Fluke 900 - Manual (Page 90)

Maintenance FLUKE 900 SERVICE MANUAL
S.4.2.6 Calibration Procedure
As a preliminary condition, the HS Board must pass all selftests with the exception of
tests 28 through 40 which are related to the calibration.
Unless otherwise specified all points in the following procedure should be performed in
the order stated. First load the calibration data as follows:
- Go to engineering menu: start from the main screen and press ( cntr ] and the point
between l next I and [ test ).
- Go to calibration mode: press (ED(calib).
- Press lE3(f_mask) and wait until the loading of data is done.
- Print calibration data to a printer connected to the serial port by pressing ©(print).
The data may also be displayed on the LCD display by pressing ©(show) .
NOTE: Do not touch HS Board during loading of calibration data.
5.4.2.6.1 Offsets Block
AU pins that have offset (one or more) bigger then 4 (positive or negative) should be
corrected following the steps:
A - Define OS and component for all pins that need correction (see Section S.4.2.4).
B - Place aU components determined in step A on the board on related lines and then
load calibration data again (see Section S.4.2.6).
C - Press ©(show) to display the data. Using "SHIFT” and "arrow down" keys, check
the data (see Section S.4.2.2); if there are stiU lines that need correction, do it the
same way as described in step A, with one difference: the offset shift should be
selected to be the minimum required with no safety margin.
If after these steps the board is still not calibrated go to Section S.4.2.6.2
5.4.2.6.2 Limits Block
This block is related to the 74ALS09 chips that are located in FI, F2 etc. areas. There
is only one such chip in each area.
Only two columns are relevant: U-L and D-L. The conditions they have to fulfill are
as follows:
- each offset should be equal to -2,-1,0,1,2
- the difference between the lowest and the highest offsets should be 2 or less.
Example:
pin# U-L D-L
5 - 1 2