6 Commissioning Promass 40
28 Endress+Hauser
6.2.2 Zero point adjustment
The Promass 40 E is calibrated with state-of-the-art technology. The zero point obtained
in this way is printed on the nameplate. Calibration takes place under reference operat-
ing conditions (see Page 53). Consequently, zero point adjustment is generally not nec-
essary.
Experience shows that the zero point adjustment is advisable only in special cases:
• with very small flow rates
• under extreme process or operating conditions (e.g. very high process pressures or
very high viscosity fluids).
Preconditions for a zero point adjustment
Note the following before you perform a zero point adjustment:
• A zero point adjustment can be performed only with fluids that contain no gas or solid
contents.
• A zero point adjustment is performed with the measuring tubes 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 sensor or by using existing valves and gates
(Fig. 17):
– Normal operation
→ valves 1 and 2 open
– Zero point adjustment with pump pressure
→ valve 1 open / valve 2 closed
– Zero point adjustment without pump pressure
→ valve 1 closed / valve 2 open
Caution:
• 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.
• You can view the currently valid zero point value using the “ZERO POINT” function
(see the “Description of Device Functions” manual).
Fig. 17: Zero point adjustment and shut-off valves
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