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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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DAQ that records temperature using laser / infrared non contact thermocouple to measure temperature over time

I have a usb-2001-TC Thermocouple Device that supports J, K, R, S, T, N, E, and B type thermocouples see link and a Digital Infrared Thermometer Laser see link but as you know these can't be connected ...
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58 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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1answer
27 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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1answer
33 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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1answer
46 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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49 views

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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1answer
41 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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68 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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24 views

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
126 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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621 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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34 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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1answer
67 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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2answers
50 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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2answers
65 views

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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126 views

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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1answer
86 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
187 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 ...
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1answer
136 views

What can you tell about our circuit diagram? Any suggestions?

This is our circuit for our research which is the conversion of heat to electricity. The TEG module will convert the heat to direct current. It will give energy to the voltage booster moduleto and the ...
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1answer
44 views

ads1232 SCLK pin timing

I'm working on reading analog voltage from type S thermocouple which is approx 10 microvolts per degree Celsius using ADS1232 TI converter. according to the device datasheet page 19, serial clock ...
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3answers
337 views

How to use LM35's temperature as cold junction for K type thermocouple?

I have been trying to built an thermocouple base temperature monitoring system which can measure negative temperatures (say about -150 C). I previously have used max6675 but later on I found out it ...
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4answers
491 views

Can I cut off a thermocouple's metal head?

I want to attach a thermocouple to my 40Watt soldering iron in order to make it temperature controlled. The thermocouple I'm going to buy is a K type MAX6675 thermocouple that looks like this: But ...
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4answers
823 views

Why does a thermocouple circuit need to have minimal current flowing through it?

I was reading on this website that it is imperative that current in a thermocouple circuit be kept as low as possible for good measurement accuracy Why is this the case? Also, if one makes it so ...
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79 views

Peltier Module constant time and thermal Load

Hi everyone I am new to this forum. I am doing a project where I need to control one of the sides temperature of a Peltier device against human skin. So one side is in contact with the skin, and the ...
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1answer
240 views

Thermocouple noise causing spurious reading with SSR

I have a thermocouple PID SSR heater as shown, based on the MAX31855 ( datasheet ). I get spurious readings when the arduino is plugged into my laptop, my laptop is plugged in to its charger, and the ...
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58 views

Accidentally misconfigured T type thermocouples as J. How do I convert my data?

I was running a test between -70C and 70C using T type thermocouples but misconfigured it on my DAQ(keysight) to J. Is there a way to convert the data I gathered to the correct settings?
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74 views

How can I tell from a datasheet if a thermocouple amplifier IC will work with a grounded thermocouple?

There are several different solution available for thermocouple amplification such as the MAX31856, AD8495, and LTC2983. Some of these support grounded thermocouples (AD8495) and some don't (MAX31856)....
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2answers
205 views

Where is the ground reference when using a thermocouple?

I am using a MAX31856 to read thermocouple voltages. I have an ADG707 differential multiplexer feeding the MAX31856 from various ungrounded thermocouple probes (see diagram below). I am using the ...
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1answer
202 views

Does the AD8495 thermocouple amplifier allow for grounded thermocouple probes?

I recently purchased a MAX31856 thermocouple-to-digital chip for a project. However, I discovered that the chip does not support grounded thermocouples. I am looking for an alternative and the AD8495 ...
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2answers
109 views

Does changing wire gauge change output of a thermocouple?

So I've been experimenting creating thermocouples with copper and constantan wire, just by twisting them together at one end and heating the junction with a candle and using a voltmeter to measure the ...
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3answers
122 views

How to calculate\estimate thermocopule junction of a solder junction between a PCB and a component

Thermal junctions between two dissimilar metals on a PCB can create voltages. How do I estimate or bound (by estimating a max voltage via a max temperature) the thermocouple effect on a pcb? Most ...
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1answer
71 views

Thermocouple with Difference amplifier

I just able to find EMF=4017 µV. Then, how can I find R1, R2, R3 and R4 with just one equation? Is my answer correct ?
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1answer
162 views

µC (Arduino) and Dealing with thermocouple noise

We've recently used an arduino along with a MAX31856 breakout board to measure some type-J Thermocouple temperature and then replicate it as a KTY xxx through a digital pot (MCP4261). So all this ...
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211 views

JBC soldering iron cartridge thermocouple type

I have recently bought a T245-B soldering iron handle and a C245064 cartridge. These are both made by JBC. I have tried to find the thermocouple type online but have had a range of answers from type k ...
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1answer
109 views

Does the MAX31855 thermocouple converter output accurate temperature values?

I'm trying to figure out why my MAX31855 thermocouple converter appears to be outputting inaccurate temperature data. I'm curious if this is due to non-linearity in the converter. Link to data sheet: ...
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1answer
79 views

Input voltage limits of AD8495 (thermocouple amplifier) vs supply voltage

I'm working on an android multigauge for cars based of a pic microcontroller. Some inputs from sensors are not fed by my circuit so after stumbling upon this thread: http://www.microchip.com/forums/...
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1answer
430 views

How do Resistance temperature detectors (RTD) work?

What is the difference between RTD and Thermocouples ?
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1answer
111 views

Toaster Oven Reflow Thermocouple Grounding

In order to create a homeade reflow solder oven, I am using a K-type thermocouple connected through a MAX6675 module and reading it with an ATMEGA8 microcontroller. When the oven is disconnected from ...
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1answer
556 views

Thermocouple Amplifier Circuit Question (OP AMP Bias Current Path)

This is 2 Diffrent Cold Junction Compensated Thermocouple Amplifier Circuit. I just don't understand why needs 1.5MOhm(OP291 Figure 70.), R4 6.04k(OPA335 FIGURE 3.) and How to Calculator Resistor ...
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2answers
153 views

Can I multiplex a thermocouple (using a MPC507) without losing significant accuracy?

I would like to reduce the number of thermocouple to digital converters (MAX31856) needed on my board for the sake of space. One approach that I have considered is multiplexing the eight different ...
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2answers
120 views

Thermocouples - to determine temperature use equation or tables? [closed]

I am building a controller based around J-type thermocouples designed to go to 500 degC. To convert voltage to temperature I can either use a linear equation, or table lookup. The lookup is, I assume, ...
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2answers
277 views

Thermopile temperature sensor (non-contact) amplifier design

I'm trying to design a circuit that amplifies a group of thermopile sensors (datasheet) from a mV reading to a V reading (gain ca. 100-1000) for a uC's ADC input. These sensors have a typical ...
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0answers
39 views

I need to measure liquid temperature down to -80C [duplicate]

Building a device that will sit inside a liquid that will be a max of -80C and trying to figure out what my options are for measuring the temperature. I was thinking a thermocouple but not sure if ...
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2answers
875 views

Thermocouple power/current production efficiency

I know that thermocouples produce electric current when there is a temperature difference between their two ends. This current is directly proportional to the temperature difference. I also understand ...
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0answers
29 views

MAX31855K reported temp dropping when AC current applied at ktype thermocouple location

I'm trying to use a Raspberry Pi, MAX31855K thermocouple amplifier, and solid state relay to control an espresso machine's boiler using a PID. However I'm hitting a frustrating snag. I have ...
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1answer
476 views

Should the thermocouple wires be insulated against a metal shaft

I am working on a project where I am using Omega bare TC. Its just two wires welded at the tip. I am using MAX6675 coupled with an Arduino. Should one of the two leads be insulated? The bare ...
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1answer
129 views

Thermocouple differential output to thermocouple input

I have a controller with two k-type thermocouple inputs. I'd like to have one of those inputs be the difference between the two TCs. Since TCs are voltage devices, it looks like an opamp would be ...
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2answers
110 views

Op Amp Circuit help! [closed]

I am hoping you can help me. I am trying to design an op amp circuit that can read negative 2ma-20ma. We are trying to read a thermocouple and we have tried many variations of a simple circuit ...
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0answers
58 views

SPI not working without usb

I am trying to read a MAX31855K using SPI on a Teensy 3.2, and then send the data back over an Iridium modem connection. The setup is working fine when I have the teensy plugged into USB, but when ...
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3answers
906 views

Optimizing op-amp overload recovery behaviour

I'm measuring a thermocouple which connected series with a heating element. Heater is driven with PWM and when PWM is off-duty, a measurement is taken through output A0 using an ADC. Relevant parts ...