AN897 Datasheet, PDF (11/16 Pages) Microchip Technology – Thermistor Temperature Sensing with MCP6SX2 PGAs

APPENDIX A: SET-UP OVERVIEW
A.1 Thermistor PGA PICtail Daughter
Board
The Thermistor PGA PICtail Daughter Board contains
the analog circuitry represented in Figure A-1. The
thermistor converts its temperature to a resistance. The
voltage divider then converts that resistance to voltage
and sends it to the CH0 input of the PGA. The PGA
gains and buffers this voltage and sends it off-board.
Board power is applied at the +5V and GND inputs. The
SPI™ bus makes it possible to control the PGA; its gain
and input channel can be set as desired from the
software.
Thermistor PGA
PICtail™ Daughter Board
Temperature
+5V
Test Point
GND
Test Point
Thermistor
Voltage
Divider
+5V
GND
CH0 Input
Test Point
CH1 Input
Test Point
PGA
MCP6S22
4
SPI™ Bus
V_OUT
FIGURE A-1:
Thermistor PGA PICtail™
Daughter Board Block Diagram.
The test points make it easier to test key points in the
circuit, change the input signals and to use this board
as a stand-alone board.
• GND Test Point – Connected to the ground plane
and is a convenient ground point for any lab
equipment
• +5V Test Point – Allows measurement of the
positive supply voltage and provides a means to
power this board with a laboratory power supply
• CH0 Test Point – The place to measure the volt-
age divider’s output (also the PGA’s CH0 input)
• CH1 Test Point – Makes it possible to send any
desired signal to the PGA
More detail on setting up this demonstration board can
be found in the “Thermistor PGA PICtail™ Daughter
Board User’s Guide” [12].
AN897
A.2 Associated Tools
Figure A-2 shows the block diagram of the hardware
and software tools that the Thermistor PGA PICtail™
Daughter Board is designed to work with. More
information on these tools can be found in the
“References” section.
Hardware
Software
PC
PICkit 1 Signal Analysis
PC Program
USB
PICkit™ 1
Flash Starter Kit
PICkit 1
Firmware
14
Signal Analysis
PICtail Daughter Board
PICA2Dlab.hex
Firmware
14
Thermistor PGA
PICtail™ Daughter Board
FIGURE A-2:
Diagram.
Measurement Setup Block
 2004 Microchip Technology Inc.
DS00897B-page 11