CN-0300 Datasheet, PDF (6/7 Pages) Analog Devices – Complete Closed-Loop Precision Analog Microcontroller Thermocouple

Circuit Note
A Wavetek 4808 multifunction calibrator wasusedto fully evaluate
the error, asshown in Figure 13. In this mode, the thermocouple
was replacedwith the calibratorasthe voltage source.To evaluate
the entire range of a Type T thermocouple, the calibratorwas
used to set the equivalent thermocouple voltage at 52 points
between −200°C to +350°C for the negative and positive ranges
of the T-type thermocouple (see the ISE, Inc., ITS-90 Table for
Type T Thermocouple). Figure 8 shows the test results.
When doing performance checks and using the CN0300 circuit
for normal operation,please ensure the J-Link OB emulator is
unplugged from the EVAL-CN0300-EB1Z board—only use the
J-Link OB when programming, calibrating and debugging the
EVAL-CN0300-EB1Z board.
THERMOCOUPLE
JUNCTION
J2
EVAL-CN0300-EB1Z
SEE TEXT
WAVETEK 4808
MULTIFUNCTION
CALIBRATOR
AIN7/VBIAS
USB
CABLE
PC
Figure 13. Test Setup Used to Calibrate and Test the Circuit Over Full
Thermocouple Output Voltage Range
RTD Measurement Test
To evaluate the RTD circuit and linearization source code, the
RTD on the board was replaced with an accurate,adjustable
resistance source. The instrument used was the 1433-Z decade
resistor. The RTD valuesare from 90 Ω to 140 Ω, whichrepresents
an RTD temperature range of −25°C to +114°C.
The testsetup circuit formeasuringthe RTD is shown in Figure 14,
and the error resultsfor the RTD testsare shown in Figure 15.
AVDD IOVDD
0.1µF
0.1µF
1433-Z
DECADE
RESISTOR
10Ω
0.01µF
10Ω
0.01µF
R_REF
5.6kΩ
0.1%
AVDD IOVDD
AIN5/IEXC
AIN0
AIN1
ADuCM360
VREF+
VREF–
Figure 14. Test Setup for Measuring RTD Error
CN-0300
0
–0.01
–0.02
–0.03
–0.04
–0.05
–0.06
–0.07
–0.08
–0.09
–0.10
–25 –5
15
35
55
75
TEMPERATURE (°C)
95 115
Figure 15. Error in °C of RTD Measurement Using Piecewise Linearization
Code and ADC0 Measurements
Current Measurement Tests
When operating normally, the entire circuit consumes2.25 mA
typically. When held in a reset state, the entire circuit consumes
less than 600 µA.
When doing performance checks and using the CN0300 circuit
for normal operation,please ensure the J-Link OB emulator is
unplugged from the EVAL-CN0300-EB1Z board—only use the
J-Link OB when programming, calibrating and debugging the
EVAL-CN0300-EB1Z board.
For more details on the current consumption figures for the
ADuCM360, see Application Note AN-1111.
Rev. A | Page 6 of 7