Zero Point Adjustment - Endress+Hauser PROline prosonic flow 90 Operating Instructions Manual

PROline Prosonic Flow 90
"
Endress+Hauser
6.2.4

Zero point adjustment

Consequently, zero point adjustment is generally not necessary.
Experience shows that the zero point adjustment is advisable only in special cases:
x To achieve highest measuring accuracy also with very small flow rates.
x Under extreme process or operating conditions (e.g. very high process temperatures
or very high viscosity fluids).
Preconditions for a zero point adjustment
Note the following before you perform a zero point adjustment:
x A zero point adjustment can be performed only with fluids that contain no gas or solid
contents.
x Zero point adjustment is performed with the pipe completely filled and at zero flow
(v = 0 m/s). This can be achieved, for example, with shut-off valves upstream and/or
downstream of the measuring range or by using existing valves and gates (Fig. 46).
– Standard operation o valves 1 and 2 open
– Zero point adjustment with pump pressure o valve 1 open / valve 2 closed
– Zero point adjustment without pump pressure o valve 1 closed / valve 2 open
Caution!
x If the fluid is very difficult to measure (e.g. containing entrained solids or gas) it may
prove impossible to obtain a stable zero point despite repeated zero point adjust-
ments. In instances of this nature, please contact your E+H service center.
x You can view the currently valid zero point value using the "ZERO POINT" function
(see the "Description of Device Functions" manual).
Fig. 46: Zero point adjustment and shut-off valves
2
1
6 Commissioning
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