Wednesday, 9 June 2010

Vibrograph

Vibrograph:

A Vibrograph is an instrument for observing and recording the ground mechanical vibrations.

How it is used:

This compact and robust instrument can be free standing on the bench, clamped to a bench, or supported horizontally or vertically from a retort stand. It is used for the lateral vibration of a cord at 50Hz or 60Hz frequency for experiments in standing waves and resonance. When used normally, the cord is tensioned by passing it over a pulley mounted at the edge of the bench and attaching the cord to a scale pan. Adding weights to the pan increases the tension in the cord. The active length of the cord is simply adjusted by moving the instrument on the bench relative to the position of the pulley clamped to the edge of the bench.

Apparatus:







AC supply, Pulley with stand, Pan, Light string about 2 meters long, Weight Box and a Meter Scale.

Construction:

For the purpose of measuring vibrations, a new instrument has been constructed and tested. The size of the instrument is so minute that it can be installed in small places. There is a bulb attached which passes the AC current and acts as an AC supply, then the current passes through an iron strip causes it to vibrate. The axis of rotation is kept constant. This type of axis of rotation is preferable for the instrument used in the measurement of vibration. Next to the strip a thread is attached in such a way that when the strip vibrates the thread also vibrates and at the other end of the thread a pan of some mass is tied to just over come the force of friction. As we calculate the frequency of AC supply through different observations, we also increase the weight in the pan gradually. In the last, we calculate the mean of the frequencies we observed before.

Working:

One end of a 2.5mm diameter steel rod is formed into a strong hook and the other end is firmly clamped by a thumb screw to a heavy metal base. The rod passes through the centre of a solenoid and between the poles of a permanent magnet. The rod is firmly clamped at one end by the thumb screw provided. When AC power is applied to the coil, the rod is magnetized and it vibrates laterally between the magnets when the vibrating length of the rod is set and locked to the correct resonant length. One end of the cord is tied in a loop to attach to the hook at the end of the vibrator rod and the cord is then passed over a vertical pulley clamped to the edge of the bench say 1 or 2metres away. A weight carrier or a scale pan is attached to the end of the cord to hang vertically. When the pan is loaded with weights, known tension is applied to the cord. As the rod vibrates, the taut cord can be seen to vibrate and standing waves can easily be examined and measured at different cord tensions and lengths. Active cord lengths exceeding 2 meters long can be used.

Diagram:







Caution:

For this instrument to operate and vibrate properly, the body of this instrument must be quite heavy. If the unit should fall on a user it will cause injury, therefore the shape of the stem has been designed so that if the clamping becomes loose, the unit cannot slide through the clamp and fall.

Modern techniques of measuring Vibrations:

The diffusion of vibration monitoring, which in the past was only conducted in high-risk situations, has become increasingly wide.
Vibration monitoring must become a standard in all production processes and all activities in which human, machine and facility safety and an ongoing increase in precision and automation levels are essential everyday issues.

As monitoring must take place using solutions able to recognize the specific nature of the process and activity to be controlled, SEQUOIA IT has developed products easy to program that exceed pre-existing technologies.

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