Application Notes
R01AN4788EJ0110 Rev.1.10 Page 1 of 20
July 20.20
RX23E-A Group
Temperature Measurement Examples Using Resistance Temperature Detectors
Summary
This document describes temperature measurement examples with resistance temperature detectors (RTD),
using RX23E-A.
RX23E-A contains an analog front-end (AFE) and a 24-bit Δ-Σ A/D converter (DSAD). Using the
programmable gain instrumentation amplifier (PGA), excitation current source (IEXC), etc., high-precision
A/D conversion is performed on the output of the resistance temperature detector to calculate the
temperature.
Temperature was measured with RTD, using Renesas Solution Starter Kit for RX23E-A and sample program
included in this document. Error of temperature measurement result with 3-wire RTD is shown in below
figure.
Measuring range:
-40°C ~ 150°C
Board temperature:
-40°C
、
room temperature (about 25°C) , 85°C
Effective resolution:
21.3bit
（
121.2nVrms: 1.26m°C equivalent
）
Noise free resolution:
18.7bit
（
738.2nV: 7.67m°C equivalent
）
Target Device
RX23E-A
-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
-50 -25 0 25 50 75 100 125 150
Error [°C]
Temperature [°C]
85℃
Room Temp
-40℃
Sensor Error
RX23E-A Group Temperature Measurement Examples Using Resistance Temperature Detectors
R01AN4788EJ0110 Rev.1.10 Page 2 of 27
July 20.20
Contents
1. Overview ................................................................................................................................. 3
2. Related Documents ................................................................................................................. 3
3. Environment for Operation Confirmation .................................................................................. 3
4. Temperature Measurement Systems ....................................................................................... 4
4.1 Resistance Temperature Detectors (RTDs) ............................................................................................ 5
4.2 Temperature Calculation Procedure ....................................................................................................... 7
4.3 Other Functions ....................................................................................................................................... 8
4.3.1 Calibration ............................................................................................................................................. 8
4.3.2 3-Wire RTD Excitation Current Chopping ............................................................................................. 8
4.3.3 Linkage with the PC Tool Program........................................................................................................ 8
5. Sample Program ...................................................................................................................... 9
5.1 Overview of Operation ............................................................................................................................. 9
5.2 Peripheral Functions and Pins Used ..................................................................................................... 10
5.2.1 AFE and DSAD0.................................................................................................................................. 11
5.2.2 SCI1, DMAC0, DMAC3, and CMT0 .................................................................................................... 12
5.2.3 Port PH2 .............................................................................................................................................. 13
5.3 Communication Control ......................................................................................................................... 14
5.4 Program Configuration .......................................................................................................................... 16
5.4.1 File Configuration ................................................................................................................................ 16
5.4.2 Macro Definitions ................................................................................................................................. 17
5.4.3 Structure .............................................................................................................................................. 17
5.4.4 Functions ............................................................................................................................................. 18
6. Importing a Project................................................................................................................. 21
6.1 Importing a Project into e
2
studio .......................................................................................................... 21
6.2 Importing a Project into CS+ ................................................................................................................. 22
7. Measurement Results with Sample Program ......................................................................... 23
7.1 Memory Usage and Number of Execution Cycle .................................................................................. 23
7.1.1 Build Conditions................................................................................................................................... 23
7.1.2 Memory Usage .................................................................................................................................... 23
7.1.3 The number of Execution Cycle .......................................................................................................... 23
7.2 Temperature Measurement ................................................................................................................... 24
7.2.1 Measurement Condition ...................................................................................................................... 24
7.2.2 Calibration ........................................................................................................................................... 24
7.2.3 Measurement Results ......................................................................................................................... 25
7.2.3.1 4-wire RTD ........................................................................................................................................ 25
7.2.3.2 3-wire RTD ........................................................................................................................................ 26
Revision History ............................................................................................................................ 27