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7-5
7.5 Measurement near the bottom surface of the tank
When the liquid to be measured has low permittivity, such as oil, microwaves pass through the liquid
and there is a very intense reflection echo of the bottom surface. If the fluid level of such a liquid
decreases, a surface echo cannot be distinguished from a bottom echo. Therefore, bottom echoes must
be set to be ignored. For liquids with low permittivity, set the setting parameter "Bottom Recognition" to
"ON". For liquids with high permittivity, such as water, there is no reflection echo from the bottom,
because few microwaves pass through the liquid. Therefore, no considerations need to be made
regarding the bottom echo, and thus, the setting parameter "Bottom Recognition" can be set to "OFF".
7.6 Calibrating analog current output
If you are calibrating the analog current output using the LCD and operation keys, first set the "Fixed
Current Output" parameter to current value 4 mA / 20 mA. After setting this, measure the value of the
actual output current. If the output current value is different from the setting value, set the measured
current value to "4-mA calibration" / "20-mA calibration". After setting this, the output is calibrated.
If you are calibrating the analog current output using the configuration software, directly select "4-mA
calibration" / "20-mA calibration", and then follow the instructions in the window.
7.7 Calibrating measurement values
If the measured value has shifted, it is possible to perform the corresponding offset adjustment. To
perform offset adjustment, set the adjustment value in the "Zero-point Calibration" parameter. Also, in
situations such as when the device was slanted when it was installed, the corresponding span
calibration must be performed. To perform span calibration, set the adjustment value in the "Span
Calibration" parameter. Normally, this value is set to "1". For example, if the device was slanted when it
was installed, the actual distance is longer. By setting a value smaller than "1", that can be corrected.
7.8 Averaging time and Median filter
The averaging time make average for the measurement data group within the set time moving average
time.
In the case of waving small liquid level change, it is possible to set a large average time is valid. If
the large average time set, follow-up of the liquid level will be bad in the case of fast liquid level change.
Median filter is the ability to remove the minimum value and maximum value from measurement data
group when performing a moving average.
The averaging time set 8[sec] and the median filter set 2[sec],
In the case of, Measurement data (8) - Removal data (2) = Valid data (6), it makes an average of 6 data
processing.
Please set the valid data of greater than 1, refer to
6.6.1 Measure support .