Common problems in the vortex street flowmeter calibration solution
Vortex flowmeter is mainly used for industrial piping medium fluid flow measurement, such as gas, liquid, steam and other media. Is characterized by small pressure loss, wide range, high precision, working condition of the measurement volume flow is almost not affected by the fluid density, the influence of the parameters such as pressure, temperature, viscosity. Have no moving parts, thus high reliability, small amount of maintenance. The instrument can encroach on long-term stability. Vortex street flowmeter using piezoelectric stress sensor, can work in - 20 ℃ ~ 250 ℃ temperature range. There are standard signal simulation and digital pulse signal output, easy with the computer and digital systems, is a more advanced, the ideal flow meter.
1, after electrify, when no flow through the header has signal output
(1) the table body, the system is not bad grounding or block.
(2) not with flowmeter with special signal lines.
(3) near a large motor or strong electromagnetic interference sources.
Verification of no flow but often see the pipe flowmeter output is a slight change of interference signals or a fixed, in the laboratory environment, caused by grounding more likely to appear this kind of problem, also found that some colleagues work split type instrument appears more caused by not using a special signal lines. So should try to make sure before test case and good grounding system, and use a dedicated line or meet the requirements of the alternative signal lines, colleagues around to ensure that no strong electric field disturbance or by isolation measures or anti-interference techniques to avoid impact.
2, no 4 ma ~ 2 ma current output
(1) meter connection errors.
(2) current amplification output circuit damage.
(3) the output mode set error.
Such problems first determine according to the instruction manual correct connection, electronic display menu, and check the header is properly set the output mode. Sure there are no errors in other ways, change the current output circuit board or to replace the damaged components.
3, flow but no signal output
(1) set the flow is too small, weak signal cannot be detected.
(2) small flow to remove excessive or meter automatic filter Settings.
(3) the amplification output circuit damage.
(4) detector probe damage or detector and converter cable is broken.
Verification has been encountered in the pipe flow, without any single flowmeter signal output. First check whether traffic electromagnetic set according to the flow meter manual range setting, traffic does not exceed the instructions indicate the reference flow on the lower limit. Check whether the flow meter is small flow to remove excessive or filter parameter setting is not appropriate. With conditions by changing the circuit board check without output is caused by damage of circuit board, after the completion of the above check may be due to the detector probe whether the damage or the transformation circuit connection is broken cause problems.
4, the output signal is not stable
(1) check whether there is foreign body inside the pipe or flow meter.
(2) look for leak test line and verification system.
(3) flow meter grounded.
(4) the meter circuit boards set is not appropriate, the sensitivity setting inappropriate cause much plan, meter pulse leakage phenomenon.
Verification in the output model is not stable, may lead to repeated verification structure is bad. Because offices shall use the standard devices are in strict accordance with the requirements of the construction of the, there is no lack of straight pipe before and after or strong vibration problems. In ready to test, so you just need to check verification pipeline internal flow vortex occurred and whether to have influence on the flow field of a foreign body, colleagues check grounding the entire verification system leakage, flow meter, the output sensitivity of flow stability, especially the small flow itself is not reasonable, can also lead to repeat.
5, flow lose present value and the actual flow error is bigger
(1) when installation to strictly ensure the concentricity.
(2) set the flow range does not accord with the meter itself.
(3) the out-of-tolerance meter itself.
Flowmeter calibration error if found, the first thing to check there is no a large deviation, flowmeter calibration of concentricity influence on the results, at the same time to ensure that the test program set flow range and flow meter itself flow range is consistent, avoid the error due to more than measuring range is too large. More cases may be due to the instrument coefficient of input is not correct, or changes coefficient error, can be adjusted by the instrument coefficient to ensure accurate measurement.
Through the above measures, can solve the problem of verification common, but flowmeter calibration and test conditions with different devices, different circumstances, the production of the new problem, need more practice and summary, better to complete the verification work.