Endress+Hauser Micropilot FMR56 - Page 145

Micropilot FMR50/FMR51/FMR52/FMR53/FMR54/FMR56/FMR57 FOUNDATION Fieldbus The "Expert" menu
Endress+Hauser 145
Application example: Foam detection
Preconditions
• The process runs at a fixed level (in the example: 80 %)
• If foam occurs during the operation, the vessel should automatically be sprinkled with
water from the top or an antifoam agent should be added to dissolve the foam.
Reaction of the radar signal in the case of foam formation
The echo amplitude decreases in the case of foam formation. This can be used by the
Advanced Diagnostics to detect the foam. The foam detection, however, should only be
active as long as the level is between 75 % and 85 %.
85%
75%
A A
A0019640
 21 Decrease of the amplitude in case of foam formation
A Amplitude threshold for foam detection
Step 1: Determination of the amplitude threshold
Observe the echo amplitude while the process is running at the given level (in the example:
80 %) and determine the lower limit for the amplitude (in the example: 10 dB).
The Maximum value 1/2(→  153) and Minimum value 1/2(→  153) parameters
can be used for this.
Step 2: Configuration of the level monitoring
In order to ensure that the level actually is in the vicinity of the given value: Configure
Advanced Diagnostics 1 as follows:
• Assign diagnostic signal 1 = Level linearized
• Check mode 1 = Out of range
Out of range checks whether the level is outside a defined range. As long as this is the
case, the block outputs "0" (INACTIVE). If the level gets into the defined range, the block
outputs "1" (ACTIVE).
• Upper limit 1 = 85 %
• Lower limit 1 = 75 %
With this setting, the output of Advanced Diagnostics 1 assumes the following value:
• 0 (INACTIVE) - if the level is outside the defined range (out of range).
• 1 (ACTIVE) - if the level is within the defined range. The foam detection should only be
active in this case.