resistance and-temperature-sensors-applications

www.acromag.com 248-624-

1541

www.acromag.com 248-624-1541

P 248-624-1541

F 248-624-9234

390765 S Wixom Road, PO Box 437

Wixom, MI 48393-7037 USA

www.acromag.com

By: Donald Lupo

Resistance/Temperature Sensors & Applications

http://www.acromag.com


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Agenda

• Discuss Three Sensor Types

◦ Potentiometers/Slidewires

◦ Thermistors

◦ Resistance Temperature Detectors (RTD’s)

• Applications

• Construction

• Measurement Technique

• Acromag Amplifier Interface Solutions


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Potentiometer/Slidewire Sensors

• What Are They?

◦ Variable Resistance Sensors

◦ 3-Wire Terminal Resistor

▪ Two Ends and a Sliding Wiper

▪ Used as a Voltage Divider

◦ 2-Wire Terminal Resistor

▪ One end and Wiper (Rheostat)

▪ Used as a Variable Resistor

• Two Basic Types

◦ Rotary and Linear (Slider)

• Who Invented the Sensor?

◦ Johann Christian Poggendorff

(1796-1877) in 1841


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Potentiometer/Slidewire Applications

• How are they used?

◦ Manual Control of an Analog

Signals (ie; Voltage Divider)

◦ Position Adjust(ie; Gates/Valves)

◦ Position Sensing/Feedback (Servo

Controls)

◦ Speed/Motor Controls

◦ Temperature Controls

◦ Audio/Volume Controls

◦ Lighting/Dimmer Controls

◦ Circuit Gain/Bias/Attenuators

• Many Consumer/Industrial Apps


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Potentiometer Construction

• Wirewound

• Carbon

• Cermet

• Metal Film

• Conductive Plastic


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Measurement Technique

• 3-Wire Sensor (Position-Best)

◦ Stable Excitation Source

◦ Low Voltage/Power Exc

◦ Pot Value >=1000ohms for

lead wire resistance to be

negligible

▪ 20Awg, 0.01ohm/ft

◦ Pot Value as low as possible

for source impedance

purposes (ie; 10Kohm is 2500

ohms of source impedance)

◦ % of Excitation Measurement

◦ Op Temp Changes - Immune

• 2-Wire Sensor (Position-Good)

◦ Resistance Measurement

◦ Op Temp Changes - Affected


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Acromag New Solutions

Model TT234-0600

--USB Config

--Sink/Source

4-20mA Outputs

-- -40 to 80C Amb

-- CE, UL/cUL Div2

Model TT334-0700

--USB Config

--Universal V/I

Outputs

-- -40 to 80C Amb

--CE, UL/cUL Div2

http://www.acromag.com/catalog/995



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Thermistor Sensors

• What Are They?

◦ “Thermal Resistors”

◦ Variable Resistance to Temperature

◦ Low Ranges (-90 to 130C), High Res

◦ 2-Wire Connection, Fast Response

• Two Basic Types

◦ PTC – Positive Temp Coeff.

◦ NTC – Negative Temp Coeff.


◦ Discovered 1833, Michael Faraday

▪ Silver Sulfide behavior

◦ Invented 1930, Samuel Ruben


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Thermistor Applications


◦ PTC – current limiter, fuse

◦ PTC – degaussing circuits in CRT

◦ PTC – heaters

◦ NTC – PS inrush current limiter

◦ NTC – Temperature Monitoring

▪ Resistance Thermometers

▪ Incubators, 3D Printers, Batteries

▪ Automotive Coolant/Oil

▪ Engine Manifold Temps

▪ Food Industry, Processing Equip

▪ Consumer Appliances – Toasters,

Coffee Makers, Freezers, Dryers


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Thermistor Construction • PTC

◦ Doped Polycrystalline Ceramic

▪ BaTiO3

◦ Plastic/Carbon Grains

◦ W. Heywang & G H Jonker

modeled in 1960’s

• NTC

◦ Semiconductor

▪ Pressed Disc or Cast Chip

• Steinhart-Hart Equation

1/T =A+B(ln R)+C(ln R)^3

T=Kelvins, R= Resistance

A,B,C = Steinhart-Hart parameters


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Temperature

Sensor

Comparisons

Advantages &

DisAdvantages

--Source:

Agilent

Technologies


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Measurement Technique • 2-Wire Sensor (NTC-Temps)

◦ Voltage Divider Measurement

◦ Stable Excitation Source

◦ <=3K Thermistor Ranges, typ

▪ 0-150C (10K to 0 ohms)

▪ -40 to 150C (100K to 0 Ohms)

◦ 5K-10K Thermistor Ranges,typ

▪ 0-150C (30K to 0 ohms)

▪ -40 to 150C (240K to 0 ohms)

◦ High Ohms/C output

◦ Needs Linearization to Temp

◦ Leadwire Resistance - Neg


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Model TT234-0600

--USB Config

--Sink/Source

4-20mA Outputs

-- -40 to 80C Amb

--CE, UL/cUL Div2

Model TT334-0700

--USB Config

--Universal V/I

Outputs

-- -40 to 80C Amb

--CE, UL/cUL Div2




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Acromag New Solutions – Thermistor Continued


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Resistance Temperature Detector (RTD) Sensors

• What Are They?

◦ Variable Resistance Sensors

◦ Used for Temperature Measurement

◦ Uses the temperature coefficient of

base metals

• Three Basic Sensor Types

◦ Platinum (100/200/500/1000 ohm)

◦ Copper (10 ohm)

◦ Nickel (120 ohm)


◦ Werner Von Siemens, 1871

◦ Hugh Longbourne Callendar, 1885

◦ Callendar-Van Dusen, 1925


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RTD Applications


◦ Precision Temperature

Measurements

▪ Contact

▪ Non-Contact

◦ Range: -200 to +500C range

◦ Heaters, Liquids, Air Flow, MCC

◦ Motor Winding’s/Bearing Temp

◦ HVAC, Environmental Controls

◦ Sanitary/Pharm/Food/Dairy/Bev

◦ Alt. to TC’s and Thermistors

• Many Consumer/Industrial Apps


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RTD Construction

• Thin Film

• Wire-Wound

• Coiled

• Others:

◦ Carbon

◦ Strain Free

• 2,3,4-Wire Sensor Connection

◦ 2, No Lead-wire Compensation

◦ 3, Good Lead-wire Compensation

◦ 4, Best Lead-wire Compensation


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Temperature

Sensor

Comparisons

Advantages &

DisAdvantages

--Source:

Agilent

Technologies


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Measurement Technique • 2-Wire Connection (Poor)

◦ No-lead wire compensation

◦ Keep lead wires short

◦ Can be “failsafe”

• 3-Wire Connection (Good-typ)

◦ Includes lead-wire

compensation (ie; 3rd wire

benefit)

◦ Lead wires should be balanced

◦ Can go long distances, 10ohms

per leg typical

• 4-Wire Connection (Best)

◦ Includes lead wire

compensation (2 Exc, 2Sense)

◦ Kelvin Type Connection

◦ Leads don’t need balance


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Model TT235-0600

--USB Config

--Sink/Source

4-20mA Outputs

-- -40 to 80C Amb

--CE, UL/cUL Div2

Model TT335-0700

--USB Config

--Universal V/I Output

(+/-10Vdc,+/-20mA,

4-20mA)

-- -40 to 80C Amb

--CE, UL/cUL Div2




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TT230 – Universal 4-20mA w/ Sink/Source Output


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TT330 – Universal Voltage/Current Output


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Summary

• Potentiometers/Slidewires

◦ Position Sensor, Resistance, Linear

▪ 3-Wire Sensed as Voltage Divider

▪ 2-Wire Sensed as Rheostat

◦ Used for Manual Control/Adjust

◦ 3-Wire Connection – Best, typical (Position)

◦ 1000ohm, 2000ohm, or <10Kohm best

• Thermistors

◦ NTC most popular for Temperature Sensing

◦ 2-Wire Sensor, Narrow Ranges: 0-100C,

◦ Low Cost, Fast Acting, but Non-Linear

• RTD’s

◦ 100ohm PT, 385 most popular

◦ Wider Temperature -200 to 500C

◦ Slow Response, High Accuracy, Stable


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• Questions?

• For More Information:

◦ www.acromag.com/tt

◦ Tel. 248-295-0880

◦ Email: [email protected]

Thank you!

http://www.acromag.com/tt



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resistance and-temperature-sensors-applications

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