Over Range; Simple Sample - HP 98640A Installation And Reference Manual

Table 4-2. Judging polarity effects.
EFFECTS OF POLARITY ON OFFSET RANGE
(apply to Quick Calibration)
98640A Analog Input Interface
IF INPUT
1
AND REFERENCE
1
OFFSET CORRECTED TO WITHIN
POLARITY IS:
1
POLARITY IS:
1
n PERCENT OF FULL SCALE:
--------·-----------1-----------------------1------------------------------
+
1
+
1
±O.15
-------_·_----------1-----------------------1------------------------------
+
1 1
-0.15 to +0.60
-------_·_----------1-----------------------1------------------------------
1
+
1
-0.60 to +0.15
-------_·_----------1-----------------------1------------------------------
1 1 ±O.15
If you chose to ignore the polarity of the offset and the input, you must regard the offset as corrected
to within ±O.60% of full scale. If you take into account polarity, you will be able to judge the correc-
tion of the offset more closely. See tables 4-1 and 4- 2.
To convert to a voltage, multiply Roughly _Corrected_Reading by the Isb value for the gain used to
read the input channel. The sign indicates the polarity of the voltage.
OVERRANGES
Normal modle
If all 12 data bits (bit 0 to bit 11) are set to 1, a normal mode overrange has occurred. You may be
able to avoid this problem by taking subsequent readings at a lower gain.
Common mode
If the overrange bit (bit 13) is set to 0, a common mode overrange has occurred. Lowering the gain
may also solve this problem.
SIMPLE SAMPLE
The following example shows a subroutine for taking a single analog reading. It is an assembly lan-
guage routine callable from Pascal in the HP 9000 Series 200 Pascal language system environment.
4-7