Density Meter LB 444 SECTION 2. SYSTEM DESCRIPTION
18
Rapid switch-over:
The function "Rapid switch-over" (=1/10 of the defined time constant) is needed
to adjust the output signal quickly to the new value in the presence of sudden
density changes. This function is enabled and disabled via <
ON
> and <
OFF
>.
Sigma defines a range (window) which the display change has to exceed before
the selected time constant automatically switches over to a value that is smaller
by a factor of 10 (max. to 0.8 sec).
When using the rapid switch-over function, enter "
4
" or "
5
" as Sigma value to
make sure that a switch-over of the time constant is not triggered merely by sta-
tistical variations or minor density changes. We recommend the determination of
optimum entry value during routine operation (see also section 6.4 Automatic
Measuring Time Switchover).
Radiation interference:
The function "Radiation interference" is needed only when unforeseeable influ-
ences due to interfering radiation are to be expected. This function is enabled
and disabled via <
ON
> and <
OFF
>. Sigma defines a limit value which the dis-
play change has to exceed before the measurement is aborted (see also section
6.3 Interference Radiation Detection).
Enabling the radiation interference de-
tection disables the rapid switchover function.
Maximum Rate:
If the countrate supplied by the detector exceeds the entered value, the meas-
urement is stopped automatically. The output current signal is held at the last
value. The error message "Measurement halted" appears on the display. If the
countrate drops below the entered value again, the measurement continues
automatically.
The entered values are permanently corrected during decay compensation.
The functions „Maximum Rate“ and „Minimum Rate“ can be used to “freeze” the
measured value in case of problems (e.g. empty measuring path, empty con-
tainer, increased radiation due to weld seam testing, etc) and to avoid long re-
sponse times of the control devices. Select the input values such that that they
will not be reached during regular operation.
Minimum Rate:
If the countrate supplied by the detector falls below the entered value, the
measurement is automatically halted. If this function is not important for your
operation, you can disable it by entering a pulse rate of „0“.
Current Input:
Temperature compensation via current input. Select the current input range 0-20
mA or 4-20 mA. For mass flow measurements the range defined here is used in
the menu sk2 Volume Flow.
Temp. Input 0/4mA: 20mA:
These entries are required only for temperature compensation via current input.
Enter the upper and lower temperature values for 0/4mA or 20mA.
Product Selection [extern/intern]
Define if the product is to be selected via the evaluation unit (= internal) or via
digital inputs (= external, 18a and 18c, 20a and 20c).
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