Campbell CR800 Series, Руководство оператора

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Section 10. Troubleshooting
467
10.5.3.1.1 Voltage Measurements
The CR800 has the following user-selectable voltage ranges: ±5000 mV, ±2500
mV, ±250 mV, and ±25 mV. Input signals that exceed these ranges result in an
over-range indicated by a NAN for the measured result. With auto range to
automatically select the best input range, a
NAN
indicates that either one or both
of the two measurements in the auto-range sequence over ranged. See
Troubleshooting — Auto Self-Calibration Errors .
A voltage input not connected to a sensor is floating and the resulting measured
voltage often remains near the voltage of the previous measurement. Floating
measurements tend to wander in time, and can mimic a valid measurement. The
C (open input detect/common-mode null) range-code option is used to force a
NAN result for open (floating) inputs.
10.5.3.1.2 SDI-12 Measurements
NAN is loaded into the first SDI12Recorder() variable under the following
conditions:
•
CR800 is busy with terminal commands
• When the command is an invalid command.
• When the sensor aborts with CR LF and there is no data.
•
When 0 is returned for the number of values in response to the M! or C!
command.
10.5.3.2 Floating-Point Math, NAN, and ±INF
Related Topics:
• Floating-Point Arithmetic
(p. 160)
• Floating-Point Math, NAN, and ±INF
(p. 467)
•
TABLE: Data Types in Variable Memory
(p. 127)
Table Math Expressions and CRBasic Results
(p. 468)
lists math expressions, their
CRBasic form, and IEEE floating point-math result loaded into variables declared
as FLOAT or STRING.
10.5.3.3 Data Types, NAN, and ±INF
NAN and ±INF are presented differently depending on the declared-variable data
type. Further, they are recorded differently depending on the final-memory data
type chosen compounded with the declared-variable data type used as the source
( TABLE: Variable and FS Data Types with NAN and ±INF
(p. 468)
). For example,
INF , in a variable declared As LONG , is represented by the integer –
2147483648 . When that variable is used as the source, the final-memory word
when sampled as UINT2 is stored as 0.