## Additional Information

Example Calculation:

The following is an example of calculating

*Absolute Accuracy* for an SCXI-1102 system measuring a type J thermocouple at 100 °C. First we will assume that the ambient temperature falls within the 15-35 °C range, then we will calculate the accuracy accounting for temperature drift.

A type J thermocouple at 100 °C generates 5.268 mV (this value is from a standard type J conversion table or formula). We will assume in our temperature task, we are using a range of ±100 mV or applying a gain of 100. The remaining necessary components to Absolute Accuracy can be found in the

SCXI-1102/B/C User Manual.

**Variable** | **Value** | **Value Used in Equation** |

*Input Voltage* | 5.268 mV | 0.005268 V |

*Percent of Reading MAX (gain error)* | 0.02% | 0.0002 |

*Offset* | 15 µV | 0.000015 V |

*System Noise (Avg)* | 5 µV | 0.000005 V |

*Absolute Accuracy* = ±[(

*Input Voltage* x

*% of Reading*) +

*Offset* +

*System Noise* +

*Temperature Drift*]

*Absolute Accuracy* = ±[(0.005268 x 0.0002) + 0.000015 + 0.000005] V = ±21.05 µV

A voltage of ±21.05 µV translates to about ± 0.5°C using a standard formula for J type thermocouples. Thus our range would be 99.5-100.5 °C.

If the ambient temperature may fluctuate outside of the 15-35 °C range, we then need to take into account temperature drift. If we take the same example above in an ambient temperature of 45 °C we would calculate the

*Absolute Accuracy* as follows:

**Variable** | **Value ** | **Value Used in Equation** |

*Input Voltage* | 5.268 mV | 0.005268 V |

*Temperature Difference* | 45-35 °C | 10 °C |

*Percent of Reading/**°C* | 0.00002 (1/°C) | 0.00002 (1/°C) |

*Offset/°C* | 1.5 µV | 0.0000015 (V/°C) |

*Temperature Drift* = ±[(

*Input Voltage* x

*% of Reading/°C*)+

*Offset/°C*] x

*Temperature Difference*

Temperature Drift = ±[(0.005268 x 0.00002)+ 0.0000015](V/°C) x 10°C = ±16.05 µV

*Absolute Accuracy *= ±(21.05 + 16.05)µV = ±37.10 µV

A voltage of ±37.10 µV translates to about ±0.8 °C using a standard formula for J type thermocouples. Thus our range would be 99.2-100.8 °C.