CY8CKIT-025 PSoC® Precision Analog Temperature Sensor Expansion Board Kit Guide, Doc. # 001-65791 Rev. *J
49
Example Projects
5.2.3.3.6
Diode Calibration
Diode temperature measurement follows the equation:
Equation 9
Here
is the ideality factor of the diode, varied from diode to diode. The temperature variation result-
ing from the ideality factor variation can be calibrated out. As equation 9 shows, variation in
results
in a scale error. Performing a scale correction eliminates this error. The procedure to perform scale
calibration is as follows:
1. Scroll down to the
Calibrate Diode1
(ninth) or
Calibrate Diode2
(tenth) item in the menu using
CapSense buttons. Proceed through the calibration steps using mechanical switch SW2 con-
nected to P6[1] of CY8CKIT-030 or SW1 connected to P1[7] of CY8CKIT-001.
2. The LCD displays “Set Temp:".
Force the diode1 temperature to a known measured value between 0 °C and 100 °C, and enter
that temperature using the CapSense slider and buttons. Use the CapSense slider for coarse
temperature setting and the CapSense button for fine settings (P5_5/P0_5 to increment the tem-
perature in 0.1 °C steps and P5_6/P0_6 to decrement the temperature in 0.1 °C). After the tem-
perature is entered accurately, press the switch
SW2
in CY8CKIT-030 or
SW1
in CY8CKIT-001 to
calibrate.
3. The diode calibration constant is calculated from the measured temperature and the expected
temperature value entered by the user. After calibration, the LCD displays the message "Cali-
brated". Press
SW2
(CY8CKIT-030) or
SW1
(CY8CKIT-001) to go to the main menu temperature
display.
Figure 5-13. Diode Calibration
T
q
k
------
V
1
V
2
–
I
1
I
2
----
ln
-------------------
=
Start
Set calibration
temperature (tIdeal)
Measure diode
temperature tMeasured)
Diode Cal constant =
tIdeal/tMeasured
Save the diode
calibration constants in
EEPROM
Enter the calibration
temperature using
CapSense button and
slider
Go back to the main
menu on next switch
press
