Adjustment; Zero Point Adjustment - Endress+Hauser Proline Promass 84 MODBUS RS485 Operating Instructions Manual

Commissioning
"
64
6.4

Adjustment

6.4.1

Zero point adjustment

All Promass measuring devices are calibrated with state-of-the-art technology.
The zero point obtained in this way is printed on the nameplate.
Calibration takes place under reference operating conditions → ä 118.
Consequently, the zero point adjustment is generally not necessary for Promass!
Experience shows that the zero point adjustment is advisable only in special cases:
• To achieve highest measuring accuracy also at very small flow rates.
• 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:
• A zero point adjustment can be performed only with fluids that contain no gas or solid contents.
• 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 shutoff valves upstream and/or downstream
of the sensor or by using existing valves and gates.
– 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
Fig. 44: Zero point adjustment and shutoff valves
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 adjustments. In instances of
this nature, please contact your Endress+Hauser representative.
• You can view the currently valid zero point value using the "ZEROPOINT" function (see the
"Description of Device Functions" manual).
Proline Promass 84 MODBUS RS485
2
1
a0003601
Endress+Hauser