Why is it called a thermometer?
Why is it called a thermometer?
The word thermometer (in its French form) first appeared in 1624 in La Récréation Mathématique by J. Leurechon, who describes one with a scale of 8 degrees. The word comes from the Greek words θερμός, thermos, meaning “hot” and μέτρον, metron, meaning “measure”.
What does the Greek root word meter mean?
measure
Why is was alcohol used in thermometers?
Unlike the mercury-in-glass thermometer, the contents of an alcohol thermometer are less toxic and will evaporate quickly. The ethanol version is the most widely used due to the low cost and relatively low hazard posed by the liquid in case of breakage.
Can we use alcohol in thermometer?
Alcohol thermometers are used rather than mercury thermometers in very cold regions because alcohol has a lower freezing point than mercury. Pure ethanol freezes at -115 degrees C, while mercury freezes at -38 degrees C. Thermometers rely upon thermal expansion of the liquid in a bulb at the base of a thin glass tube.
Is a mercury thermometer better than the alcohol based thermometer?
It is more durable than alcohol thermometer because mercury does not evaporate easily. It is smaller in size as compared to alcohol one. Mercury does not wet the wall of the thermometer, which means that results can be highly accurate.
Are alcohol thermometers more accurate?
Alcohol thermometers are also inexpensive and durable. They are typically not as accurate as mercury thermometers because of the alcohol’s susceptibility to evaporation, polymerization potential and capillary separation. Their primary advantage is safety to humans and the environment.
Which thermometer is more sensitive alcohol or mercury?
There is a technical reason for using mercury in clinical thermometers. Mercury has a greater coefficient of thermal expansion than alcohol. This means a column of mercury will expand and rise more than a column of alcohol for the same temperature change. As a result, you can get finer readings with mercury.
Why is alcohol preferred over mercury in thermometers?
Advantages of using alcohol over mercury as thermometric liquid are: i) Alcohol has greater value of temperature coefficient of expansion than mercury. ii) it’s freezing point is below –100°C. Thus, alcohol thermometer is more sensitive than mercury thermometer and can be used to measure the temperature below –40°C.
Are mercury thermometers more accurate?
But mercury thermometers also have real advantages over the alternatives. They’re often cheaper and more accurate, especially at higher temperatures. And unlike one common alternative, electronic thermometers, they’re self-contained (no wires sticking out) and require no power.
Does mercury boil faster than alcohol?
It is taken to be 1000C. The temperature of steam is used since impurities do not affect its temperature but will raise the boiling point of water….THERMAL EXPANSION.
| Mercury | Alcohol |
|---|---|
| Has high b.p, 3570C | Has low b.p, 780C |
| Relatively high freezing point, -390C | Low freezing point, -1150C |
| Good thermal conductor | Poor thermal conductor |
What are the disadvantages of mercury?
The Weaknesses or the disadvantages of Mercury:
- It cannot measure very low temperature, because its freezing point is high (-40ºC)
- Mercury is poisonous, so it harmful if its tube is broken.
- Its price is very high.
- display is harder to read.
- cannot be used for thermograph.
- slow response.
- fragile.
What is the advantage and disadvantage of mercury?
A thermometer comparison
| advantages | disadvantages |
|---|---|
| Mercury thermometer | |
| cheap | display is harder to read |
| durable | does not work below -39 C (Hg freezing pount) |
| accurate | cannot be used for thermograph |
What are the advantages and disadvantages of alcohol and mercury thermometers?
Difference between Advantages And Disadvantages Of Mercury And Alcohol Thermometer
| Advantages | Disadvantages |
|---|---|
| lower freezing point (-1140C) | less durable (alcohol evaporates) |
| larger coefficient of expansion | alcohol can polymerise |
| less hazardous | fluid loss by evaporation hard to avoid |
| lower boiling point (600C) |
What are the advantages of mercury in thermometer?
Advantages of mercury:
- Mercury thermometers give accurate readings.
- Quick reaction to changes of temperatures because metal is a good heat conductor.
- Mercury has a very low saturation vapor pressure.
- Possible to measure higher temperatures as in cooking.
- Same expansion coefficient at all temperatures.
Is mercury still used in thermometers?
Although mercury thermometers have been mostly phased out of daily home use, the tool, which was invented in the 1700s by Gabriel Daniel Fahrenheit, remains a standard measuring device for many industries, including regulating the temperature of a chemical concoction being made in an industrial lab, and monitoring the …
Why are thermometers preferred to mercury thermometers?
Answer. the temperature measured in the digital thermometer are more exact than the temperature measured in the mercury thermometer. and also if mercury thermometer breaks then mercury which is very toxic comes out and may create problems.
Are thermocouples more accurate than thermometers?
The main difference between Thermocouple and Thermometer is that the Thermocouple is a thermoelectric device and Thermometer is a device to measure temperature. The main limitation with thermocouples is accuracy; system errors of less than one degree Celsius (°C) can be difficult to achieve.
Which temperature sensor is best?
An NTC thermistor is able to achieve the highest accuracy of the basic sensor types within the -50 °C to 250 °C range. Accuracy ranges from 0.05 to 1.5 with high long-term stability, depending upon the type of sensor and packaging used. NTC thermistors also offer superior responsiveness, on the order 0.12 to 10 s.
Which thermocouple type has the greatest sensitivity?
Type K. Type K (chromel–alumel) is the most common general-purpose thermocouple with a sensitivity of approximately 41 µV/°C.
Which thermocouple is more accurate?
Accuracy: RTDs are generally more accurate than thermocouples. RTDs have typically an accuracy of 0.1°C, compared to 1°C for most. However, some thermocouple models can match RTD accuracy.
How do you know if a thermocouple is accurate?
To determine the initial accuracy of a thermocouple, you simply determine the greater of the two tolerances given. Note that standard and special tolerances for thermocouples are determined using the same method. Multiply 300°C by ±0.0075 which gives ±2.25°C.
Why are thermocouples inaccurate?
Because a thermocouple measures temperature differentials, any temperature fluctuations around the reference junction (cold junction), which has the known temperature, result in an erroneous temperature reading. Simple insulation can also protect the junctions from extreme temperatures.
What is the difference between thermocouples and RTD?
Key Differences Between RTD and Thermocouple. An RTD utilizes the change in resistance of the metal to predict the change in temperature. While thermocouple is a thermoelectric sensor that uses the change in voltage/ emf to get the change in the temperature. RTD generally operates in the range between -200 to 600° C.
What is difference between RTD and PT100?
There is no difference a PT100 is a version of a RTD (resistance temperature detector). What is an RTD? A resistance temperature detector, also known as an RTD or resistance thermometer, is a type of temperature sensor.
What is a PT100?
Pt100 sensors are the most common type of platinum resistance thermometer. Pt refers to that the sensor is made from Platinum (Pt). 100 refers to that at 0°C sensor has a resistance of 100 ohms (Ω). A resistance thermometer is a type of temperature sensor.
Where is RTD used?
Sometimes referred to as resistance thermometers, RTDs are commonly used in laboratory and industrial applications because they provide accurate, reliable measurements across a wide temperature range.
Are thermocouples AC or DC?
Being the thermocouple voltage a DC signal, removal of AC noise through filtering is beneficial; furthermore the thermocouples produce voltage of few tens of mV and for this reason amplification is required.
What is the most common type of RTD?
Platinum RTDs
What is RTD and how it works?
An RTD works by using a basic principle; as the temperature of a metal increases, so does the resistance to the flow of electricity. An electrical current is passed through the sensor, the resistance element is used to measure the resistance of the current being passed through it.