow rate passing through the flow meter is set to zero, and then the reading on the flow meter is taken. It’s just that the on-site conditions are not as ideal as those in a laboratory, with many unfavorable factors. 　　Experienced engineering supervisors or inspectors always check the zero reading of the flow meter when inspecting and verifying it before it is put into use, as this calibration is the easiest to carry out and also the most important. 　　During verification, the flow meter must not generate values out of nowhere, nor should it indicate negative values. The following points should be noted when zeroing. 　　1. Ensure that the flow rate of the fluid passing through the flow meter is indeed zero. This is the basis for zeroing the flow meter. There are not many cut-off valves that can remain leak-free after being closed and used on-site for a period of time. Therefore, when calibrating to zero, this point needs to be confirmed in order to avoid backfiring. 　　2. The measurement channel of the flow meter must be filled with the medium to be measured. This is particularly important for electromagnetic flowmeters. This is because most electromagnetic flowmeters indicate a full-scale value when the measuring tube is empty; this occurs since an open circuit exists between the electrodes when the tube is empty, causing the reading to exceed the full scale. 　　3. Small-signal cutoff problem. For flowmeters that output analog signals, slight drift in the analog circuitry inevitably leads to a minor offset in the zero point. It is usually resolved by using the small-signal cutoff method, but this method also has drawbacks, as the low-amplitude signals below the cutoff point are also removed, so the cutoff point cannot be set too high. With flow meters becoming generally programmable, the cut-off point can be set arbitrarily as needed, providing an effective solution to this problem. It should be noted, however, that some transmitters (such as differential pressure transmitters) experience zero-point drift due to a certain inclination in their installation location or as a result of mechanical stress; this issue cannot be resolved by using signal attenuation methods, and must be addressed through zero-point calibration.