Campbell Scientific CR6 CR6 Measurement and Control System - Page 478
Voltage Measurements, 5.4.1.2, SDI-12 Measurements
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Section 10. Troubleshooting WDFlag = False Else WDFlag = True EndIf 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. 480). 10.5.4.1 Measurements and NAN A NAN indicates an invalid measurement. 10.5.4.1.1 Voltage Measurements The CR6 has the following user-selectable voltage ranges: ±5000 mV, ±1000 mV, and ±200 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 the section Calibration Errors (p. 477). 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. 10.5.4.1.2 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. • When 0 is returned for the number of values in response to the M! or C! command 10.5.4.2 Floating-Point Math, NAN, and ±INF Table Math Expressions and CRBasic Results (p. 479) lists math expressions, their CRBasic form, and IEEE floating point-math result loaded into variables declared as FLOAT or STRING. 10.5.4.3 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. 479) ). 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. 478