Endress+Hauser Prosonic S FMU90 PROFIBUS DP - Advanced Settings

Commissioning Prosonic S FMU90 PROFIBUS DP
60 Endress+Hauser
9.4 Advanced settings
9.4.1 Configuration of backwater or dirt detection
General principles
FMU90
1
2
Q
h
1
h
2
A0035517
 49 Backwater detection with two ultrasonic sensors
1 Upstream sensor
h
1
Upstream level
2 Downstream sensor
h
2
Downstream level
Flow measurement can be compromised by backwater on the downstream side or by dirt
within the flume. These problems can be detected by the backwater and dirt detection
function. Two sensors are required for backwater and dirt detection - one on the upstream
side and the other on the downstream side. The device evaluates the ratio of the
downstream level h
2
to the upstream level h
1
.
Position of the downstream sensor
Mount the sensor on the downstream side at a sufficient distance from the flume
discharge point. Select the measuring point in such a way that the surface of the water is
calm and the level is not influenced by the flume.
Backwater detection
The device detects the buildup of backwater when the ratio h
2
/h
1
exceeds a critical value
(typically 0.8 for Venturi flumes). It then continuously reduces the displayed flow to 0. In
addition, a backwater alarm relay can be configured that signals an alert when backwater
builds up.
Dirt detection
Dirt within the flume is detected if the ratio h
2
/h
1
drops below a critical value (typically
0.1). A dirt alarm relay can be configured that signals an alert when there is dirt in the
flume.
Setup sequence
1. Navigate to Flow → Flow 1 +backwater → Flow → Basic setup
2. Configure the upstream sensor (flow measurement).
3. Navigate to Flow → Flow 1 +backwater → Backwater → Basic setup