Development of Biomedical Dynamometer for Measurement of Grip Strength in Mice Modeled with Cerebral Palsy

This research aimed to develop a biomedical dynamometer capable of measuring the grip strength of the forepaws of laboratory mices to verify the posterior phase, the effect of modeled cerebral palsy in the animal. The equipment was developed using a stainless steel blade, two double strain gages, a signal conditioning circuit that was connected to a software for acquisition, processing and plotting of graphs and tables in Excel. The metal blade has a length of 18.5 cm, a width of 1.5 cm and a thickness of 2 mm and a double strain gage model pa-09-125ha-350-l8 from Excel Sensors (Brazil), was glued to each face. The two double strain gages were connected in a Wheatstone bridge, which produces an analog response due to mechanical deformation of the blade, with force applied by the mice. This response was submitted to a signal conditioning circuit developed with Arduino that modulated the input wave, generated 10000 times amplification and performed filtering 4th order using Butterworth filter. Finally, a software developed in Labview 2019 of National Instruments (USA) was used for acquisition, processing and plotting of graphs and tables in Excel of the measurements performed. In the next step, the dynamometer was calibrated for sequential loading of masses of 0, 15.48 g, 31.53 g, 46.88 g to 62.47 g and also for sequential unloading of the same masses. For this, the masses were hung on a nylon string that was attached to the free end of the metal sheet. The final test was to measure the response time of the dynamometer with a stopwatch, when hanging a mass of 62.47 g on the nylon thread that was cut abruptly with scissors. Some of the main results of the calibration were as follows: 15.48 g generated 3.70 V, 31.53 g generated 7.48 V and 62.47 g gene rated 14.80 V and the response time was 0.3 s. These answers show that the dynamometer can be used to measure the grip strength of mice and can be modified for use in humans.

JUSTIFICATION OF TENSORISTOR CALIBRATION IN A COMPLEX WITH MEASURING EQUIPMENT

The article describes the process of calibrating strain gauge and measuring equipment. Modern machines have a complex design of the shapes of parts and assemblies. The loads acting on them often do not allow the determination of the stress state by modeling or calculation when creating these structurally complex machines. Therefore, conducting experimental studies using the strain gauge method is an extremely important task in real time. But for such a study, it is necessary to calibrate the strain gauges. Calibration must be performed to determine the functional relationship between the load applied to the part to be tested and the equipment output. Depending on the size, as well as the configuration and other features of the investigated part, several methods of calibration of strain gages are used: direct and indirect. To obtain reliable measurement results, the calibration conditions should differ as little as possible from the conditions of experimental studies of the tested parts. Calibration must be performed to determine the functional relationship between the load applied to the part to be tested and the equipment output. Depending on the size, as well as the configuration and other features of the investigated part, several methods of calibration of strain gages are used: direct and indirect. To obtain reliable measurement results, the calibration conditions should differ as little as possible from the conditions of experimental studies of the tested parts. Calibration consists in finding a functional relationship between the load acting on the tested part and the output signal of the equipment. To do this, creating previously known loads on the part on which the strain gauges are glued, and comparing the value of these loads with the intensity of the output signal, their ratio is determined analytically or graphically. Electrotensometry uses bridge and half-bridge measurement circuits. The half-bridge circuit is widely used, especially in static processes, where one strain gauge is active, and the other is located in the area of the load and is used for temperature compensation.

AUTOMATED DEVICE FOR MONITORING THE STATOR CORE OF POWERFUL TURBOGENERATOR

A device for automated control by the stator core of a powerful turbine generator (TG) during assembly and pressing at the manufacturing plant is proposed. Using the device, places in the core with a weakened solidity are determined. For this, at N points evenly spaced along the cross section of the stator core, the specific pressing pressure of special plastic elements, which are installed in the control cells of the additional pressure ring of the press, on which the core is assembled, is measured. During pressing, the elements are deformed, and their deformation depends on the degree of core defect (decrease in solidity) in the zone of which they are located. The sample will be deformed less, located in the zone of the largest defect, and most of all - in the zone where the defect is minimal. The pressure is measured using a flat metal membrane with a rigid center on which strain gauges are located at selected points. It is shown that the relative deformations in a flat membrane, which are measured by strain gages, depend on the value of the specific pressing pressure. Analytical relationships between the relative radial and tangential deformations and the specific pressing pressure have been determined. References 20, figures 5.

Strain gages based on gallium arsenide whiskers

Strain-resistant properties of GaAs whiskers and ribbons of p- and n-type conductivity with various length (0.3–7 mm) and diameter (10–40 μm) have been investigated in a wide range of temperatures. Strain gages based on heavily doped p-type conductivity GaAs whiskers have linear deformation characteristics and a weak temperature dependence of strain sensitivity in the temperature range from –20 to +3500 °C. The temperature coefficient of resistance (TСR) of not fixed strain gages is about +(0.12–0.16)% × grad–1. The temperature coefficient of strain sensitivity is –0.03 % × deg–1 in the temperature range –120+800 °C. Strain gages based on n-type GaAs ribbons are characterized by high flexibility and high strain sensitivity. They are capable up to +4000 °C and can be used to measure deformations on curved surfaces at high temperatures. TСR of not fixed strain gages is –0.01 +0.03 % × grad–1. The temperature coefficient of strain sensitivity is –0.16% × deg–1 in the temperature range –120 ... +4000 °С.