Questions tagged [thermistor]

A device that is used to detect temperature - the word is a portmanteau of thermometer and resistor. The detection mechanism is the measurement of resistance which changes predictably with temperature.

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LED detector application for open and short circuit of 10K value thermistor

I am using an application where eight 10K thermistors wires are connected to a wearable device. The thermistors are stiched to the wearable device. We can determine the open and short circuit of the ...
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How to understand B values of thermistors for different temperature levels?

E.g. the datasheet of NCU18XH103F6SRB mentions different B values for pairs of temperatures (reference temperature to a higher one). For reference, here the values of this chip: [T]=degC [R]=kOhm [B]=...
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Replacing a thermistor sensor with a common resistor to 'trick' it

Here's the catch: we have a device that has a sensor that helps shutting it down when air temperature is too high. This sensor is based on a thermistor. We are now switching to a more powerful cooling ...
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NTC sensor in a Wheatstone bridge [closed]

I put an NTC sensor into a Wheatstone bridge so it gave me a totally non linear curve (positive and negative). How can I make it linear to read it by a microcontroller? Thanks.
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Improve accuracy of thermistor circuit

I am using this thermistor to measure temperatures between room temp and 100C and I want to design the circuit in such a way that it reads as accurately as possible (ideally +/- 2 degrees). I'm using ...
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2 votes
1 answer
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Limiting cold-start current of an SMPS by an NTC

I'm using this SMPS (12 VDC, 12.5 A model) and in my application in steady state the SMPS draws much less than one ampere from the AC line. But as you see its datasheet mentions its cold-start (inrush)...
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Grounding sensors to large bodies

I've attached a diagram of what I'm talking about. I have a large (600x300x10 mm) aluminum block in which I place thermistors to monitor the temperature distribution in the plate (in a standard ...
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Bigger NTC = better protection?

A 2.5 ohm NTC is used in the following PFC booster. I've got a 20 ohm one. Can I use it instead of 2.5ohm one? Does it provide better protection or does it disturb the normal operation of the circuit?
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Are inrush thermistors thermally insulated?

Vaguely related to this question but with some different questions and a different component. For an inrush-limiting NTC thermistor such as the Ametherm SL series: It seems purposefully designed to ...
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High Voltage DC Motor (AC rectification) Relay, Current Limiting, and Smoothing Capacitor

Looking at controlling a HVDC motor like so - Type DC781 (2) LSG Operates on 6 - 220 VDC 84 ohm terminal - terminal resistance No load speed of 8000 RPM @ 220 VDC - 100 mA Stall current at 220 VDC: 2....
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Relay contact sticks-Led driver

I m using relay 230vac/10amp to switch on/off LED driver. But sometimes relay sticks. Loads are nowhere close to 230v*10amp=2300watts. I cant understand what is causing this. i tried connecting an NTC ...
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In what ways does NTC thermistor quality affect measurements?

I've been looking at standard (i.e. 10 kohm, -50C to 150C) NTC thermistors and am wondering what the tradeoffs are for quality vs cost for applications where +-1C is acceptable accuracy. For instance, ...
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3 votes
3 answers
87 views

Should ADC reference pin also be a kelvin connection?

Reasking this question with a proper schematic: I am doing a ratiometric measurement of a Thermistor. The thermistor is located over 5 metres away from the ADC and all other components. This is going ...
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RC low pass filter for NTC

I want to measure temperature using an NTC resistor and ADC (of an MCU). A low pass input filter is required with a certain cutoff frequency. Here is the recommended schematic: So I replace ...
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What resistor network topology to use when measuring thermistors in a battery pack

Some EV competitions require that 20% of the cells in a battery pack be monitored for temperature, and go on to strongly recommend that it be 100%. Considering that batteries can easily contain ...
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Question regarding thermistors and ohmic heating

I am unsure why these answers are so. My attempts were black, the correct answers were red. A test is coming up in 10 hrs so any feedback would be nice. For Q9, I thought thermistors were made of semi-...
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5 votes
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446 views

Choosing register value for NTC with voltage divider

I need some help to choose resistor for voltage divider circuit to read temperature using NTC Thermistor. I'm planning to use STM32 with his 12bit ADC. The NTC I'm using has the following properties: ...
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2 votes
4 answers
412 views

How to turn a normally-closed temperature control circuit into a normally-open one?

I've designed a very simple heating circuit that runs a heater until a certain temperature has been reached (as measured by an NTC thermistor) at which point the heater turns off. The circuit diagram ...
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2 votes
2 answers
231 views

Linearization of thermistor

Thermistors are highly nonlinear devices . This linearization circuit of a NTC produces a linear response (temperature/resistance).But what should be the values of \$R_{s}\$ and \$R_{p}\$? Image from: ...
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1 answer
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NTC thermistor circuit design - obtaining resistance values

I am trying to solve this circuit in order to compare to regular Op Amp thermistor circuits. I'm using R4 as an NTC thermistor that ranges from 25ºC (6.24kOhm) to 40ºC (2.663kOhm), and VCC as 5V and i ...
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Voltage reference to drive multiple thermistors - high precision with op amp to supply current, or just generic voltage ref?

I would like to drive 8 thermistors in parallel. They will be driven from 2.5V in a voltage divider. This will be about 20mA current draw. I will be using a ratiometric measurement where the ADC ...
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Does NTC temperature measurement need calibration?

I'm creating some temperature sensors for home use. To measure outside and rooms' temperatures. Range from -30 °C to +50 °C. Temperature measurement is based on 10k NTCs SDNT2012X103F3950FTF (B=3950K, ...
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Why did the output voltage of this circuit had the same value no matter what the value for the resistor R2 was

So here is the circuit: R2 is a NTC thermistor (its value changes with temperature) and i want vout, the output of this circuit, to be in between 0.05V and 4.95V, where 0.05V should correspond to R2 ...
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274 views

Why does a voltage divider linearize the effects of a non-linear thermistor?

I saw a design specification with an NTC thermistor in a voltage-divider configuration. The design method said that we must have $$R_1=\sqrt{R_{NTC\min}R_{NTC\max}}$$ to produce a linear output ...
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Identify temperature sensor in thermostat

I somehow managed to damage the temperature sensor in my thermostat while cleaning corroded battery contacts. Apparently the only fix is "buy a new thermostat", though it is a pity to ...
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5 votes
4 answers
670 views

Averaging thermistor readings

I have 9 thermistors arranged in a grid, and I want to average the readings from these thermistors without code (that is, average them in a circuit rather than reading all the values into a ...
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NTC for inrush for DC/DC with DC input voltage

I want to limit the current to my DC/DC input. At first, I wanted to use a resistor, however, I also came across an NTC for inrush limiting. So I basically want to change R1 with an NTC. The specs for ...
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Li Ion cell charging and thermistors

I am designing a circuit to charge a small Li Ion flat cell with a capacity of around 300mAh. I want to charge it at around 75mA to 150mA max in the CC part of the cycle. It will always be charged ...
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1 answer
162 views

Temperature sensing with NTC circuit

I am reading through this document by TI on designing a temperature sensing circuit with an NTC thermistor. I'm having some trouble understanding the design steps though. Here are some snippets from ...
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Using two thermistors instead of one on battery protection IC

I'm making a battery protection board for a 3S1P pack. I wanted to include two thermistors in the pack to monitor the cell temperature because of how I want to position the batteries. The batteries ...
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Is it possible to calculate the optimum load resistor value for a thermistor?

In order to calculate the load resistor for a thermistor, we took the thermistor values over temperature (-40 (1kΩ )--> +86C (320kΩ)) and then tried a variety of load resistor values until the ...
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Need help with a replacement thermistor

I recently bought a used IKEA ceiling light however when getting it home noticed that it seems the live wire is connected to a thermistor? which then has another short wire where you connect to mains ...
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1 answer
78 views

What can I do to see only the logical values in the MOSFET input?

(Animated GIF of the simulation is here) This is a simple circuit that makes the MOSFET turn off, as the temperature of the NTC thermistor rises. As you increase the temperature in the diagram, the ...
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2 answers
140 views

Curly Symbol in RTD PTC Thermistor

What is the meaning of the "curly" symbol close to the double up arrows (Positive Temperature Coefficient, PTC) thermistor symbol? . (Ref.1, Ref.2)
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Stm32f103 adc stable conversion

I am making a ntc thermometer with stm32f103c8 (by writing over registers without using state library). The code works as it is,I did the adc conversion in 7.5 cycles. I used the calibration register ...
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1 answer
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Calculate NTC Temprature. but witout series resistor

Hello I have NTC Connected on PCB which configure as shown in following schematics. The problem is that I can not apply Steinhart-Hart equation because there is no resistance connected in series to ...
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3 answers
236 views

How to measure the temperature of a surface using an Arduino?

I'd like to measure the surface temperature of of a metal surface, to see how much that metal surface is heating up. I'm trying to recreate The EngineGuard. The EngineGuard uses a 10mm washer, that ...
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Will a 3S-3P NTC-array improve noise or self-heating?

I recently asked a question, "Tradeoffs for NTC Thermistors regarding 10K vs 100K vs 1Meg etc" where the answer was that noise for the 1Meg NTC would be greatest (10 times that of a 100K NTC....
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1 answer
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How to connect a thermistor to a micro-controller?

I was following a datasheet of a micro-controller and I got confused. I have two thermistors (LM 35DZ & TMP36GT9Z.) I would like to connect them to an evaluation board. The picture shows how: How ...
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3 answers
221 views

What is the difference in power consumption between thermocouple and thermistor?

I am working on a project to transmit sensor data and I chose to go with a temperature sensor to connect to a micro-controller. Since I care a lot about power consumption for my project, I would like ...
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3 answers
369 views

Tradeoffs for NTC Thermistors regarding 10K vs 100K vs 1Meg etc

I would like to make multiple strings of sensor having about 10 thermistors per string, each wired individually, but terminating at different lengths so that they're evenly spaced along each string. ...
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1 answer
77 views

Picking up EMI when measuring NTC near laser causing board reset

I tried searching for this to no avail. I hope I'm not all too wrong asking it here. I have set up my 60W CO2 Laser with a SKR 1.4 Turbo board and connected a 10k NTC thermistor to measure the ...
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1 vote
2 answers
94 views

Switch on and off a relay based on two different thermistor values

I am planning to add an electric fan to cool down an old car's radiator based on coolant's temperature. I have a temperature sensor of which I know the resistance/temperature profile. Let's say when ...
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Laser printer heater tricking

I use the toner transfer method to create PCBs. By removing the heat fuser from a laser printer and printing on gloss paper gives me wonderful results. The heat fuser and thermistor sensor is still ...
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I have an MZ4 thermistor, I can't find info about the value of capacitance

I have bought a self assembly kit for power source (based on the LM317). The provided small thermistors are tagged as MZ4. I did my research but couldn't find the datasheet. The PCB is showing them to ...
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Inrush Surge Limiter [NTC Thermistor] on Primary or Secondary side of Linear Power Supply

In designing a linear power supply, I understand I need to limit the inrush surge current on cold start, to charge up the large bank of filter capacitors, post-rectifier. However, my original intent ...
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Using a 10K ohm thermistor as a 5K

I have a water cooler that is using a B3950 10K sensor. For energy saving reasons, the microcontroller is limited to 6 degrees celsius (R=24k for the 10k ohm) I can't modify the microcontroller or how ...
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1 vote
2 answers
177 views

Why is there a resistor in this circuit?

Why there is a 220 ohm resistor in this circuit? Can't we just connect the thermistor directly to the base of transistor?
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can two separate circuits use the one sensor

I want to monitor the temperature of my washing machine. I was going to connect a raspberry pi up to the thermistor at the bottom of the drum. Would this interfere with how the washing machine ...
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2 answers
151 views

Is this the correct way to make a temperature activated fan?

This circuit is being used outside a PC. simulate this circuit – Schematic created using CircuitLab EDIT: @SupaNova The speed will increase with temp and the cutoff temp is 75℉.
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