choosing the right sensors for industrial applications
DESCRIPTION
Industrial sensing applications require special design considerations to address technical challenges. One of the main criteria that a user has to consider is the choice of technology used for the sensor. However, this is just the start. By watching this 1-hour webinar, you will gain a better understanding of the key factors necessary to make the best choice for your industrial sensing application of temperature, pressure and position sensors.TRANSCRIPT
Choosing the Right Sensors for Industrial Applications
This webinar will be available afterwards at
designworldonline.com & via email
Q&A at the end of the presentation
Hashtag for this webinar: #DWwebinar
Before We Start
Moderator
Randy Frank Design World
Presenters
Emmy Denton Texas Instruments
Tim Shotter All Sensors
Dan Bruski SICK
in
Industrial Environments
Emmy Denton
Applications Engineer
May 29, 2013
Temperature Sensor Applications
Temperature Sensors have
3 key functions in electronic
systems
• Calibration
• Monitoring & Protection
• Control
Temp sensing is
EVERYWHERE!
– Industrial: Factory Automation,
Medical, Down Hole Drilling,
Instrumentation …
6
Common Temperature Sensing Technologies
Criteria
ATS
Thermistor Thermocouple
RTD
Temp Range (°C) -55 to +150 (-55 to +200 digital)
-100 to +500 (-60 to +200 SMD)
-267 to +2316 -240 to 700
Accuracy Good Good Good Best
Linearity Best Least Better Better
Sensitivity Better Best Least Less
Circuit Simplicity Simplest Simpler Complex Complex
Power Consumption Lowest Low High High
Cost $ $ $$ $$$
7
Local Digital
Reports temperature at location of the
sensor
Small
Low Power
Popular Interfaces (I2C, SPI, One-wire …)
Highest Temp (200°C)
Highest Accuracy (0.5°C)
Ind. Standard (LM75)
Remote Digital
Measure any Diode, Transistor, or
CPU/GPU/FPGA
Multiple Channels
Int. Power Monitor
Beta Correction
Contactless IR
Measures passive IR to determine
object temperature without making
contact
Switches/Thermostat
Simple hardware over temperature
protection
Dual Alerts
Resistor Prog
Pin Programmable
Factory Preset
Analog Temperature Outputs
Fan Control /HW Monitors
Complex with Many Functions in
addition to temperature sensing
2 Wire Interface
Fan Control Monitor
Monitor & Control (ADC and DAC)
Voltage Comparators
Integrated Circuit Thermal Management Solutions
Local Analog
Voltage output proportional to
temperature
Smallest
Highest Accuracy
Lowest Power
Highest Temp
Most Popular
Low Cost
8
Downhole Drilling Tools
LM95172
• Located at the tip of the drill in order to
protect the other circuitry above
Reasons for Temp Sensing
• Over-Temp Protection of PCB Components
• Predict life expectancy of tool
• Customer billing purposes
• Tool Oil Degradation
Key Specifications
• Up to +200°C temperature range
• Digital Interface – redundant ADC
• High accuracy and resolution
• Alarm output and shutdown mode
• Requires reliability – additional qualification required
• Packaging must withstand extensive temperature
(usually ceramic or die)
Temp Range
(°C)
Accuracy (°C)
+130 to +160 ±1.0
+160 to +175 ±2.0
+175 to 200 ±3.0
+120 to +130 ±2.0
-40 to +120 ±3.5
9
Thermocouple Cold Junction Compensation
Reasons for Temp Sensing • Thermocouple measures difference temperature of two
junctions
– Junction at zone being measured
– Junction back to copper
• Required to determine temperature of zone being
measured
Key specifications
• Up to +70°C - 85°C temperature range
• ADC is usually available in AFE
• Accuracy added to accuracy of zone being measured
• Must be mounted on isothermal block for good temperature
conduction
T_cold
T_hot
10
Analog Temperature Sensing Options
• Most Micros Include Multiple Channel ADCs
• Analog Temp Sensor Advantages:
Higher accuracy over wider temperature range
Linear across temp range
Lower Power Dissipation – draw less than 10uA over temp range
Simpler design that utilizes less board space – no additional external components
Simpler to use
LMT84 Curve
11
ATS
THERMISTOR
Output Voltage vs. Temperature (°C)
ATS
THERMISTOR
vs.
ATS
12
Analog Temp Sensor Accuracy
• Accuracy is very linear for 96
units plotted
• ±0.7°C Max and Min Accuracy
over 0 to 150°C
• Sensing temps approaching
200°C possible
• Some Devices Can Achieve +/-
0.1°C Spread without
Temperature Calibration!
13
THANK YOU!
– Emmy Denton
All Sensors
PRESSURE SENSORS…
RESOLUTION AND BANDWIDTH
Typical Applications
All Sensors
Familiar Specifications • Pressure Range
• Sensitivity
• Offset
• Linearity
• Temperature Effects
• Accuracy
All Sensors
Compensation Techniques
All Sensors
Familiar Trade-offs
All Sensors
What Your Mom Didn’t Tell You…
All Sensors
System Basics Review
All Sensors
Application BW/Resolution
All Sensors
All Sensors
BW/Resolution Isolines
All Sensors
Possible Compensation
Revised BW/Resolution Trade-offs
All Sensors
• To know the location of something
• To move a target with respect to that known location
• Everything’s relative o Objects are positioned with respect to something fixed
o Key for evaluating specs like accuracy, repeatability, resolution
Focus application areas
• Positioning in manufacturing Knives, slitters, saws, welding tips, drills, tools
• Logistics Cranes, ASRS, shuttles, rail cars
What is “positioning?” What are we positioning?
Rotary and wire draw encoders
Linear magnetic encoders
Lasers Hybrid
Positioning Technology Choices
High speed
High resolution
Low cost
Slippage and wear
errors
Mechanical
High speed
High resolution
Rugged in challenging
environments
Difficulty with non-linear paths
Strict mounting requirements
Cost
Navigates non-linear paths
Path can be obstructed by other
vehicles or objects
Need to mount reference tape
Simple setup
Non-contact – long life
Many choices of range, precision,
outputs
Line of sight only
Optically challenging environments
Range
•Sensor must not only be able to measure the absolute distance from the sensor to the target to be positioned, but also have the appropriate span.
Resolution
•How small of a movement is need to be controlled?
Repeatability
•Repeatability is KEY. This describes how close to the desired location it will be when the sensor output indicates it has reached its final position
Output rate
•The output rate of the sensor is how often the sensor updates the measured position and needs to be matched up with the speed of the target.
Output type
•The output type simply needs to match the input of the control system/PLC/PC.
Selection Criteria
• A reflective target is preferred over natural targets for positioning o Strong and consistent signal return
o “Safe” – if reflector is blocked, an erroneous position is not returned
• Response time vs. output rate o Response time refers to lateral movement into the beam – used for detection, not positioning
o Output rate is what matters after the target is locked-in
• Accuracy trap o Don’t get hung up on an accuracy spec, because you don’t need it for positioning applications
until you replace a sensor
• Excess gain o Don’t worry about using a sensor with way more range than needed – this gives you useful
excess gain
• Long range alignment o Utilize vendor-supplied alignment brackets
Tips and Tricks
30
Questions?
Design World Randy Frank [email protected] Twitter: @SensorTips
All Sensors Tim Shotter [email protected] Phone: 408.225.4314 Twitter: @AllSensors
SICK Dan Bruski [email protected] Phone: 612.217.1326
Texas Instruments Emmy Denton [email protected] Phone: 408.721.3267
Thank You
This webinar will be available at designworldonline.com & email
Tweet with hashtag #DWwebinar
Connect with
Twitter: @DesignWorld
Facebook: facebook.com/engineeringexchange
LinkedIn: Design World Group
YouTube: youtube.com/designworldvideo
Discuss this on EngineeringExchange.com