2 Features and Functions
System Overview
Figure 2-1 System overview of U2802A with DAQ
The U2802A is essentially an amplifier module with a built- in temperature sensor (thermistor). In thermocouple mode, the U2802A input channel is used to amplify a differential voltage signal from a thermocouple (or any low voltage signal source in the range of ±100 mV) by 100 times. The signal is then output as an analog voltage in the ±10 V range into the DAQ for conversion to a digital voltage reading.
The built- in thermistor in the U2802A can be read from Channel AI148 of the U2300A series DAQ. The conversion from voltage to temperature for this thermistor reading is done automatically by the AMM software. This temperature reading will subsequently be used as the Cold Junction Compensation (CJC) reference temperature.
With the correct voltage reading from the thermocouple and the CJC temperature, the AMM software will then proceed to convert the thermocouple voltage reading into a temperature reading, based on the NIST ITS- 90 Thermocouple Database. This reading is then corrected for both gain and offset errors due to the U2802A amplifiers using the calibration constants stored in the U2802A EEPROM, which are read by the PC via the DAQ's digital I/O lines.
The U2802A also has a built- in zeroing function, which allows users to zero out the entire system's offset error, thus increasing the overall accuracy of the system.
28 | Agilent U2802A |
