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.

Filter by
Sorted by
Tagged with
9 votes
3 answers
952 views

Why does a Pt100 RTD fail after immersion in thermally conductive and electrically isolating paste?

I currently have a Class A Pt100 RTD connected via an Adafruit RTD amplifier to an Arduino using SPI. It has good thermal contact with the warm surface after immersion in a thermally conductive (and ...
user avatar
  • 105
0 votes
3 answers
58 views

RTD Simulator vs Resistors

I want to use an RTD simulator for my project to simulate the PT100 0r PT1000. But I ant to learn that is it really necessary to use a simulator? Of course I can use some different kind of resistors ...
user avatar
  • 3
0 votes
1 answer
110 views

MAX31865AAP+ PT100 Excitation Current Problem

I have a PT100 and I'm using MAX31865AAP+ for RTD-to-Digital Converter. But I have a problem and I don't understand why this is. I use 400R REF resistor for PT100 and the reference resistor current is ...
user avatar
  • 3
1 vote
1 answer
98 views

MAX31865 and MAX31855 Completely not Working

I am beginner in Electronics. While working with MAX31865 and MAX31855 Modules it was working perfectly, but after designing custom PCB based on modules its not working. RTD shows -242C and 982C ...
user avatar
1 vote
2 answers
72 views

RTD lead-wire composition: choosing between silver or gold-plated nickel wires

I am selecting a platinum thin-film RTD for a sensing application. I have settled upon TE Connectivity's PTF Family. Within this family, there are two different options for lead-wire composition: ...
user avatar
  • 245
2 votes
0 answers
62 views

RTDs: Resistive Divider or Wheatstone bridge

I've inherited a PCB design in which the circuit for reading a 1k 2-wire RTD sensor is a simple resistive divider. The R_rtd is the pulldown part of the divider. The voltage of the divider is read ...
user avatar
0 votes
1 answer
72 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 ...
user avatar
  • 61
0 votes
2 answers
168 views

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 ...
user avatar
  • 1
4 votes
1 answer
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 (...
user avatar
0 votes
1 answer
124 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 ...
user avatar
0 votes
1 answer
37 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 ...
user avatar
8 votes
5 answers
893 views

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, ...
user avatar
  • 161
3 votes
3 answers
530 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 ...
user avatar
0 votes
1 answer
150 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 ...
user avatar
  • 2,524
0 votes
1 answer
67 views

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 ...
user avatar
1 vote
1 answer
118 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 ...
user avatar
1 vote
2 answers
93 views

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?
user avatar
  • 21
1 vote
3 answers
126 views

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 ...
user avatar
1 vote
2 answers
321 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 ...
user avatar
  • 245
1 vote
1 answer
38 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 ...
user avatar
0 votes
2 answers
1k views

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 ...
user avatar
0 votes
2 answers
88 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 ...
user avatar
0 votes
3 answers
660 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 ...
user avatar
  • 317
1 vote
0 answers
169 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 ...
user avatar
0 votes
1 answer
760 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 ...
user avatar
  • 1,303
0 votes
1 answer
156 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 ...
user avatar
0 votes
1 answer
179 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 ...
user avatar
0 votes
1 answer
257 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 (...
user avatar
0 votes
2 answers
220 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 ...
user avatar
0 votes
1 answer
232 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 ...
user avatar
  • 337
1 vote
1 answer
532 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 ...
user avatar
1 vote
1 answer
209 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 ...
user avatar
  • 37
0 votes
1 answer
37 views

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 ...
user avatar
  • 1
0 votes
2 answers
781 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 ...
user avatar
  • 1
0 votes
3 answers
917 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 ...
user avatar
  • 1,035
1 vote
3 answers
220 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 ...
user avatar
0 votes
1 answer
344 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 ...
user avatar
0 votes
4 answers
2k views

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. ...
user avatar
  • 263
2 votes
4 answers
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 ...
user avatar
  • 159
0 votes
2 answers
359 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). ...
user avatar
  • 249
0 votes
2 answers
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 ...
user avatar
  • 249
0 votes
1 answer
89 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, ...
user avatar
  • 569
4 votes
1 answer
905 views

How do Resistance temperature detectors (RTD) work?

What is the difference between RTD and Thermocouples ?
user avatar
1 vote
3 answers
315 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 ...
user avatar
1 vote
2 answers
2k views

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's on it. From those six I use five of them. The device reads out the ...
user avatar
  • 23
2 votes
6 answers
795 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 ...
user avatar
  • 131
4 votes
2 answers
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 ...
user avatar
2 votes
3 answers
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 ...
user avatar
  • 21
1 vote
1 answer
984 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 ...
user avatar
  • 3,204
1 vote
3 answers
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.
user avatar