Questions tagged [thermocouple]

A thermocouple is formed by a contact of two (2) dissimilar conductors. The voltage across thermocouple is governed by Seebeck effect. Thermocouples are widely used as temperature sensors.

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Using Thermal Epoxy vs Super Glue for Thermal Couple temperature measuring

Which practice is better for measuring the temperature if a MCU on a PCB with a thermocouple: Measuring on the case of the MCU with thermal epoxy attached to the thermal couple, or super glue? I feel ...
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40 views

Confused about MAX6675 thermocouple sensor SPI protocol

I'm using an AVR microcontroller to take readings from a MAX6675 (SPI K-type thermocouple ADC chip). I am having difficulty understanding what is required by this chip's SPI interface. The datasheet (...
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55 views

K thermocouple readings bad probe or circuit?

I recently put together this circuit to read a K thermocouple. It takes the probes reading and converts it into an analog voltage. The design came from: I am getting poor readings from the circuit ...
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113 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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159 views

Why is this thermocouple amplifier with analog output circuit not working?

I am trying to assemble a circuit based on this datasheet: The schematic I derived from the circuit is: This was made into a PCB footprint The readings I am getting from this circuit are much too ...
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98 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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21 views

Variation of neutral temperature in a thermocouple

Neutral temperature =-(a÷b), where a and b are constant for metals A and B, but the inversion temperature = -2(a÷b), but inversion temperature depends upon the cold juction so why is the neutral ...
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113 views

Best way to get measurements from 16 K-type thermocouples with an MCU?

I'm working on a project, which is focused on taking frequent (250ms interval or smaller) measurements of extreme temperatures (0-700 C) in 16 points. I need to take measurements of multiple ...
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89 views

My soldering station's iron is rated for 70W, can I modify a 75W one to work with it?

I have an Aoyue 936A soldering iron rated at 24V/70 watts. I came across a cheapo soldering iron rated at 24V/75W and rewired it according to the pinouts of the original one. The thermocouple readings ...
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34 views

MAX 6675 K-type unstable to say the least

have two breakout boards with MAX6675. I have 3 different K-type thermo elements. The MAX is connected to an AVR (atmega8) for communication, driver my own, communicates to PC on UART. Now none of the ...
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29 views

Need to identify faulty thermistor in order to find a like or better replacement

I have an ic with a poorly performing thermistor I'd like to replace with a more accurate, more sensitive component. The first step is finding out what thermistor I likely have or at least who made it....
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103 views

Cold-junction point

I'm converting an kitchen top oven into a reflow oven and all seems fine except for the temperature measurements. Using the same K-type thermocouple, but an external cold junction, the measurements ...
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83 views

Noise equivalent power of thermopile sensor?

I am working on the characterisation of thermopile sensor and stuck in determining the NEP of the sensor. My thermopile sensor with AD8630 amplifier receives IR radiation coming from the blackbody at ...
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48 views

Understanding thermocouple transmitter wiring

I'm trying to use the RMTJ40BD thermocouple (page 12) and I'm having trouble understanding the wiring diagram for the output. The manual says that Vo and OPG are the outputs but what is OPG, what ...
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50 views

How are analog thermocouple meters calibrated?

In most modern thermocouple measuring equipment, the input is high impedance and approximates a perfect voltmeter. This makes the thermocouple measurement easy because there is no current flowing ...
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73 views

Thermocouple troubleshooting

I have a system error pop-up on an HMI of one of my machines. Since it only had a number, I tried to reach the manufacturer for the error code description. They said that this error usually is the ...
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178 views

Thermocouple simulator circuit : isolation & voltage reference

I'm designing a multi-channel (6-10) thermocouple simulator. For different reasons, all the outputs must be isolated to simulate completely the behaviour of the real-life thermocouple. To do the task ...
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77 views

How to amplify a thermocouple that shares a wire with a heating element (soldering iron?)

I have a problem that I can't seem to wrap my head around. I am designing a controller for a JBC handpiece, but the cartridgess are only three pins (JBC Nano only two.) I'm trying to design a ...
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63 views

Max31855k - fluctuation and drift

I'm using a b 31855k breakout board (a chinese one at that) with the olimex A20 and a K-type thermocouple (which works OK on another device with the 31855k). The problem is, that the thermocouple temp ...
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135 views

Thermocouple comparator choose

I measured the parameters of a thermocouple (R1). R1in=5 Ohm, V=1..10 mV (measured by multimetr). Ipositive = 5v/20000 = 0,25mА, and Upositive max = 0,25 * 0,001 * 100 = 25mV I have lm339, lm324. ...
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77 views

How to keep heat away from an electronics enclosure?

I’m converting a simple cooking hot plate to have it’s temperature controlled by an arduino, with an lcd. It’s metallic casing gets really hot when the plate is turned on. As I’ll remove the original ...
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194 views

Building a furnace with more than one thermocouple for accurate temperature measurement

I am a mechanical engineering student. I am in the process of making a special purpose heating equipment. It could be considered as a 3 phase electrical resistance furnace. I want the temperature in ...
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76 views

How to measure extremely high temperatures?

I'm interested in building or buying an electric (arc or induction) furnace for smelting & heat-treating metals. Most designs I've seen utilize PID controllers and thermocouples. How are extreme ...
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1k views

Effect of length on a thermocouple's accuracy

I'm a mechanical engineer working on acquiring some temperature data using thermocouples. Q. I wanted to know the effect of wire length on a thermocouple's accuracy. I don't have much of electrical ...
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225 views

Thermopile temperature sensor

I am using an MRT511 thermopile temperature sensor and COS77DT for amplifying the temperature sensor output. I used Recommended circuit in the MRT511 datasheet but output voltage of the op-amp not ...
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34 views

2 outputs of same op amp gives different voltages

I am using lm358p op-amp for 2 different heaters I connected both of them in a single op-amp and it didn't work firstly I thought that the problem was thermocouples I swapped them but the problem kept ...
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73 views

How to access a Thermocouple signal in PC?

I'm looking for the way to access a thermocouple signal to use it in my own software. I suppose that I have to place a data acquisition system (something like this https://www.dataq.com/data-...
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302 views

Thermocouple amplifier and cold junction compensation

I am trying to design a thermocouple amplifier with cold junction compensation. I already designed a simple amplifier for the thermocouple using LM358. Note that I can built this entire circuit using ...
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2answers
358 views

Thermocouple Equivalent Circuit

I am about to design an amplifier to J | K Thermocouples, but I have been unable to find a trustable equivalent circuit|model|specs for them. I know a J Type Thermocouple has some general specs, such ...
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46 views

Regulating precision heating

Whats the simplest electr(on)ic(al) method for heating a coil or similar element to a specific temperature? Generating heat is easy; dictating and regulating a specific temperature is the hard part. ...
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42 views

Mux switching one leg of differential signal

I found the schematic below for a muxed thermocouple circuit from this web page. This circuit uses a mux to switch just one leg of the thermocouples. While I am sure that this works fine I have a ...
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99 views

Voltage of thermocouple

As we know, when we use a thermocouple, we measure mV value. This is what I wonder. Why we measure voltage not current? Like voltage, I think the current of T/C is proportional to temperature too.
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406 views

Splitting/y'ing a thermocouple amongst 2+ inputs

The system in question has just one type K thermocouple. Is it a bad practice to Y a thermocouple into 2+ thermocouple inputs? For example, Y a thermocouple into: DAC thermocouple input card Limit ...
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115 views

Can LM35 temperature sensor be used to measure temperatures in bone in an in vitro setting? are they comparable to K type thermocouples?

I belong to the medical field. I have zero knowledge about electronics. For my thesis, where I will be measuring temperature within the bone during drilling, I am required to use a temperature sensor ...
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67 views

infrared and K-Type temperature sensors badly disagree [closed]

They are both cheap. There is a piece of PCB balanced on top of the K-type thermocouple's probe; there is also a red laser light from the infrared thermometer right in the middle of the same PCB where ...
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409 views

Soldering iron thermocouple measurement HELP

I'm working on a relatively simple soldering iron circuit. I'm using a T12 tip, which consists of a resistor and thermocouple in series. I'm driving the gate of the N channel mosfet with 20V via a ...
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496 views

Current from thermocouple (T/C)

Studying thermocouples (T/C), I have a question regarding the output. Generally speaking, in the case of T/C, we measure the thermoelectric voltage in millivolts. Why do we calculate not current, but ...
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130 views

Why does a thermocouple have two outputs (V+ and V-)?

Does that mean that there is two different voltages? The potential is used to determine the temperature. (?) I understand it's the seebeck effect dictates how the thermocouple works. Apologies ...
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MAX 6675 module not working shows 0 degrees celsious 0 fahrenheit

This isn't a problem, rather a solution. I have a MAX 6675 module connected to an stm32 development board which at the beggining it worked perfectly and suddenly, it just showed 0C and 32F. Always ...
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106 views

Need help troubleshooting after short-circuit, with heaters and thermocouples

There was a short circuit in one of the furnace that I designed. Description of the furnace and its components: The furnace is a copper tube, with 1/2 inch thickness, and 10 equally spaced 1/4 inch ...
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81 views

Error deriving temperature from thermocouple amplifier

I'm using a K-type thermocouple to read the temperature of a 3D printer hot-end. To amplify the thermocouple voltage I am using the Analog Devices AD8495 chip. This chip is mounted on a custom-made ...
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1answer
59 views

Thermocouple amplification configuration

I am relatively new to thermocouples. We are wanting to get the temperature of fire ball blast. We are using a Type-K thermocouple and a Phoenix Contact mini signal conditioner to amplify the signal. ...
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57 views

Thermocouple chip & CJC compensation under 0°C

We are currently designing a "conditioning" module that takes a couple of sensors (T°, Pressure but also via digital bus) and repeats over CAN / also outputs them in nice and clean analog signals (0-...
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1k views

K-Type Thermocouple, Instrumentation Op-Amp and Arduino

I am Trying to read in a K-Type Thermocouple to a 0-5V Arduino Uno. I Can read my Thermocouple directly using a Fluke meter on temperature setting giving me the correct value of 21°C, but when I ...
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387 views

Connecting K-Type Thermocouple wires to a data logger with a male and female plug

I'm trying to setup a temperature data logger using Graphtec GL240. I will be using K-type thermocouples for the logger. I want to run short length of k type cables from the logger to a female K type ...
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59 views

How to convert a temperature readout to a K-type thermocouple voltage? (reverse thermocouple converter)

I am working with a commercial heating controller device which takes in a thermocouple input in order to regulate the heating temperature. However, in some cases, the thermocouple junction just isn't ...
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150 views

Connect Thick thermocouple wire to Type K Connector

I have purchased a high-temperature K type thermocouple that has two 14 gauge solid leads. I wanted to know what the best way to go about connecting these leads to a type K connector would be.
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120 views

Can I connect Analog and Digital Voltage Source together?

Is it bad if I connect the A_VDD and D_VDD Pins together if I want to use the same voltage? Or maybe I should ask: Why can I hook up different voltages other than galvanic decoupling? This is the IC I ...
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318 views

pass thermocouple K type through d-sub and circuit box - what might be error?

What might be temp error if I'll pass my TC through simple d-sub (green & pink) and from my circuit box (blue) to destination device (yellow) I want to use copper wire, wire lenght between them ...
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95 views

k-type thermocouple with latency

Bought from here I have tried the magnet trick and it does not stick to either of the two wires of this TC. More so, screwing it inside an oven and turning the temperature up does produce some micro ...