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CY8CKIT-025 PSoC® Precision Analog Temperature Sensor Expansion Board Kit Guide, Doc. # 001-65791 Rev. *J 36
Example Projects
7. Press CapSense button
P0_5
to scroll down the menu and
P0_6
to scroll up the menu.
8. Use SW1 to proceed through calibration steps; see RTD Calibration on page 47 .
9. Use SW2 to return to the previous step during calibration.
5.2.2.3 Testing the Project
For best results when testing temperature measurements, ensure that you have good thermal con-
tact between the sensor and your reference thermometer. Also, make sure there is minimal air flow,
which can result in temperature gradient. Sample test results are given in the following sections.
5.2.2.4 Expected Performance and Test Results
This section explains the expected resolution and accuracy of the temperature displayed by all the
sensors.
5.2.2.4.1 Accuracy
The accuracy of the temperature displayed depends on the sensor and the signal chain.
Sensor
Each sensor has a tolerance, which is available in the datasheet provided by the sensor manufac-
turer. The tolerance indicates the error due to replacement of one sensor with another of the same
part number. The tolerance of each onboard sensor is listed in
Table 5-1 . These numbers are from
the respective sensor datasheets.
For diode, the ideality factor is the source of its tolerance. This number is generally not mentioned in
the diode datasheet and must be determined experimentally. Diode ideality factor generally lies
between 1 and 1.01. An ideality factor difference of 0.004 (using 1.008 instead of 1.004) causes an
error of around 2 °C. See
AN60590 - PSoC 3 and PSoC 5LP - Temperature Measurement with a
Diode for more details on these calculations.
Signal Chain
Signal chain error includes the errors due to the ADC, IDAC, the calibration (reference) resistors and
the measurement method. The resources used differ from sensor to sensor.
The main sources of ADC error are its offset, gain error, and INL. Of these, the offset error is can-
celled in all cases by correlated double sampling. ADC gain error is eliminated by using a precision
reference resistor in thermistor and RTD.
Table 5-1. Temperature Sensor Tolerances
Sensor Tolerance Standard
Maximum Tolerance
Error at 25 °C
Maximum Tolerance
Error at 100°C
Thermocouple
5SRTC-GG-K-20-36
ASTM special limits of error
1.1 °C or 0.4%, whichever is
higher
± 1.1 °C ± 1.1 °C
Thermistor
NCP18XH103F03RB 1% at 25 °C
1% B-value tolerance
± 0.4 °C ± 2 °C
RTD
PTS080501B100RP100 IEC Class B RTD
(0.30 + 0.005T) °C
± 0.43 °C ± 0.8 °C
Diode – – –
IC – ± 0.5 °C ± 0.5 °C