Endress+Hauser Proline Promag 300 - Page 111

Proline Promag 300 Modbus RS485 Description of device parameters
Endress+Hauser 111
Additional information Description
The process variable that is assigned to the current output via the Assign curr.
parameter (→  106) is displayed below the parameter.
"Forward flow" option
The current output signal is proportional to the process variable assigned. The measuring
range is defined by the values that are assigned to the 0/4 mA and 20 mA current value.
The flow components outside the scaled measuring range are taken into account for signal
output as follows:
• Both values are defined such that they are not equal to zero flow e.g.:
– 0/4 mA current value = –5 m
3
/h
– 20 mA current value = 10 m
3
/h
• If the effective flow exceeds or falls below this measuring range, the diagnostic message
S441 Curr.output 1 to n is displayed.
"Forward/Reverse" option
Q
20
0
I [mA]
4
3 1
2
0
A0013758
I Current
Q Flow
1 Value assigned to the 0/4 mA current
2 Forward flow
3 Reverse flow
• The current output signal is independent of the direction of flow (absolute amount of the
measured variable). The values for the 0/4 mA value parameter (→  108) and 20 mA
value parameter (→  109) must have the same sign.
• The value for the 20 mA value parameter (→  109) (e.g. reverse flow) corresponds to
the mirrored value for the 20 mA value parameter (→  109) (e.g. forward flow).
"Rev. flow comp." option
The Rev. flow comp. option is primarily used to compensate for abrupt reverse flow which
can occur in connection with positive displacement pumps as a result of wear or high
viscosity. The reverse flows are recorded in a buffer and balanced against forward flow the
next time flow is in the forward direction.
If buffering cannot be processed within approx. 60 s, the diagnostic message
S441 Curr.output 1 to n is displayed.
Flow values can aggregate in the buffer in the event of prolonged and unwanted fluid
reverse flow. However, these flows are not taken into consideration by the current output
configuration, i.e. the reverse flow is not compensated.
If this option is set, the measuring device does not attenuate the flow signal. The flow
signal is not attenuated.
Examples of how the current output behaves
Example 1
Defined measuring range: lower range value and upper range value with the same sign