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98640A Analog Input Interface
An outline of the procedure follows. The sequence shown is not the only one possible.
1. Measure offset
Read the reference channel at the same gain you will use to read the
input channel. This reading is the Crude_Offset.
2. Apply offset
A. Read the input channel you are interested in. This is Uncalibrated
_Input_Reading.
B. Subtract the Crude_Offset from Uncalibrated_Input_Reading.
The difference is Roughly _Corrected_Reading.
Since Crude_Offset and Uncalibrated_Input_Reading are real numbers, Roughly_Corrected
_Reading may be less than, equal to, or greater than Uncalibrated _Input_Reading.
GAIN
UNCALIBRATED*
QUICK
CALIBRATION
(WORST CASE)**
DETAILED
CALIBRATION
(WORST CASE)
MEASUREMENT
LIBRARY
CALIBRATION
(WORST CASE)***
Table 4-1. Comparison of offset ranges
1
OFFSET RANGE
1
1
--------------------------------------------------------I
1
1
8
64
512
1
--------------------------------------------------------I
(PERCENT OF FULL SCALE)
1
1
±O.32
±O.39
±O.96
±5.6
1
--------------------------------------------------------I
1
I
±o.60
±o.60
±o.60
±o.60
I
±O.lO
±O.10
±O.12
±O.15
±O.07
±O.07
±O.lO
±O.12
*This is not a specification.
It is a theoretical worst case.
**The offset's range and symmetry is polarity dependent.
See table
4-2.
***See Table
1-1
where these values are expressed as voltages.
4-6
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