VEGA MINITRAC 31 Profibus PA - Manual (Page 33)

33
6 Set up with the display and adjustment module
MINITRAC 31 • Profibus PA
43836-EN-131119
The natural radiation on earth influences the accuracy of the meas-
urement.
With this menu item the natural background radiation can be faded
out.
For this purpose, the MINITRAC 31 measures the natural background
radiation and sets the pulse rate to zero.
In the future, the pulse rate from this background radiation will be
automatically deducted from the total pulse rate. This means: only
the component of the pulse rate originating from the source will be
displayed.
The source container must be closed for this setting.
In this menu item you can select the units of the process value and
the temperature.
In this menu item you can enter the measuring range (min. and max.
process value) of the sensor.
These settings influence the current output of the sensor.
Enter in the menu window "Max. process value" the max. level (full),
for example in "m". This corresponds to an output current of 20 mA.
Enter in the menu window "Min. process value" the min. level (empty),
for example in "m". This corresponds to an output current of 4 mA.
In this menu item you can carry out the adjustment of the sensor.
Due to the measuring principle, there is no linear relationship between
pulse rate and level. Hence, this adjustment (i.e. linearisation) must in
any case be carried out.
Note:
If you cannot fill the vessel with the original medium, it is also possible
to carry out the adjustment with water.
Prerequisites:
Radiation is switched on - Source container is set to "ON"
The vessel is either completely filled (100 %) or completely emptied
(0 %).
Depending on the fact if the vessel is filled or emptied, you can car-
ried out first the full or the empty adjustment. The MINITRAC 31 sorts
the points automatically according to their level.
Select "Show table" to display and edit the linearization points.
Select "Linearization - New" to enter the first point.
Select "Determine count rate" to enter the first point.
The determination of the actual count rate lasts 2 minutes. After the
count rate has been determined, you can accept the value (ct/s).
Enter now the corresponding level (m).
By doing so, you assign a respective level to the actual count rate.
Setup - Background
radiation
Setup - Units
Setup - Adjustment
Setup - Linearization