what is meant by the change go temperature of 1 degree celcius on the scale of a plantinum resistance thermometer
explain what is by a change in temperature of 1 on the scale of a platinum resistance thermometer
The length and diameter of the platinum wire used in a thermometer are often chosen so that the resistance of the device at around 0 ºC is 100 ohms. Such a sensor is a called a PT100 sensor, and its resistance changes by approximately 0.4 ohms per degree Celsius. Using a typical 1 mA measuring current, at around 0 ºC a PT100 sensor would have a voltage drop of around 100 mV across its terminals and this would change by approximately 0.4 mV per degree Celsius, which thus makes sensitive thermometry available to anyone with a high resolution voltmeter or resistance bridge. In many instruments the measurement is converted so that the reading is directly in temperature.
Explain what is meant by by a change in temperature of 1 degree Celsius on the scale of a platinum resistance thermometer
A change in temperature of 1 degree Celsius on the scale of a platinum resistance thermometer refers to the difference in resistance exhibited by the thermometer when the temperature increases or decreases by 1 degree Celsius.
Platinum resistance thermometers work on the principle that the electrical resistance of platinum wire changes with temperature. As the temperature increases, the resistance of the platinum wire also increases, and vice versa.
To find out how the temperature change of 1 degree Celsius affects the resistance, you need to determine the sensitivity or temperature coefficient of the platinum resistance thermometer. The sensitivity, generally denoted as α (alpha), represents the change in resistance per degree Celsius.
The temperature coefficient of platinum varies slightly depending on the specific platinum alloy and the temperature range of interest. However, a commonly used value is around 0.00385 Ω/Ω/°C, which means that for every degree Celsius change in temperature, the resistance of the platinum wire will change by approximately 0.00385 times its original value.
To calculate the change in resistance, you can use the equation:
ΔR = R * α * ΔT
Where:
ΔR is the change in resistance,
R is the initial resistance at a specific temperature,
α is the temperature coefficient (0.00385 Ω/Ω/°C for platinum),
ΔT is the change in temperature.
For example, if the initial resistance (R) is 100 Ω and the change in temperature (ΔT) is 1 degree Celsius, using the temperature coefficient of 0.00385 Ω/Ω/°C,
ΔR = 100 * 0.00385 * 1 = 0.385 Ω
Therefore, a change in temperature of 1 degree Celsius on the scale of a platinum resistance thermometer with a sensitivity of 0.00385 Ω/Ω/°C would result in a change of approximately 0.385 Ω in resistance.