TMPSNSRD-TCPL1 Microchip Technology, TMPSNSRD-TCPL1 Datasheet - Page 8

• Manufacturer Part Number: TMPSNSRD-TCPL1
• Description: BOARD RTD REFERENCE DESIGN
• Manufacturer: Microchip Technology

Specifications of TMPSNSRD-TCPL1

• Sensor Type: Temperature, Thermocouple
• Embedded: No
• Utilized Ic / Part: MCP3421, MCP9804
• Processor To Be Evaluated: MCP9804, MCP3421
• Interface Type: USB
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Supply: -
• Interface: -
• Sensitivity: -
• Sensing Range: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Oscillator Circuits for Sensors
Oscillator Circuits for Sensors
8
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.
Signal Chain Design Guide
R
V
V
1 =
DD
R
R
DD
5
6
RTD
V
DD
A
/2
C
1/4
C
–
+
1
R
5
C
2
MCP6294
MCP6234
MCP6004
1
4/4
R
+
–
V
3
MCP6294
MCP6234
MCP6004
DD
R
1 =
R
2 =
RTD
–
+
RTD
V
V
A
DD
R
DD
B
1
/2
4
V
MCP6541
MCP6561
DD
2/4
–
+
/2
C
2
MCP6294
MCP6234
MCP6004
R
V
3
OUT
V
DD
/2
3/4
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
■
■
■
Capacitive Sensors
■
■
■
Related Application Notes:
AN895: Oscillator Circuits for RTD Temperature Sensors
AN866: Designing Operational Amplifier Oscillator Circuits
Available on the Microchip web site at:






C
MCP6294
MCP6234
MCP6004
–
+
RTDs
Humidity
Thermistors
Humidity
Pressure
Oil Level
4
R
4
for Sensor Applications
Attributes:
• Precision dual Element RTD
• Reliable Oscillation Startup
• Freq. ∝ (R
Sensor Circuit
Attributes:
• Low Cost Solution
• Single Comparator Circuit
• Square Wave Output
• Freq. = 1/ (1.386 x R
R
1
7
x R
V
DD
2
/2
)
1/2
+
–
MCP6541
MCP6561
R
8
www.microchip.com
1
V
x C
OUT
1
)