Temperature Measurement By 4 Wire RTD | Electrical Instruments Explained
The video gives brief explanation about 4 wire rtd , what is lead resistance and why 4 Wire RTD is more accurate than 2 Wire & 3 Wire RTD? In other videos of the channel , we explained lead wire compensation , brief explanation of 2 wire , 3 wire and 4 wire rdt.
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Why 4 Wire RTD is better than 2 Wire & 3 Wire RTD?
4 Wire RTD measures the temperature based on the voltage signal instead of resistance.
All 4 wire RTD has constant current source in series with the two lead wires. And voltage drop is measured across the another two lead wires of 4 wire RTD.
Ohm's law states that voltage drop across resistor is directly proportional to current and resistance value of that resistor.
V = IR
In 4 wire RTD we use constant current. So, current value will remain constant
or very less in this equation.
In other words, it does not affect voltage drop across resistor.
And the voltage will be generated based on the change in resistance, which depends on the measured temperature.
RTD resistance will change with temperature change, and it will change voltage drop across two lead
resistors. And temperature is measured based on voltage drop across two lead resistors.
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