Showing posts with label Thermocouples-RTD. Show all posts
Showing posts with label Thermocouples-RTD. Show all posts

Friday, April 21, 2017

How does RTD Work

How Resistance temperature detector works?

Post by JG

The most popular RTD is PT-100, Platinum 100 Ohms, As all Metals have a Temperature Coefficient of Resistance. The Resistance of RTD increases with rise in temperature.

How does RTD Work

Even Copper wire can be used, but you need to have a very thin and long wire to make usable measurements.

Resistance: Temperature Coefficient - Since the electrical resistance of a conductor such as a copper wire is dependent upon collisional proccesses within the wire, the resistance could be expected to increase with temperature since there will be more collisions

Resistance thermometer - Wikipedia - . The RTD wire is a pure material, typically platinum, nickel, or copper. The material has an accurate resistance/temperature relationship which is used to provide an indication of temperature. As RTD elements are fragile, they are often housed in protective probes.

What are RTDs? - in the case of Platinum known variously as PRTs and PRT100s, are the most popular RTD type, nearly linear over a wide range of temperatures

What is a Resistance Temperature Detector (RTD)? - Most RTD elements consist of a length of fine coiled wire wrapped around a ceramic or glass core.
The material has a predictable change in resistance as the temperature changes; it is this predictable change that is used to determine temperature.

delabs
This is an answer of mine to an old post - 2006

Friday, March 17, 2017

How to Connect RTD to transmitter

Can you explain me were i have to conect the three cables of the PT100 in the Circuit RTD-Pt-100-Transmitter Circuit?

RTD PT100 Transmitter and Multiplexer

Comment from CV of Spain

You have a three wire RTD, there is also a 4 wire RTD type, This circuit can be used for both.

In the 3W RTD you have two wires coming from the same point (zero ohms between them) the third wire will be 100 ohms from these two. From the two wires that are at same point take one wire and give 1mA from Q3 + OUT. The other wire of the pair connect to input +..... input - can be connected to the 100E end.

How to Connect RTD to transmitter
delabs

So imagine that I have three wires one white and two blacks.

One black to +OUT 1ma
Other black to input-

And waht about the withe one that is the one that give me arround 100ohms??

Reply from CV

Black 1 - +Out 1mA
Black 2 - +Input
--------------
White goes to -Input

See NI Developer Zone - RTD Connections

delabs

Monday, January 09, 2017

Comparison of Thermocouple and RTD

message: what is the pros and cons of rtd,over thermocouple

Mail from MU

Read the pages in links below, that ought to clarify your doubts. Last edited February 16, 2007

Comparison of Thermocouple and RTD

RTD-TC-Compare
Comparison of Thermistors, Thermocouples and RTD's ... Unlike RTD's and thermistors thermocouples have plus and minus legs so polarity must be observed.
Comparision of Thermistors, Thermocouples and RTD's

Thermocouple - No resistance lead wire problems, Fastest response;  RTD - Most stable, accurate, Contamination resistant,; Thermistor - High output, fast, Point temperature sensing.
Watlow - Temperature Sensor Comparison Guide

Since thermocouples measure wide temperature ranges and are relatively rugged, they are very often used industrial and process applications where accuracy may be a less important factor.
RTD vs. Thermocouple comparison chart

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