
29
NT UF 811 CP GB (e) / June 2015
4.1 Composition of a measuring point
Apart from the electronic converter (the unit), a measuring point includes the following components:
1 to 2 pairs of probes
1 to 4 special cables for the probes (provided by Ultraflux)
4.2 Choosing the measurement location
It is essential to follow the instructions given in our document “Ultrasonic
transit time flowmeter
". As a
reminder, the main precautions to be taken are as follows:
4.2.1 Straight lengths to be used
1) Monochord measurement
Using a monochord measurement implies that the speed profile at the measuring point is symmetrical
relative to the axis of the pipe, and is fully developed and stable.
The following three conditions are not fulfilled in an area of disturbed flow, for example, at the outlet from
an elbow or downstream from a regulating valve:
The speed profile is stable but not symmetric relative to the axis of the pipe.
The symmetry of the speed profile varies relative to the pipe axis but is nether stable nor
fully developed.
This is why probes need to be placed on a straight section of pipe sufficiently far upstream or downstream
of a hydraulic disturbance (narrowing or widening of the pipe, elbow, pump, etc.).
The following values show, for liquids, the minimum distances (L) to comply with before and after a
disturbance depending on the internal diameter of the pipe (D) for the errors induced by these disturbances
to be less than ± 1 %.
Comment
:
The values shown must
be multiplied by 2.5 for
gases.
Содержание Uf 811
Страница 4: ...4 NT UF 811 CP GB e June 2015 CHAPTER 1 OVERVIEW...
Страница 11: ...11 NT UF 811 CP GB e June 2015 CHAPTER 2 SAFETY INSTRUCTIONS...
Страница 14: ...14 NT UF 811 CP GB e June 2015 CHAPTER 3 INSTALLATION AND WIRING...
Страница 28: ...28 NT UF 811 CP GB e June 2015 CHAPTER 4 INSTALLING A MEASURING POINT...
Страница 30: ...30 NT UF 811 CP GB e June 2015...
Страница 38: ...38 NT UF 811 CP GB e June 2015 CHAPTER 5 USING AND CONFIGURING THE Uf 811...
Страница 65: ...65 NT UF 811 CP GB e June 2015 CHAPTER 6 FUNCTION ENGINE...
Страница 67: ...67 NT UF 811 CP GB e June 2015 CHAPTER 7 PC SOFTWARE...
Страница 81: ...81 NT UF 811 CP GB e June 2015 Appendix I Characteristic echo signals...
Страница 84: ...84 NT UF 811 CP GB e June 2015 Appendix II Speed of sound in water...