Campbell CR850 - NAN and ±INF; Floating-Point Math, NAN, and ±INF; Measurements; Measurements and NAN

Section 10. Troubleshooting
408
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results can be difficult due to the multitasking nature of the logger, but it can be a
useful tool for fine tuning a program.
10.3.4 NAN and ±INF
NAN (not-a-number) and ±INF (infinite) are data words indicating an exceptional
occurrence in datalogger function or processing. NAN is a constant that can be
used in expressions as shown in CRBasic example Using NAN in Expressions
(p.
408).
. NAN can also be used in conjunction with the disable variable (DisableVar)
in output processing (data storage) instructions as shown in CRBasic example
Using NAN to Filter Data
(p. 410).
10.3.4.1 Measurements and NAN
A NAN indicates an invalid measurement.
10.3.4.1.1 Voltage Measurements
The CR800 has the following user-selectable voltage ranges: ±5000 mV, ±2500
mV, ±250 mV, ±25 mV, ±7.5 mV, ±2.5 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. 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 can be used to force
a NAN result for open (floating) inputs.
10.3.4.1.2 SDI-12 Measurements
NAN is loaded into the first SDI12Recorder() variable under these conditions:
• When busy with terminal commands.
• When the command is an invalid command.
• When the sensor aborts with CR LF and there is no data.
CRBasic EXAMPLE. Using NAN in Expressions
CRBasicExample67. UsingNANinExpressions
If WindDir = NAN Then
WDFlag = False
Else
WDFlag = True
EndIf
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10.3.4.2 Floating-Point Math, NAN, and ±INF
Table Math Expressions and CRBasic Results (p. 409) lists math expressions, their
CRBasic form, and IEEE floating point-math result loaded into variables declared
as FLOAT or STRING.