When strain measurement of structures and materials of different types of equipment used for static measurements.
ISD 3 - meter with manual trim. Transistor strain gauge with manual trim ISD -3 is designed for the measurement of static and slowly varying strains in one or many locations , has a built-in switch for 20 points and allows a multipoint connection switch. The device is made by the block diagram of the amplifier at the carrier frequency. To power the device used in the bridge rectangular pulses with a repetition rate of 275 Hz from the generator placed in the device.
Figure 1. Controls and adjustments meter ISD -3 with manual trim.
Fig. 1 shows the front panel of the instrument. In the lower right corner of the range is available with a slide wire dvuhstrelochnym pointer 2, Above the scale indicator is set zero 5, which is also the instrument of control voltage power supply, plug- tumbler 6. 5 is a toggle switch to turn on the device, and switch 6 - to monitor the bridge circuit without measuring path. 4 toggle switch on the device group or pair of strain gauges inclusion. The scale adjust pin. When you connect up to 20 half-bridges to plug connectors 7 channel switching is performed switch 4. Single half-bridges connected to terminals 5, these jumpers after 9 attach an external switch to any number of channels.
Strain gauge with automatic balancing of AID- 1M is designed for the measurement of static and slowly varying strains in one or many locations. In the latter case, the device is used with the switch. The device is made by the block diagram of a compensator with a reversible motor. Meals tensor meter ica bridge is powered by the 50 Hz. Input of the device is designed for half-bridge circuit incorporating strain gages.
Fig.2. Controls and gauges with automatic tuning and balancing à - AID- 1M, b - AID- 2M, â - AID- 4, g - view of the rear panel.
Fig . 2, and shows the front panel of the instrument. In the center is a scale of 1 to reohorda dvuhstrelochnym pointer 2, the light indicator balance in phase 5, the controller 4 of balancing the bridge by the reactive component, the main power switch 5, 6 terminals for connection of strain gauges or switch and ground terminal 7. On the back of the unit ( see Fig. 2d) placed pin 8 cord of your appliance, handle 9 gain control device , which is used to obtain optimal time reading to stabilize ( after one or two oscillations relative to the position of balance ), the switch 10 - voltage network power switch 11 and voltage of the bridge, as well as handle the zoom 12.
SENSORS OF PHYSICAL PARAMETERS
• During the test designs for measuring small deformations of concrete (elongation or shortening) used strain gauges that allow you to record these deformations with high magnification.
Depending on the design features of the strain gauges can be mechanical, Electromechanical, string, wire strain gauges are resistance etc.
Mechanical strain gauges. Among mechanical strain gauges are the most widely gugenberger of the strain gauge consisting of a body, supporting part which is executed in the form of a cone and prism, the latter is attached to the lever. Between the stand device and the lever with a hinge attached needle. The deformation of the support surface between a cone and a prism at the distance x there will be a rotation of the prism at some angle. For the same angle of turn and connected with her arm, which will cause deflection in one direction or another. When installing the strain gauges need to be sure that they are not located in places, which when tested, there may be local stress concentration.
Widespread in probation practice are strain gauges Aistova TA-2 and TA-3, with enhanced stability and reliability when testing. These strain gauges due to the presence of a disk allows to measure deformations in a wide range without relocating the device. The strain gauge consists of three parts A, B and C, of which the upper part And electroisolation from the other two parts. The support portion of the device has two prism — movable member in the groove of the plug, and stationary. In the upper part And has a split sleeve, through which passes the micrometer screw tightly impaled on his disk. The disk has a scale, calibrated in millimeters. Parts A and B are connected to a generator of high frequency signals. When measuring deformation of the tip of the micrometer screw by rotating the disk counterclockwise to bring the contact area of the pen, with the result that the electric circuit is closed and the beeping sound does count. Then the disk rotates in the opposite direction the edge microvita is removed from the pen and the action signal stops.