Datasheet
6
Signal Chain Design Guide
Local Sensing
Local sensors are located relatively close to their signal
conditioning circuits, and the noise environment is not
severe; most of these sensors are single ended (not
differential). Non-inverting amplifiers are a good choice for
amplifying most of these sensors’ output because they
have high input impedance, and require a minimal amount
of discrete components.
Key Amplifier Features
■ Low cost
•
General purpose op amps
■ High precision
• Low offset op amps
• Zero-drift op amps
• Low noise op amps
■ Rail-to-rail input/output
• Most op amp families
■ High input impedance
• Op amps with CMOS inputs
■ Low power and portable applications
• Low power op amps
■ High voltage
• High voltage op amps
■ High bandwidth and slew rate
• High speed op amps
■ Load drive
• High output drive op amps
Classic Gain Amplifier
High Side Current Sensing Amplifier
+
pH Monitor
VOUT
MCP6XX,
MCP6XXX
-
–
+
R
SEN
I
SEN
R
1
R
2
VOUT
VREF
R
1
R
2
V
1
V
2
–
+
MCP6HXX
VDD
R
SEN
<< R
1
, R
2
VOUT = (V
1
– V
2
) + VREF
R
2
R
1
( )
Local Sensors
Sensors and Applications
Single Sensors
■
Thermistors for battery chargers and power supply
temperature protection
■ Humidity Sensors for process control
■ Pyroelectric infrared intrusion alarms, motion detection
and garage door openers
■ Smoke and fire sensors for home and office
■ Charge amplifier for Piezoelectric Transducer detection
■ Thermistor for battery chargers and home thermostats
■ LVDT position and rotation sensors for industrial control
■ Hall effect sensors for engine speed sensing and
door openers
■ Photoelectric infrared detector
■ Photoelectric motion detectors, flame detectors,
intrusion alarms
■ Sensing resistor for current detection
Multiple Local Sensors
■ Temperature measurement at multiple points on a Printed
Circuit Board (PCB)
■ Sensors that require temperature correction
■ Weather measurements (temperature, pressure,
humidity, light)
Capacitive Humidity Sensor Circuit
(PIC16F690DM-PCTLHS)
PIC16F690
MCP6291
V
DD
_
DIG
C1
U1
P4
100 nF
V
CM
V
DD
V
SEN
V
INT
R
INT
6.65 MΩ
C
SEN
I
INT
R
CM
1
20 kΩ
R
CM
2
20 kΩ
C
CM
100 nF
100 nF
C
CG
C
2
P3
P1
P2
U
2
–
+
Comparator
V
REF
SR
Latch
Timer1