7.4.1
Adjust the general threshold
If necessary, the general threshold value can be increased if a disturbance echo is
interpreted as the product surface. Alternatively, a lower threshold may be required to
handle weak surface echoes (e.g. due to excessive foaming or turbulence).
Prerequisites
The general threshold is set at factory for optimum performance and should not normally
need an adjustment.
Before changing the factory default value, study the position and amplitude of the
different echo peaks.
Procedure
1. Under
Menu
, select
Parameter
→
Advanced Setup
.
2. In the
General Threshold
box, enter the desired value.
3. Select
Write to device
.
Related information
Analyze the echo peaks
General threshold
7.4.2
Change the upper null zone
The Upper Null Zone defines a zone close to the transmitter where echoes are ignored.
This zone can be extended to block out disturbing echoes at the top of the tank.
Prerequisites
Note
Make sure the Upper Range Value (100%/20 mA) value is below the Upper Null Zone.
Measurements are not performed within the Upper Null Zone.
Procedure
1. Identify desired Upper Null Zone by analyzing the echo peaks.
a) Under
Menu
, select
Diagnosis
→
Echo Peaks
.
b) View the echo peaks to find out if there are disturbing echoes close to tank
top.
2. Set the desired Upper Null Zone value.
a) Under
Menu
, select
Parameter
→
Geometry
→
Advanced
.
b) Enter the desired Upper Null Zone value.
c) Select
Write to device
.
Service and troubleshooting
Reference Manual
May 2021
00809-0200-4480
60
Rosemount 1408A Level and Flow Transmitter
