Campbell-scientific CR1000 Measurement and Control System Uživatelský manuál stáhnout pdf (Strana 308)

100

101

Section 8. Operation

308



Error Calculations with Input Reversal = True

µVerror=gainterm+offsetterm

=(830.7µV*0.12%)+(1.5*0.67µV+1.0µV)

=0.997µV+2.01µV

=3.01µV(=0.071°C)

Error Calculations with Input Reversal = False

µVError=gainterm+offsetterm

=(830.7µV*0.12%)+(3*0.

67µV+2.0µV)

=0.997µV+4.01µV

=5.01µV(=0.12°C)

Input Error Examples: Type K Thermocouple @ 1300°C

Error in the temperature due to inaccuracy in the measurement of the

thermocouple voltage increases at temperature extremes, particularly when the

temperature and thermocouple type require using the ±200|250 mV range. For

example, assume type K (chromel-alumel) thermocouples are used to measure

temperatures around 1300°C.

These examples demonstrate that at temperature extremes, input offset error is

much less than input gain error because the use of a larger input range is required.

Conditions

CR1000moduletemperature,‐25to50°C

Temperature=1300°C

Referencetemperature=25°C

DeltaT(temperaturedifference)=1275°C

Thermocoupleoutputmultiplierat1300°C=34.9µV°C

‐1



Thermocoupleoutput=1275°C*34.9µV°C

‐1

=44500µV

Inputrange=±250mV

Error Calculations with Input Reversal = True

µVerror=gainterm+offsetterm

=(44500µV*0.12%)+(1.5*66.7µV+1.0µV)

=53.4µV+101.0µV

=154µV(=4.41°C)

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