S.4.2.4 the offset shift (os) definition, 1 example 1 (for negative offsets), 4 the offset shift (os) definition - 9 – Fluke 900 User Manual
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FLUKE 900 SERVICE MANUAL
Maintenance
additional capacitor
fiQ. 1
S.4.2.4 The Offset Shift (OS) Definition
For any line that needs to be corrected the necessary shift should be determined. The
general rule is: if there are excessive negative offsets a resistor will be put on this line, and
if there are excessive positive offsets a capacitor will be used.
OS should be calculated for the calibration data block that has the biggest offset for a
given channel.
NOTE: Limits table cannot be used for OS calculation.
The OS calculating procedure is explained with the two following examples.
5.4.2.4.1
Example 1 (for negative offsets)
Assume line 3 has the biggest offset in 80 ns block.
..80 ns..
pin# U-H D-H U-L D-L
3
-3
-4
-5
-7
The biggest offset is D-L. It has to be moved up 3 units to make it -4 and therefore
within spec. AU other offsets wiU be moved by ¿he same amoimt, therefore U-H will
be 0. The best situation, however, is when there is a safety margin at the top and the
bottom. In this case all offsets should be moved up by 5 units. Then after correction it
would be:
... 80 ns..
pin# U-H D-H U-L D-L
3
-^2 +1
0
-2
5-9