Thermistors

Thermistors are thermally sensitive resistors and have either a negative temperature coefficient (NTC) or positive temperature coefficient (PTC) which means, in NTC as temperature increases, resistance decreases; and in PTC as temperature increases as temperature increases resistance increases.

Thermistors term is a combination of temperature and resistor.

Thermistors are made from metallic oxides. Thermistors are easy to use and less costly. Thermistors exhibit non linear characteristics.

NTC thermistors are made from metal oxides like specific mixtures of pure oxides of nickel, manganese, copper, cobalt, tin, uranium, zinc, iron, magnesium, titanium, and other metals where as PTC are made from semiconductor like silicon (silistors) or barium, lead, and strontium titanates with the addition of yttrium, manganese, tantalum, and silica. The negative exponential function that best describes the resistance-temperature (R(T)) characteristic of an NTC is given by Steinhart-Hart equation:

1

Where T is the absolute temperature in Kelvin and R the thermistor resistance at temperature T.

The graph is as shown below

2

Thermistors have the desirable characteristics of small size,narrow spans, fast response (their time constant can be under 1 s), and a very high sensitivity (about 2%/°F [4%/°C]), which usually increases as the measured temperature drops. Thermistors do not need cold junction compensation because their resistance is a function of absolute temperature, and errors due to contact or lead-wire resistance are insignificant because of their relatively small values. Unlike RTDs and TCs, they are well suited for remote temperature sensing. Thermistors are available in a great variety of configurations, are inexpensive, are not affected by polarity, and their stability increases with age. At present, they are typically more rugged and better able to support mechanical and thermal shock and vibration than other temperature sensors.They are the most sensitive differential temperature detectors available.

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Indian Penal Code

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RTD

https://kishorekaruppaswamy.in/2019/02/27/temperature-transmitter-rtd/

Hook up diagram

https://kishorekaruppaswamy.in/2019/02/27/instrument-installation-hook-up-diagram/

Calibration of Siemens Sipart PS2

https://kishorekaruppaswamy.in/2019/02/27/calibration-of-siemens-sipart-ps2/

Calibration of Rosemount TT

https://kishorekaruppaswamy.in/2019/02/27/calibration-of-temperature-transmitter-zero-trimming/

Control valve sizing equation

https://kishorekaruppaswamy.in/2019/02/27/control-valve-sizing-equations/

Control valve leakage classification

https://kishorekaruppaswamy.in/2019/02/27/control-valve-leakage-classification/

Bently Nevada VMS continued

https://kishorekaruppaswamy.in/2019/02/27/bently-nevada-vms-continued/

Intrinsically safe barrier

https://kishorekaruppaswamy.in/2019/03/07/intrinsically-safe-barriers/

I/P converter

https://kishorekaruppaswamy.in/2019/03/07/i-p-conveter/

Lapping of a control valve

https://kishorekaruppaswamy.in/2019/03/07/lapping-of-a-control-valve/

Limit switch

https://kishorekaruppaswamy.in/2019/03/09/limit-switch/

Dampers

https://kishorekaruppaswamy.in/2019/03/21/dampers/

Hookup diagram continued

https://kishorekaruppaswamy.in/2019/06/06/hook-up-diagrams-continued/

Instrumentation related to a motor driven pump

https://kishorekaruppaswamy.in/2019/06/07/instrumentation-related-to-a-motor-driven-pump/

Flow transmitter DP type

https://kishorekaruppaswamy.in/2019/07/19/flow-transmitter-dp-type/

Typical foundation fieldbus wiring

https://kishorekaruppaswamy.in/2019/08/02/a-typical-foundation-field-bus-wiring-diagram/

Painting procedures

https://kishorekaruppaswamy.in/2019/09/14/painting-procedure/

Instrumentation cable design specification

https://kishorekaruppaswamy.in/2019/09/15/instrumentation-cable-design-specification/

Standard power supply requirements of instruments

https://kishorekaruppaswamy.in/2019/09/15/standard-power-supply-requirements-for-instrumentation-devices/

Acceptable ranges of Instruments

https://kishorekaruppaswamy.in/2019/09/15/acceptable-accuracy-ranges-of-instruments/

Instrumentation general design requirements part 1

https://kishorekaruppaswamy.in/2019/10/09/general-design-requirements-of-instrumentation-part-1/

Instrumentation general design requirements part 2

https://kishorekaruppaswamy.in/2019/10/09/general-design-requirements-of-instrumentation-part-2/

Instrumentation general design requirements part 3

https://kishorekaruppaswamy.in/2019/10/09/general-design-requirements-of-instrumentation-part-3/

Instrumentation general design requirements part 4

https://kishorekaruppaswamy.in/2019/10/09/general-design-requirements-of-instrumentation-part-4/

Instrumentation general design requirements part 5

https://kishorekaruppaswamy.in/2019/10/09/general-design-requirements-of-instrumentation-part-5/

AS-i

https://kishorekaruppaswamy.in/2020/02/22/as-i-actuator-sensor-interface-protocol/

Boiler

https://kishorekaruppaswamy.in/2020/03/03/boiler/

Thermistors

https://kishorekaruppaswamy.in/2020/04/05/thermistors/

Profibus

https://kishorekaruppaswamy.in/2020/04/05/profibus/

3 element control

https://kishorekaruppaswamy.in/2020/04/05/three-element-control-in-a-boiler/

Ultrasonic flow measurement

https://kishorekaruppaswamy.in/2020/04/05/ultrasonic-flow-measurement-working-principle/

Parameter setting of  E+H LT

https://kishorekaruppaswamy.in/2018/04/29/parameter-setting-of-eh-fmp51-gwr-lt/ Siemens LT parameter setting

https://kishorekaruppaswamy.in/2018/04/29/parameter-setting-of-siemens-probe-lu-ultra-sonic-level-transmitter/

Parameter setting of KTek LT

https://kishorekaruppaswamy.in/2018/04/29/parameter-setting-of-ktek-mt-5100-gwr-lt/ Analysis of Pump Vibration

https://kishorekaruppaswamy.in/2018/06/08/analysis-of-motor-pump-vibration/ HART Communication

https://kishorekaruppaswamy.in/2018/06/17/hart-communication/ Instrumentation tube fittings

https://kishorekaruppaswamy.in/2018/03/28/instrumentation-tube-fittings/

Radar LT non contact type

https://kishorekaruppaswamy.in/2018/03/19/radar-non-contact-level-transmitter-working-and-parameters/

Rosemount GWR parameter setting

https://kishorekaruppaswamy.in/2018/03/15/parameter-setting-of-rosemount-gwr-5300-series-lt/

Offset calculation GWR

https://kishorekaruppaswamy.in/2018/02/14/offset-calculation-for-a-guided-wave-radar-level-transmitter/

Temperature transmitter types

https://kishorekaruppaswamy.in/2018/02/13/temperature-transmitter-classification-tree/

Flow transmitter types

https://kishorekaruppaswamy.in/2018/02/13/flow-transmitter-classification-tree/

Level transmitter types

https://kishorekaruppaswamy.in/2018/02/13/level-transmitter-classification-tree/

Pressure  transmitter types

https://kishorekaruppaswamy.in/2018/02/13/pressure-transmitter-classification-tree/

Piping and Instrument diagram

https://kishorekaruppaswamy.in/2018/02/04/pid/

Smoke detector working

https://kishorekaruppaswamy.in/2018/02/02/smoke-detector-working-principle/

Conductivity transmitter working

https://kishorekaruppaswamy.in/2018/02/02/conductivity-transmitters/

Gas detector working

https://kishorekaruppaswamy.in/2018/02/01/gas-detector-working-point-gas-detector/

Flame detector working

https://kishorekaruppaswamy.in/2018/02/01/flame-detector-working-principle/

Units and conversion

https://kishorekaruppaswamy.in/2018/01/05/units-and-its-conversion/

Specific gravity

https://kishorekaruppaswamy.in/2018/01/05/specific-gravity-of-selected-liquidsgases-and-saturated-waterfor-different-temperatures/

Instrumentation Interview questions

https://kishorekaruppaswamy.in/2018/01/03/instrumentation-interview-questions/

Temperature transmitter calibration

https://kishorekaruppaswamy.in/2017/12/20/temperature-transmitter-calibration/

Pressure transmitter calibration

https://kishorekaruppaswamy.in/2017/12/19/pressure-transmitter-calibration/

Magnectostrictive LT calibration

https://kishorekaruppaswamy.in/2017/12/19/magnetostrictive-level-transmitter/

Hazardous area classification

https://kishorekaruppaswamy.in/2017/12/17/hazardous-area-classification/

Excel short keys

https://kishorekaruppaswamy.in/2017/12/16/excel-short-keys/

Digital electronics

https://kishorekaruppaswamy.in/2017/12/14/digital-electronics/

Thermocouple mV conversion chart

https://kishorekaruppaswamy.in/2017/12/14/thermocouple-temperature-mv-conversion-chart/

Foundation field bus

https://kishorekaruppaswamy.in/2017/11/20/foundation-fieldbus/

Rosemount 3051 series transmitter

https://kishorekaruppaswamy.in/2017/11/20/rosemount-3051-series-transmitters/

Hydrogen sulphide

https://kishorekaruppaswamy.in/2017/11/20/hydrogen-sulphide-h2s/

Root cause Analysis

https://kishorekaruppaswamy.in/2017/11/20/root-cause-analysis/

Shore Key Line up

https://kishorekaruppaswamy.in/2017/09/28/how-to-line-up-interface-level-transmitter/

pH Analyser

https://kishorekaruppaswamy.in/2017/09/27/ph-analyzer-working-principle-and-calibration/

Mathematic Formula

https://kishorekaruppaswamy.in/2017/09/24/important-mathematical-formulas/

India

https://kishorekaruppaswamy.in/2017/08/15/india/

Oil in Water Analyser

https://kishorekaruppaswamy.in/2017/08/13/oil-in-water-analyzer/

BSW Analyser

https://kishorekaruppaswamy.in/2017/08/13/bsw-analyzer/

Capacitive Level Transmitter

https://kishorekaruppaswamy.in/2017/08/12/capacitance-type-level-transmitter/

LRV and URV Level Transmitter

https://kishorekaruppaswamy.in/2017/08/11/lrv-and-urv-of-interface-level-transmitter/

Instrument Loop Diagram

https://kishorekaruppaswamy.in/2017/07/28/instrument-loop-diagrams/

Laser Level Transmitter

https://kishorekaruppaswamy.in/2017/05/20/laser-level-transmitters/

Turbine Flow Transmitter

https://kishorekaruppaswamy.in/2017/05/20/turbine-flow-meter/

Zero Suppression and Elevation

https://kishorekaruppaswamy.in/2017/05/18/zero-suppression-and-elevation/

Bently Nevada 3500 VMS

https://kishorekaruppaswamy.in/2017/04/08/bently-nevada-3500-vms/

Control Valve Servicing

https://kishorekaruppaswamy.in/2017/04/08/smp-of-a-control-valve/

Safety Integrity Level

https://kishorekaruppaswamy.in/2017/02/23/safety-integrity-level-sil/

Instrumentation Working Principle

https://kishorekaruppaswamy.in/2017/02/22/instrumentation-working-principle-continued/

Instrumentation Gland Sizes

https://kishorekaruppaswamy.in/2017/02/15/instrument-gland-sizes/

LRV and URV of DP level transmitter

https://kishorekaruppaswamy.in/2017/01/02/lrv-and-urv-determination-for-d-p-type-level-transmitter/

Instrumentation working principle continued

https://kishorekaruppaswamy.in/2017/01/02/instrumenation-working-principle/

Level measurement using Pressure gauge

https://kishorekaruppaswamy.in/2016/06/10/level-measurement-using-pressure-gauge/

Tips and tricks in field Instrumentation

https://kishorekaruppaswamy.in/2016/04/18/tips-and-tricks-in-field-instrumentation/

Data Communication Protocol

https://kishorekaruppaswamy.in/2016/03/10/data-communication-protocols/

Pressure Unit Conversion

https://kishorekaruppaswamy.in/2016/02/19/pressure-unit-conversion/

Calibration of  GWR level transmitter

https://kishorekaruppaswamy.in/2016/02/19/calibrationtheory-and-initialization-of-gwr-level-transmitter-rosemount-5300-and-ktek-5100/

Control Valves

https://kishorekaruppaswamy.in/2016/02/18/control-valves/

ERS Level transmitter Parameters

https://kishorekaruppaswamy.in/2016/02/18/calibration-and-initialization-of-electronic-remote-seal-level-transmitter-rosemount-3051ers/

Calibration of wet leg tube Level transmitter

https://kishorekaruppaswamy.in/2016/01/16/calibration-and-initialization-of-wet-leg-impulse-tube-rosemount-3051cd-series-lt/

Calibration of capillary type Level transmitter

https://kishorekaruppaswamy.in/2016/01/15/calibration-and-initialization-of-rosemount-3051cd-capillary-type-level-transmitter/

mV conversion chart

https://kishorekaruppaswamy.in/2015/02/27/942/

Gulf JOB

https://kishorekaruppaswamy.in/2013/09/18/contact-details-for-gulf-jobs/

Reynolds Number

https://kishorekaruppaswamy.in/2012/11/28/reynolds-number/

Calibration of displacer type LT

https://kishorekaruppaswamy.in/2012/11/16/calibration-procedure-of-displacer-type-level-transmitter/

My profile

https://kishorekaruppaswamy.in/2012/06/20/click-here-then-photo-and-view-profile/

Chemical hazard pictogram

https://kishorekaruppaswamy.in/2012/04/04/chemical-hazard-pictograms/

RTD conversion chart

https://kishorekaruppaswamy.in/2012/02/17/calibration-of-dp-type-transmitter-with-actual-pressure/

Ingress Protection

https://kishorekaruppaswamy.in/2012/01/18/ingress-protection/

To know more about Instrumentation and Control,

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or

https://kishorekaruppaswamy.in/2012/09/30/basic-instrumentation-and-calibration/

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