Questions tagged [rtd]

Resistance Temperature Detector (RTD). An RTD sensing element usually consists of a metal filament, which is coiled on a mandrel or etched on a substrate. The RTD element is made from a pure material, typically platinum, nickel or copper. The material has a predictable change in resistance as the temperature changes; it is this predictable change that is used to determine temperature.

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47 views

RTD non-ratiometric ADC measurement

I am thinking of replacing standard ratiometric RTD measurement (of temperature) with two sequential measurements. The reason is I have to use an ADC already on the PCB and cannot replace its ...
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LTspice: Can I simulate current generated heat?

I'm simulating a simple circuit with a resistance temperature detector. I want to know if it is possible to simulate the small change in the resistance as the current flowing through the resistor ...
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1k views

Why does a resistor have this value in a circuit with an operational amplifier?

I'm analyzing this circuit to condition a PT100. I clearly understand what the circuit does, but the current flowing through R7 is very small and negligible. So in theory it could be any value (...
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61 views

3-wire RTD measurement circuit

I'm searching for some simple 3-wire RTD sensor to be measured using an ADC. I found some options, but I'm kinda confused with how does they works and which one is the best. First, there is the ...
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36 views

RTD reads differently with different monitors

I have an RTD that I am reading with a Jenco 77A 4-20mA converter and a reliable 4-20mA supply/display. When I turn on a nearby AC electric motor, the indicated temperature jumps 50°C (which is ...
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Is it normal to have this much fluctuation in an RTD measurment in boiling liquid?

I'm using a MAX31865 RTD measurement IC, and a standard PT100 RTD to measure maple syrup temperature as it's boiling (219 degF). At ambient, the temperature measurement is reasonably stable. But, ...
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412 views

Why does an RTD sensor circuit use a reference resistor that is 4x the RTD value?

I'm using an Adafruit MAX31865 board to measure the resistance of a PT1000 RTD. The board comes with a 4300-Ohm resistor. I'm trying to model the amount of noise (in degC/sqrt(Hz)) that I expect out ...
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80 views

pt100 RTD transmitters not working - two in a row - am I doing something wrong?

I just tried to use two different ones of these RTD transmitters with a pt100 probe (3 wire) with no success. I am connecting the transmitter directly to a 4-20mA input on a PLC, as shown in the ...
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RTD with a +/- 0.01 oC from its normal set value (78.37oC)

I am doing an assignement and have been asked to find a TMS for a whiskey distillary and I cannot find a suitable RTD. The parameters are that it needs to have a T range between 0 and 120 degrees ...
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1answer
87 views

PT100 temperature sensor: meaning of "measuring current" specification

I'm measuring temperature using a PT100 temperature sensor on a Wheatstone bridge. As I'm working on a battery powered application, I'm choosing the resistors in the bridge so that only a small ...
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Isolated RTD sensor

I need to read a Heatsink temperature with 5KV isolation. how is it possible? are there isolated temperature sensors ? or shall I design a board for it to isolate the output signals?
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Purpose of capacitors connected to both inputs of Op-Amp

What is the purpose of the capacitors in the following circuit? Using Ohm's law : V+ = I * RTD V- = I * R3 and also : Vout = G * (V+ - V-) => Vout = G*I(RTD - R3) The circuit is used to measure ...
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259 views

Sharing a single ground wire across multiple RTDs

Consider the following, simplified schematic for a single, two-wire RTD sensor: simulate this circuit – Schematic created using CircuitLab The two wires from the RTD sensor plug into pins 1 ...
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1answer
36 views

How to use a power meter to measure irradiance?

I have got a Zes Zimmer LMG95 power meter and an RS-ID-5 Fraunhofer ISE WPVS reference cell. The LMG95 has got simultaneous voltage and current measurement and can do custom calculations. The WPVS ...
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Working of INA826 instrumentation amplifier for Pt100 RTD

The schematic below contains an INA826 used to amplify the resistance of the Pt100 RTD across J1. Gain is set to 10 through the 5.49K ohm resistor. Is this ciruit amplifying only the voltage across ...
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79 views

What is the correct configuration for 3-wire RTDs connected to an ADAM 6015 module?

I have connected four RTDs by wire (via a 12 pin cable). The common wires of all four RTDs go through only two of the wires in the cable. After soldering those wires together and connecting them to ...
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516 views

Why is there a negative value on the scada when the analog input wire is disconnected from a field instrument?

I'm an apprentice electrician at an fmcg company. I've been seeing a trend recently, at the plant, where the scada actually reads a negative value instead of zero when a field device such as a ...
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0answers
138 views

What causes long-term RTD reading drifts?

I am working with a controller that was designed to read multiple types of inputs including 3 wire RTD signals. In some cases, we have observed the controller suddenly spike up +15 degrees and ...
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1answer
676 views

How are and what are the sources coupled to a 3-wire RTD leads? [duplicate]

I can understand two or four wire connection for RTDs. But I don't get where they apply voltage or current and how they measure the resistor values for 3-wire connection: Here is a page about these ...
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141 views

ITS-90 Tempature coefficents for a standard PT100 385 RTD

I'm currently using the ITS-90 formula to convert a resistance of an RTD to a temperature. I got the coefficients from the manufacturers calibration sheet. The problem is I have another probe that I ...
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1answer
144 views

PT100 - 39250 Cubic fit formula

I'm currently using a cubic fit formula I found online to derive the temperature of a PT100/385 RTD using resistance. The formula is -247.29 + 2.3992*R + 0.00063962 *R^2 + 0.0000010241 *R^3 where R is ...
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222 views

RTD circuit in industerial application

I'm trying to design RTD measuring for industrial use which has EMI/EMC/ESD. I have 3 wires input to the board. obviously 3 wires out of the board are going to 3-wire configuration PT1000 1- 3V3 (...
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171 views

RTD temperature measurement system resistance question

I am trying to produce a bridge circuit for the following temperature measurement system: Designed to measure temperatures between 0 C and 100 C with a high accuracy. When supplied with a 10 V ...
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1answer
192 views

Which temperature transducer has these characteristics?

The resistance temperature characteristics of a temperature transducer is show in the figure below, The transducer in question is which of the following? A) Nickel RTD B) NTC thermistor C) Platinum ...
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449 views

PT100 sensor for measuring liquid resin, fully submerged

Edited Link to Pt100 sensor (That's the best i could do) https://www.intech.co.nz/products/temperature/mrh.html Link to ESP8266 datasheet http://www.handsontec.com/pdf_learn/esp8266-V10.pdf ...
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191 views

Removing/Subtracting Lead Resistance Using Op Amp Circuit

I'm working with RTD sensor, and need to use Op Amp circuitry. Can someone explain to me how this Op Amp circuit work to remove the lead resistance? So that Rw1, Rw2, and Rw3 vanish, hence the ...
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MAX31865 RTD converter will it acccept only floating inputs?

We intend to use MAX31865 for measuring resistance values. Since MAX31865 is RTD to digital converter, kindly clarify whether the MAX31865 will accept only floating inputs or it can be used with ...
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1answer
696 views

Sallen-Key filter for PT100 RTD measurement

I am going to build temperature sensing system using PT100 sensor (and later Raspberry PI 3). I refer my work to Microchip note AN687 Precision Temperature-Sensing With RTD Circuits. On the page 4 is ...
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779 views

What does this resistor do in this RTD wheatstone bridge?

The question is in bold at the bottom, the following is background. I am going to measure air flow with a hot wire anemometer using the FS7 sensor from Innovative Sensor Technology (IST). They ...
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3answers
200 views

self-heating effect of dual PT100 temperature probe in a moving mass of water

I'm trying to know how much self-heating should I expect in these conditions: Temperature range: 0-45 C Using a 1050Ohm pullup resistor to feed each PT100 (2-wire configuration) with 5 volt ...
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1answer
313 views

MAX31865 - can I use a 150 ohm Rref?

I'm building a circuit for a home brewing application which will use the MAX31865 chip to read in temperatures of liquids from a RTD100 sensor. The chip does this by reading the current that flows ...
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RTD sensor circuit design

Design Criteria For a project I'm making I want to measure temperature using a 10 bit ADC on a MCU. I don't care for absolute accuracy but I would like precision down to around 1/10th of a degree C. ...
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5k views

How does 3-wire RTD or resistance measurement works in bridge of wheatstone?

I cannot understand how 3-wire measurement will improve the resistance measurement. They say that IF lead resistance \$ R_L \$ is the same, it will compensate. How can this happen? If bridge is ...
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327 views

Amplifier Circuit for Thermopile

I would like to build a circuit for reading temperature from a thermopile temperature sensor. I found this application reference for the circuit (page 6, Single power supply type with thermistor). ...
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1k views

How to calculate temperature resistance for Ni-RTD

I would like to build a circuit to read the signal from a thermopile temperature sensor which has build-in RTD temperature sensor for cold-junction compensation. The datasheet of the sensor is here. I ...
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82 views

Help on understanding how a strange RTD reading circuit works

I'm trying to figure out how this universal micro-plc works: https://www.maximintegrated.com/en/design/reference-design-center/system-board/6185.html It is supposed to read current, voltage, ...
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1answer
858 views

How do Resistance temperature detectors (RTD) work?

What is the difference between RTD and Thermocouples ?
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287 views

ADC variable reference voltage

I'm working on a design which must read temperature using RTD pt100 with at least 0.5 degree Celsius accuracy in the range -10 to 50 degrees . I want to use AD7705 ADC. my design looks like this. I ...
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Can long cables induce that much noise?

[UPDATE The problem is fixed and the results are in my answer below] I have designed a board with, among other things, six max31865 on it. From those six I use five of them. The device reads out ...
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769 views

Alternate way to read Resistance temperature detectors (RTDs) with Microcontroller

After reading many posts with difficulties reading a Resistive Temperature Detector (RTD) such as a PT-1000, NTC with e.g. an Arduino, I am wondering if a time based approach could be used: If I take ...
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2answers
1k views

Accurate yet relatively simple way to use RTD probes

I would like to build a reference thermometer for checking and maybe calibrating other sensors and I was planning to use 1/10 DIN RTD probe in order to do that. You can get such probes for ~$100 and ...
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3answers
3k views

How to choose the right amplifier for 100 Ohm RTD in 3 wire configuration?

I have been doing research for the past week on setting up a 100 Ohm Platinum RTD to work with labjack U3 LV (I have to use labjack). I know I have to start off with a wheatstone bridge, and use a ...
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1answer
905 views

Mapping a voltage range to whole ADC range using opamps

I want to use a micro for measuring temperature using PT-1000 sensor for range -40C to 150C. I have come up with these draft information, I appreciate it if a pro person can confirm my thoughts are OK ...
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9k views

What is the best sensor to use in a wearable device to monitor body temperature on a continuous basis: Thermistor, RTD or a semiconductor device? [closed]

Most wrist-worn wearables on the market today don’t seem to feature body temperature sensing which makes me wonder if all these sensors are inadequate in some ways.
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Precision voltage reference divider vs. constant current source to drive an RTD sensor

I need to measure temperature with an RTD between 0-300 C. I believe I have two options to make this work: A constant current source feeding the RTD A precision voltage reference and a resistor ...
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4answers
434 views

Tap into 4 wire RTD

Is there any way to tap into an existing 4 wire RTD without changing the resistance, and therefore changing the temp that the existing device will read? Here's the scenario. The device is a medical ...
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8answers
5k views

How to make a voltage controlled adjustable resistor?

I need it for simulating PT100, PT500, PT1000 RTDs, and thermistors in a temperature range of 0-200 °C. What I want to do is for example: enter 50 °C using a microcontroller, and through the DAC ...
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556 views

RC filter on ADC voltage reference pins: overkill or necessary?

I've been scouring the web for circuits suitable for reading RTDs using ADCs. In one document from TI it is suggested that the following filter be placed on the inputs of the voltage reference pins (...
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2answers
925 views

PT1000 2 wire probe. Can I add third wire?

I'v got 2 wire (81 cm) PT1000 probe which I want to utilize in a project. I would like to use current source and couple of opamps to make the measurement through ADC (uC) just like described here: ...
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632 views

RTD Sensor Datasheet Details

I need to read one type of rtd sensor using linked datasheet(page5) but as far as i know there must be a temperature vs resistance table. Am i missing something or given datas are enough to read ...