Specifications

49Sensors
Overview
Introduction
Maxim oers a range of products
extending from sensors for
properties such as temperature, light,
acceleration, etc., to products that
shape and convert a sensor’s electrical
signals into usable information.
A sensor is a device that measures a
physical property and is generally used
to monitor and control an event or
process. Examples include sensors for
measuring the temperature of a room
or of a blast furnace; the pressure in a
tire or in a steam turbine; the weight
of an item purchased at the grocery
store or of a vat of molten steel. The
use of sensors permeates our personal
lives and our factories. We depend
inextricably on the operation and
accuracy of sensors to ensure we are
receiving the goods and services that
we paid for to live more productive
and comfortable lives and to run our
industrial processes safely and eciently.
A complete sensor assembly includes a
transducer (to transform one physical
quantity to another: weight, pressure,
temperature, humidity, acceleration, or
light to an electrical signal), a housing,
signal conditioning and communications
circuitry, and a connector. Some
transducers are resistive elements that
require external excitation to create a
measurable voltage. Other transducers
generate their own voltages or currents
in response to physical properties.
The signals coming from transducers
are usually very small and require
optimized interface circuits to provide
adequate gains without introducing
noise that reduces accuracy. Sensor
assemblies are often located far
from their processing point, so along
with signal amplication, the sensor
knowledge domain also includes signal
communications to ensure the delivery
of accurate signals to a processing point.
The sensor “signal chain” requires
processing for sensor excitation, sensor
amplication, signal ltering and
conditioning, and the transformation
of signals from the analog-to-digital
domain, and sometimes back again.
Outside the signal chain there are
other stringent requirements for power
provisioning and management, as well as
signal communication among devices/
systems and secure data transmission.
CompoNet
HART
IO-LINK
DIGITAL IO
RS-485
Ve
R
R
R+∆R
R-∆R
EXCITATION
FEEDBACK
MISCELLANEOUS
POWER SUPERVISORS TIMING
PRECISION
RESISTORS
TEMP
SENSORS
PGA
IA
FILTERS
REFERENCE
OP AMPS
DIGITAL
POTENTIOMETERS
PRECISION
RESISTORS
ADC
TOUCH
SCREEN
μC
DAC
DAC
OP AMPS
REF
TRANSDUCER /
BRIDGE
AFE FILTER ADC COMMUNICATIONS
= MAXIM SOLUTION
DIGITAL DOMAIN
INTEGRATED SIGNAL CONDITIONER
+
–
+
–
+
–
Block diagram of a basic sensor system for industrial processes. For a list of Maxim’s recommended sensor solutions, please go to: www.maxim-ic.com/sensor.