Rotometer
The syphilis rotary oscillator is mainly used in the syphilis serum test. It is suitable for the slow eccentricity and rotary rotator of the USR slide method and the RPR paper method. It is also suitable for other biochemical tests such as blood coagulation. The instrument has slow rotation speed, low noise, stable operation and simple operation. It is an indispensable instrument for syphilis serum tests in major hospitals, teaching and research units, STD centers, health and epidemic prevention stations, and blood stations.
Specific operation of a rotator
According to the law of the fixed axis rotation of the rigid body, as long as the external moment received by the rigid body and the angular acceleration of the rigid body under the action of the moment are measured, the moment of inertia of the rigid body can be calculated, which is the constant moment rotation method for measuring the moment of inertia. Basic principles and design ideas. First, the measurement principle of the moment of inertia J The weight plate and its weight are the power of the system rotation. Analyze the force of the rotating system as shown in Figure 2: When a certain weight is placed on the weight hook, if the hand is released, the weight will drive the tower wheel to accelerate the rotation through the string under the action of gravity. When the weight rope is removed from the tower wheel, the system will only rotate under the action of the frictional moment.
Torque system force diagram In this experiment, the test piece is placed on the test bench, and the fixed axis rotation is performed along with the test bench. When the empty test bench (without the test piece) is rotated, its moment of inertia is, and the moment of inertia after the measured rigid body is obtained. According to the superposition principle of the moment of inertia, the moment of inertia of the tested piece is or experimental. The moment of inertia of the system bracket (empty test bench) is measured, and then the object to be tested is placed on the bracket, and the moment of inertia is measured. The moment of inertia of the object to be tested can be calculated by the above formula. When the test piece and external force are not added ( , ), that is, when the external torque is zero, if the system starts to rotate at a certain initial angular velocity, the system will make a uniform deceleration rotation under the action of the friction torque, and set the angular acceleration to be By the law of rotation of rigid bodies
(1) Where (2) after adding external force (that is, there is external torque), set the angular acceleration of the system to be: (3) and (4) where - the mass of the weight, - the acceleration of gravity, the tension of the rope Equations (1), (2), (3), (4) are obtained: (5) After measurement and addition of external torque, it can be obtained by (5), and will be substituted for (1) The friction torque is produced. Similarly, after adding the test piece, there is (6) or more, which is the angular acceleration generated by the friction torque, and its value is negative, so the denominators in (5) and (6) are actually added. The experimental sequence of the test may be , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,
Second, the measurement principle of angular acceleration is measured as follows:
The direct measurement of time and angular displacement in the experiment can be indirectly derived from the following calculations. Let the initial angular velocity of the rotating system be 0, and the angular position at t=0 is 0, then the angular displacement at time t is (7) the number of milliseconds is counted from t=0, and the number of times at this time is k=0, ; =1, ;t time, the number of times is k, angular displacement. If the measured time is the corresponding time, then the number of times is: (8) (9) simultaneous (9), (10): (10) ie: ( ) (11) can be calculated by two sets of values Values ​​can also be selected by multiple groups to calculate several values ​​for averaging; or multiple direct measurements. This experiment uses the ZKY-J1 universal computer timer to time and record the angular displacement. Third, verify the parallel axis theorem parallel axis theorem: the rigid body of mass m, the moment of inertia of a certain axis of rotation over its centroid c, then the moment of inertia of the rigid body to another axis parallel to the axis and its distance d Therefore, if the moment of inertia of the system bracket is added to both ends of the above equation, there are: order, and both are fixed values, then J has a linear relationship. If the relationship is measured in the experiment, the parallel axis is verified. theorem.
3. The "theoretical" formula of J is that the mass of the disk (or cylinder) to be measured is the radius, and the theoretical value of the moment of inertia of the disk and the cylinder around the geometric central axis is the mass of the ring to be tested, and the inner and outer radii are respectively For, , the theoretical value of the moment of inertia of the circle around the geometric center axis [Introduction to the experimental instrument] The moment of inertia: consists of a cross-type stage, a winding tower wheel, a light-shielding rod and a small pulley, as shown in Figure 3.
When the stage rotates, it is fixed on the edge of the stage and rotates along with the light-shielding thin rod. Each rotation of the half-turn ( ) blocks the photoelectric gate fixed at the opposite ends of the circumference diameter of the base, that is, a photoelectric pulse is sent to the photoelectric timing counter. The counter will count the time and the number of occlusions. The counter counts, counts, and continuously records from the first stop (the first photo pulse occurs), storing multiple pulse times. There are five different radius reels on the tower wheel
The radius of the middle one is 2.5cm, and the radius between each adjacent two tower wheels is 0.5cm. A certain number of weights can be placed on the weight hook, and the heavy moment is used as the external torque. The structure is as shown in Fig. 3: The structure diagram of the moment of inertia instrument ◠The method of using the instrument: 1. Connect the photoelectric door to the general computer timer with a cable. Turn on one way (the other way is standby); 2. Turn on the power and the instrument enters the self-test state. a) 8-digit digital display tube lights up at the same time, otherwise the unit has an error; b) The digital display shows that the system is composed of one photoelectric pulse for each group of pulses, there are 80 groups of pulses (all system default values) 3. System adjustment Method: a) If there is no need to modify the system or have been modified, press “Test/+†to enter the work waiting state; b) The first two digits of the timing display are the number of photoelectric pulses per group, and the last two digits are the number of recording groups. For flashing digital display bits, type this number directly to modify this bit;
If you need to modify the next digit, you must press the " /-" button, the next digit display bit flashes, and then type the number to modify it, while retaining the modified value for other bits. Use the “/-†button to cycle the modified four-digit digital display. The number of recording groups is up to 80. 4. Press the “test/+†button to enter the work waiting state: the digital display shows 5, enter the timing working state. : Start counting and counting after the first photoelectric pulse entered. 6. Timing end: When the number of measurement groups exceeds the set number of record groups, the digital tube displays: The timing is over. 7. Data query: Each time the “test/+†button is pressed, the number of record groups is incremented by one, and each time the “/-†button is pressed, the number is decremented by one. 8, the computer timer reset, in order to carry out the next test
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