The maximum span is 8000-400 or 7600 mm, so the absolute error at different levels is:
Level Distance Absolute Error (1% of set span)
0 % (empty) 1% of 7600 mm 76 mm
25 % 1% of 7600 mm 76 mm
50 % 1% of 7600 mm 76 mm
75 % 1% of 7600 mm 76 mm
100 % (full) 1% of 7600 mm 76 mm
A percentage of empty distance statement describes a parameter that is in error by a constant percentage of the farthest measurement distance in the span. In the measurement of 100-1100 mm high vessel (100% level located 100 mm below the sensor) measured with an accuracy of 1 percent of empty distance, the empty distance is 1100 mm, so the absolute error can be calculated as:
Level Distance Absolute Error (1% of empty distance)
0 % (empty) 1% of 1100 mm 11 mm
25 % 1% of 1100 mm 11 mm
50 % 1% of 1100 mm 11 mm
75 % 1% of 1100 mm 11 mm
100 % (full) 1% of 1100 mm 11 mm
The percentage of maximum sensor distance statement is similar to an absolute (fixed) distance error statement in that its absolute error is constant. However, the error is related to the maximum distance that can be measured by the sensor. For example, the stated accuracy of a level measurement system in a 1000 mm high vessel (100% level located 100 mm below the sensor) might be +/-1 percent of maximum sensor distance of 8000 mm. The absolute error at different levels is:
Level Distance Absolute Error (1% of maximum distance)
0 % (empty) 1% of 8000 mm 80 mm
25 % 1% of 8000 mm 80 mm
50 % 1% of 8000 mm 80 mm
75 % 1% of 8000 mm 80 mm
100 % (full) 1% of 8000 mm 80 mm
Excerpted from The Consumer Guide to Non-Contact Level Gauges.