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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62 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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768 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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54 views

Thermopile temperature sensor

I am using an MRT511 thermopile temperature sensor. The datasheet shows a R-T table. I measured the resistance between 2nd and 4th pin of the sensor and voltage by using a voltage divider circuit. It ...
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31 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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51 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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54 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
107 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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34 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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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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56 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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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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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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62 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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120 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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178 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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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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62 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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80 views

Inconsisent SPI data transfer with MAX31856

I am using an Arduino to communicate with a MAX31856 on a custom-built PCB. The Arduino is loaded with this library, which seems to be working correctly. Unfortunately the data being read by the ...
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2answers
57 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
43 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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41 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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428 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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131 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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44 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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56 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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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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164 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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56 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 ...
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Can I amplify a thermocouple Signal with the GS8332-SR OP-Amp?

Theremocouples have a very small voltage of around 0.4mV/10C. K Type Thermocouple Voltage Table I want to amplify that signal so I can read it with an ADC on my Arduino Microcontroller. The Voltage ...
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245 views

Effect of wire gauge change on thermocouple measurement

I'm working on attaching to a thermocouple harness that had six 16AWG chromel wires and one 12AWG Alumel. The alumel would T off with each of the chromel wires to make a pairing and so the common was ...
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280 views

Negative voltage at the output of non-inverting opamp

I want to amplify the output voltage of a thermocouple by using a two-stage operational amplifier but the output that I get is a negative voltage at or below room temperature(<=30 degree Celsius). ...
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65 views

Reading T/C voltage when Heater is present in series

I am trying to read the thermocouple voltage of a Hakko T12 tip which has the heating element present in series with the thermocouple. The problem is that 24V DC will be present on T+/T- of the ...
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316 views

How to Amplify Thermocouples (and DC sensors between 1mV and 1µV DC)?

This is a bad idea, I know Here's what I know about amplifying really tiny DC voltages: it's impractical to build your own for production there's going to be noise the signal is relative to the cold ...
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52 views

Can a grounded thermocouple cause GFCI to trip?

I noticed the tip of my soldering iron is case grounded. I understand the GFCI compares voltages and trips if there is a difference (in the millivolt range). If the thermocouple generates a small ...
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278 views

How do I determine whether a sensor is a thermocouple or a thermistor?

Is there any nondestructive way to determine wether a soldering iron uses a thermocouple or a thermistor? The documentation on the iron claims it is a PTC ceramic heater. Some manufacturers mention ...
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232 views

Can resistors be used to bring a heating element within range?

I have a replacement 24V/60W desoldering gun I would like to modify for use on my Aoyue Int958A+ soldering station. My 968A+ has a smoke absorber which has enough suction to double as a solder vacuum. ...
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Why do heaters vary widely in resistance even though they have similar power requirements?

I have a soldering station equipped with a 24V/60W soldering iron. Its heating element (pins 1-2) resistance measures around 50 ohms. The resistance of the thermocouple (pins 4-5) measures around 2 ...
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112 views

Erratic behavior of thermocouple input

I am reading temperature from a K thermocouple on a PLC which is then forwarded to a trending software to see the data on a graph. The thermocouple is in a water trough/reservoir. In fact, there are 3 ...
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86 views

4-20mA current loop - transmit sensor reading

I am working on design loop current transmitter- to transmit reading value from thermocouple sensor using below design. I measured co-junction temperature using NTC instead of RTD. During applying ...
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Perdiodic thermocouple signal buffer for hot tub

I'm not exactly sure what to call this technically, which has hindered my ability to research solutions, so I think best just to describe the challenge and see what we can figure out. I have an older ...
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4answers
176 views

Differential amplifier with common voltage far above the rail?

I have a thermocouple with one end connected to +24V. I want to be able to read the voltage (-5mV - +20mV) on it using a 3.3V ADC. The most reasonable solution I see is lowering the voltages using ...
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851 views

High resolution ADC vs amplifiers

I have started a design for work where I want to interface some sensors, (strain gauge, bridge, thermocouple, low voltage stuff) to a national instruments sbRIO card. This card has analog inputs built ...
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2answers
45 views

Supplying two temp controllers with a single element thermocouple

I am installing a process temperature controller and an overtemp controller for a heater bundle. Normally I would just install two thermocouples, one for each controller. But space is limited and I ...
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86 views

Will thermocouples sharing a common wire create inaccuracies during measurement?

Specifically, I've been working with pre-existing temperature cables which are T-type thermocouples which share the same Constantan wire. My question is if one of the thermocouple junctions is heated ...
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56 views

Selecting temperature probe for home use with long cable / low power [closed]

I would like to monitor the temperature outside my home. The sensor has to be located at least 20m cable length from the display unit. Whole system should be powered by a battery (doesn't matter which)...
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Modelling a temperature measurement system

The accuracy of a measurement system can be significantly reduced by loading effects in the system. A thermocouple is used together with an indicator to measure temperatures. The thermocouple has a ...
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How to read a thermocouple chart

Studying for the PE exam, everything seems to be a breeze, but I cannot for the life of me read a TC chart. Specifically, I have a sample problem in a study guide where the measured voltage is 21....
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248 views

What options are available for measuring grounded thermocouples?

I'm using 4 MAX31855 ICs to measure 4 K-type thermocouples and realized that 2 of my thermocouples have grounded junctions; I simultaneously also realized the MAX31855 is stated to not support ...
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3answers
407 views

Instrumentation amplifier output stuck high

I tried to design an inamp for a K-type thermocouple. In theory the gain of this amp should be 250 (close enough to 10 mV/K), and if my understanding of instrumentation amplifiers is correct the ...