Abstract:
A sounding vibrometer which is characterized in that it comprises a sensor comprising a geophone with its test-lead point mounted by way of a plurality of cable-type damping devices on small columns rigidly attached to a plate affixed to a tubular section of a segmented rod.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a sounding vibrometer and, more particularly, to a portable, self-contained device for detecting, measuring and indicating the particulate speed in a rock mass. 
     SUMMARY OF THE INVENTION 
     The device according to the invention comprises two separate parts: firstly the sensor per se with its handling rod and secondly the electrical box; these two parts being interconnected by way of a flexible electric wire. The invention will be described with reference to the following figures which are provided by way of non-limitative examples only. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic view of the sensor. 
     FIG. 2 shows the assembly of the sensor on its rod. 
     FIG. 3 is a block diagram of the electrical part. 
     FIG. 4 is a graph of the response of the low-pass filter shown in FIG. 3. 
     FIG. 5 is a perspective view of the electrical box. 
     FIG. 6 shows the side panel of the box shown in FIG. 5. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to FIG. 1: the sensor 1 per se comprises a geophone 2 with its test-lead point mounted by way of two cable type damping devices 4 on three or four small columns 5 rigidly attached to a plate 6 by means of a screw 7. With reference to FIG. 2: the rod 11 which is made of zicral or fiber glass consists of four tubular sections 12 adapted to be snapped together by way of three connections 13 (bayonet type or automatic connections) so as to obtain a rod which is 1.50 m, 3m, 4.5 m, or 6m in length as desired. The unit only has to bear a force in the order of 2kg by weight which is necessary to rest the test-lead point 3 on the rock mass R. The electric wires 14 of the geophone pass through the rod 11 which they leave at its lower part. These wires are preferably incorporated in tubes 12. The connections 13 safeguard the electrical connections and the lead out wire consists of extensible wire (the type of wire used for telephone sets). 
     With reference to FIG. 3, which is the block diagram of the electrical part: the input signal 21 which may be damped by means of a switch 22 in series with a resistance 23, for example, of a 200 ohm resistor connected to ground, is applied to a low-pass filter 24 with an input impedance of at least 5 kΩ. The filter is designed to eliminate the high frequencies produced at the contact point of the test-lead point 3 and the rock mass R. This low-pass filter possesses, for example, an attenuation from 450 Hz of 12 decibels per octave - as shown in the graph of FIG. 4. The low-pass filter 24 is followed by an amplifier 25 having an adjustable gain. This is followed by a rectifier 26 and then a converter 27 which effects the analog-digital conversion, for example, at a conversion rate of 10 4  pulses per sec. per volt. The converter 27 drives an integrator-indicator 28 which indicates a number N proportional to the integral: ##EQU1## WHERE V (T) IS THE PARTICULATE SPEED OF THE ROCK MASS AS DETECTED BY THE GEOPHONE AND T O  IS THE TOTAL DURATION OF THE VIBRATION. With reference to FIGS. 5 and 6: the side panel 31 of the box 32 comprises -- apart from the input 21 and the switch 22-- an indicator 33 indicating the state of the cells, a data indicator 34, a zero resetting knob 35 and a stop-start switch 36. The data indicator 34 is designed for 3 characteris of the seven segment type each character being at least 6 mm in height and clearly visible one meter away. The return-to-zero knob 35 triggers a time delay of, for example, 5 seconds, during which the letters are illuminated and it is possible to read the same. The supply to the data indicator is then interrupted. In the case of an overrun, the data indicator stops at 999 which indicates this overrun. The box 32, which is provided with a carrying strap 37 and a cover 38, holds in its lower part 39 cells (not represented) or batteries (not represented) adapted to be recharged by means of a mains charger. 
     Purely by way of indication, with a battery permitting automatic operation for two or three hours, the box can measure 8 × 12 × 20 cm and weigh approximately 1500 grams.