This examination is to find out if the minimum length of straight pipe, suggested by one manufacturer of an 100 mm's electromagnetic flowmeter, is sufficient. The meter was calibrated before the test with several types of bends, plates and cones in front of and behind the meter. During this calibration a tube bundle straightener (ISO 5167) was fixed 9D in front of the meter and a straight pipe for 5D behind it. This K-factor is used as a reference when we specify the deviation with different applications. From the results you will notice that a straight pipe of 3 to 5D, suggested by the manufacturer, isn't enough. These numbers are not to be used as corrections with similar applications. They could be different for other manufacturers. The flow standard used is a ball prover with a nominal volume of 3500 l.