What is the other way to measure L with a dial gauge for the expansion coefficient of a metal wire

Isn't it just to measure the volume, put it in the liquid at different temperatures, and use a measuring cylinder as fine as possible.

Measure the volume difference.

1. First of all, it is generally necessary to ensure that the steady state has been reached at the time of measurement.

If there is no steady state, there will be errors. Second, the measurement error of the temperature measuring element. Third, human error, such as the movement of the first can also cause errors.

The working principle is that the small linear movement of the measuring rod caused by the measured size is amplified by gear transmission and becomes the rotation of the pointer on the dial, so as to read the size of the measured size. The metal rod is elongated, that is, when the probe moves, the large watch hand turns exactly once. The large dial is evenly engraved with 200 grids, so that each small cell of the large dial represents mm.

When the large dial hand rotates one circle, the subdial hand follows the rotation of a small square, so one grid of the subdial represents the line displacement, and the subdial is evenly engraved with 5 small squares, and the maximum linear displacement that can be measured by the dial indicator is 1mm. The actual measurement is equal to the subdial reading + the large dial reading, which should be read to the next digit of the smallest scale, so if it is measured in millimeters, the measurement should have four digits after the decimal point.

Example of an application for the coefficient of expansion of metals.

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Indicates the degree to which the material expands or contracts. It is divided into the linear expansion coefficient of a certain temperature point and the linear expansion coefficient of a certain temperature range, the latter is called the flat ** expansion coefficient. The former is the elongation per unit length of the material per one degree of elevation; The flat expansion coefficient is the average elongation of a material per unit length at a certain temperature range for each degree of temperature increase.

Measurement method. 1. Ejector rod indirect method.

The ejector rod method is a classic method that uses the principle of mechanical measurement, that is, one end of the specimen is fixed on the end of the supporter, and the other end is in contact with the ejector rod, the specimen, the supporter and the ejector rod are heated at the same time, and the thermal expansion difference between the specimen and these components is transmitted by the ejector rod and measured. This type of instrument is divided into various types of instruments according to the specimen position (vertical or horizontal), the method of measuring the amount of expansion (direct measurement, electronic or optical method).

The most common application is inductive dilatometers. Its sensor is a differential transformer, also known as a differential transformer thermal dilatometer. Due to the long size of the ejector rod and supporter, it is difficult to achieve uniform temperature distribution in the heating conditions of the high-temperature furnace, and the amount of expansion between the ejector rod and the supporter is difficult to cancel each other, so the measured value of expansion needs to be corrected.

2. Telescope direct reading.

The telescope direct reading method is to use binoculars to directly observe the change value of the expansion of the sample at high temperature in the furnace, and calculate the linear expansion coefficient. The measurement temperature can be as high as 2000 °C, and the micrometer on the eyepiece directly measures the elongation of the specimen in front of the tomb. The specimen used is long, and the heating furnace should have sufficient constant temperature zone.

The disadvantage of this method is that it is generally not easy to record automatically. An automatic recording system for timed photography has now been developed.

3. Laser measurement.

Thermal expansion has been developed in recent years. It scans the specimen with a laser beam and continuously measures the change in the length of the specimen during heating. It is popular due to its high measurement accuracy, fully automatic control, recording and multi-function system composed of computers.

When choosing a thermal expansion measurement method, the rapid test range of the stool, the type and characteristics of the material to be measured, the measurement accuracy and sensitivity are mainly considered.

The coefficient of linear expansion varies depending on the substance, and its value is also related to the actual temperature and the reference temperature selected for determining length 1, but since the coefficient of linear expansion of the solid does not vary much, it is usually negligible, and a is regarded as a constant independent of temperature.

There are two calculation formulas.

1. Coefficient of Linear Thermal Expansion (CLTE):

l/（l*δt）

2. And volumetric thermal expansion coefficient:

1/v。(ξv/ξt)p

In most cases, this coefficient is positive. That is, the temperature rises and the volume expands. However, there are exceptions to this rule, when the water is between 0 and 4 degrees Celsius, there will be an anti-expansion.

However, some ceramic materials have almost no geometric properties change when the temperature increases, and their thermal expansion coefficient is close to 0.

The experimental procedure is as follows:

1. Install the hollow copper rod and aluminum rod of the sample on the test frame. Repeat the original length of the metal rod 2 3 times with a meter ruler at room temperature, record it in the table, and find the average asignage value of the original length of l.

2. Install the experimental device, connect the heating tube, and turn on the power switch so that the water level can be observed from the water level display on the instrument panel. The water tank has a volume of approximately 750ml.

3. Water addition steps: first open the water filling port at the top of the chassis and the plastic cover of the overflow nozzle at the back, add water from the water filling port to the system with a funnel, and the gas in the pipeline will run out from the overflow pipe mouth until the water level gauge of the system is only one red light above it, and the rest is turned into a green light, you can close the plastic cover of the overflow nozzle first.

4. Set the heating temperature of the temperature controller, and the general heating temperature setting value should be 1 50C higher than the experimental temperature value required for the metal book rental tube, and the specific temperature increase can be determined according to the temperature level.

5. The temperature sensor signal corresponding to the aluminum tube is output to the socket and the medium temperature sensor of the tester.

sockets are connected. Place the micrometer.

It is installed in the fixed position of the free telescopic end of the aluminum tube of the medium to be measured, so that the dial gauge is made.

The test end is in contact with the medium to be measured.

6. During normal measurement, the faucet of the non-measured specimen can be turned off, which can save energy and shorten the heating time. During the experiment, press the heating button under the posture (high speed or low speed can be, but the low speed gear can only be heated to about 500C at most due to the small power), and observe the change of water temperature and the temperature of the metal tube to be measured, until the temperature of the metal tube is equal to the required temperature value (350C).

7. Measure and record data.

8. Use the difference method.

Find the average elongation of the metal rod for every 5C increase in temperature.

Summary. Hello <>

The linear expansion coefficient experiment of measuring solids with a dial gauge takes the following measures to reduce the error:1First of all, choose a high-quality dial indicator to ensure its precision and accuracy.

2.Secondly, place the dial indicator in a stable position to avoid interference caused by external factors (such as vibration, wind, etc.). 3.

Thirdly, the temperature and humidity of the experimental environment should be controlled to make it as stable as possible and avoid errors caused by environmental changes. 4.Finally, the experiment was repeated several times to take the average value to further reduce the error.

What measures were taken to reduce the error in the linear expansion coefficient experiment of measuring solids with a dial gauge.

Hello <>

The linear expansion coefficient experiment of measuring solids with a dial gauge takes the following measures to reduce the error:1First of all, choose a high-quality dial indicator to ensure its precision and accuracy.

2.Secondly, place the dial indicator in a stable position to avoid interference caused by external factors (such as vibration, wind, etc.). 3.

Thirdly, the temperature and humidity of the experimental environment were controlled to make it as stable as possible and avoid errors caused by environmental changes. 4.Finally, the experiment was repeated several times to take the average value to further reduce the error.

Other measures can be taken to reduce the error during the experiment, such as using a more accurate instrument (such as a laser displacement meter), pretreating the sample (such as removing surface dirt or oxide layer, relieving stress, etc.), and avoiding errors caused by excessive operation during the experiment. At the same time, it is also necessary to pay attention to the recording and processing of experimental data to avoid errors caused by operation errors or calculation errors. Therefore, to reduce the error, it is necessary to start from many aspects to improve the accuracy of the experiment as much as possible.

Objectives: 1) To determine the wire expansion coefficient of A. chinensis in a certain temperature range;

2) Familiar with the principle and adjustment method of optical leverage.

Experimental instruments] digital display solid linear expansion coefficient tester, optical lever, ruler reading telescope, steel tape measure, triangular ruler or vernier caliper, metal rod to be measured.

Experimental Principle].The test principle "thermal expansion and contraction" is a characteristic of many objects and is caused by the intensification or weakening of the thermal movement of molecules inside the object. As the temperature of the solid increases, the average distance between molecules increases.

We call the phenomenon of a change in length due to thermal expansion the linear expansion of a solid. The magnitude of the change in length depends on the change in temperature, the type of material, and the original length of the material. Experiments have shown that

In a certain temperature range, the relative elongation of a solid with original length l is proportional to the change in temperature, i.e., where l0 is the length of temperature t 0, which is usually called the linear expansion coefficient, which is related to the properties of the matter constituting the object. Different substances have different linear expansion coefficients, that is, the same substance, its linear expansion coefficient is also related to temperature, but the influence of temperature is very small, and when the temperature change range is not bright, it can be regarded as constant.