参数资料
型号: TSSOP20EV
厂商: Microchip Technology
文件页数: 8/30页
文件大小: 0K
描述: BOARD EVAL FOR MCP43X
标准包装: 1
主要目的: 裸评估板
嵌入式:
主要属性: TSSOP-20/16/14/8 和 SSOP-20 评估板
次要属性: 用于 PICmicro? MCU、ADC、DAC 和其它设备
已供物品: 5 裸板,文档
产品目录页面: 659 (CN2011-ZH PDF)
Oscillator Circuits For Sensors
RC Operational Amplifier Oscillators
For Sensor Applications
Op Amp or state-variable oscillators can be used to
accurately measure resistive and capacitive sensors.
Oscillators do not require an analog-to-digital converter and
provide a sensor measurement whose conversion to digital
has an accuracy limited only by the reference clock signal.
State-variable oscillators are often used in sensor
conditioning applications because they have a reliable
start-up and a low sensitivity to stray capacitance.
Absolute quartz pressure sensors and humidity sensors
are examples of capacitive sensors that can use the
state-variable oscillator. Also, this circuit can be used with
resistive sensors, such as RTDs, to provide temperature-to-
frequency conversion.
The block diagram below shows a typical system
level design, including the state-variable oscillator,
PIC microcontroller and temperature sensor (used for
temperature correction).
Sensors and Applications
Resistive Sensors
■ ? RTDs
■ ? Humidity
■ ? Thermistors
Capacitive Sensors
■ ? Humidity
■ ? Pressure
■ ? Oil Level
Related Application Notes:
AN895: Oscillator Circuits for RTD Temperature Sensors
AN866: Designing Operational Amplifier Oscillator Circuits
for Sensor Applications
Available on the Microchip web site at: www.microchip.com
Oscillator Circuits for Sensors
C 1
C 2
C 4
R 1 = RTD A
R 2 = RTD B
R 4
R 8
V DD /2
MCP6294
1/4 MCP6234
MCP6004
V DD /2
MCP6294
2/4 MCP6234
MCP6004
R 3
V DD /2
3/4 MCP6294
MCP6234
MCP6004
R 7
V DD /2
+
MCP6541
MCP6561
V OUT
V DD
Attributes:
R 5
V DD
? Precision dual Element RTD
Sensor Circuit
R 6
C 5
+
V DD /2
? Reliable Oscillation Startup
? Freq. ∝ (R 1 x R 2 ) 1/2
4/4 MCP6294
MCP6234
MCP6004
Oscillator Circuits for Sensors
R 1 = RTD
C 1
V DD
Attributes:
?
Low Cost Solution
R 2
A 1
MCP6541
MCP6561
V OUT
?
?
?
Single Comparator Circuit
Square Wave Output
Freq. = 1/ (1.386 x R 1 x C 1 )
V DD
R 3
R 4
8
Signal Chain Design Guide
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