ML20148B260

Velocity Recorder Model C Operating Manual

ML20148B260
Person / Time
Site:	Limerick
Issue date:	01/15/1980
From:	VIBRATION MEASUREMENT ENGINEERS, INC.
To:
Shared Package
ML20148B258	List: ML20148B256 ML20148B260 ML20148B265 ML20148B270
References
PROC-800115, NUDOCS 8001210279
Download: ML20148B260 (8)

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Introduction............................................ 1 S pe ci f i c a ti o n s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Principle............................................... 2 Operation............................................... 2 Field Use............................................... 4 Maintenance and Care.................................... 5 F11m.................................................... 6 - i Serv 1ce................................................. 6 I

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INTPODUCTION The Veolcity Re eorder is a self-contained, portable seismograph MBri weighing 37 pounds, making it possible to hand-carry into almost any location for the purpose of making a permanent seismic recor-ding.

The velocity Recorder will record seismic waves created by various sources, such as rock blasting, pile driving, heavy machinery operation and many other operations which produce shock impulses in the earth. The seismic waves created are generally of a very short duration, usually lasting less than one second.

The Velocity Recorder is an electro-mechanical device containing a velocity trrisducer, solid state amplifiers, galvenometers and optics to display the velocity waveform on a permanent recording film.

The features of this instrument allow it to be used in confined areas, to be rapidly set up for operation, and to make records available for interpretation within minutes after measurement.

SPECIFICATTONS Hodifications to the instrument may occur in the future, as devel-opment work is constantly in progress. The general specificatiens j for the Velocity Recorder Model C are as follows:

pORTAPtE VELOCI"'Y SEISMOCRAPH I

Frequency response 10 to 250 Hz Sensitivity -

1.0 inch /1.0 in./sec.

(peak to peak)

Timing Oscillator output 100 Hz Ga.1vonometer Natural Frequency 4 Hz Recording paper 70mm Astroprint, L'ao-graph, Linowritt Kodak 2022, Kodak 1855.

P ower (Batteries rechargeable) 24 Volts DC 12 Volts DC Size Recorder 9"x9-3/4"x19-3/8" Transducer 5-3/4"x5-3/4"x4-3/4" Carera Magazine 6"x3\"x2 "

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Wei ght Transducer 6 Lts.

Camera Magazine 2 Lts.

Total Weight (Recorder & Trans-ducer) 37 Lbs.

PRINCIPLE The Velocity Recorder is a two-piece assembly consisting of a transducer assembly and a recorder assembly.

The transducer assembly converts the relative mechanical motion l tetween the magnet and coil assembly to an electrical output, this being in proportion to the velocity of the magnet. Three such elements are included in the transducer assembly to provide an electrical output in three axes, each at 90 degrees to each other, and further identified as the longitudinal, transverse and verti-Cal Exes.

Contained in the recorder assembly are high gain solid state am-plifiers for each axis, to amplify the transducer out put voltage.

The output of the amplifiers is used to deflect the gulvonometers for optical registration of the waveform at the film plane in the camera magazine.

A time reference, as a separate channel, is placed on the upper edge of the film record by a 100 cycle oscillator. This pulse may be used for obtaining the frequency of the seismic wave from the record.

Examination of a typical record shows the time base channel at the top of the record, followed by the longitudinal channel, the vertical channel and then the transverse channel.

The reccrder is powered by a nickel cadmium battery supply. A 12 VDC is used to drive the galvonometer lamp and the motor cir-cuit. A 24 VDC supply is used to drive the amplifier and escil-lator circuit. The batteries are rechargeable and a charging cord has been provided f or this purpose. .

OPERATION The operating instructions which are described in the following paragraphs also appear on the inside surface of the recorder case cover. The voltage level of the batteries should always te mai_n-tained eteve 22 volts refore usinc. If the voltmeter inEIcates a Tower voltage wnen the operate switch is turned on, the batteries must then be recharged.

TRANSDUCER CONMECTIONS TO RECCRDER

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1. Open the center door of the recorder and rotate the l large knot to left until threads disengage. Lift the j transducer unit cut of the storage compartment.

2. Connect transducer unit to recorder with cable having male electrical connectors at each end. The cable ends are interchangeable. Compartment must be empty and the door closed before using instrument.

LEVEiING TRANSDUCER

1. Place the transducer unit en any firm, flat surface.

2. Point arrow toward source of vibration.

3. Adjust the levelAng knots Lt least three turns, until the transducer is supported by the three leveling legs only.

4. Adjust leveling knots until the spirit level buttle is centered.

POWER CHECX

1. Before inserting recording camera, turn the " Operate" switch "On" for five seconds, and observe volt meter.

If r. ster reading is below 22 volts during operation, the power supply must be charged before using the re-corde~.

OPERATE RECORDER

1. Insert camera into camera compartment and make a five second pre-run to insure proper fit of camera with drive gear.

2. Turn " Operate" switch on fif teen seconds before test event. The camera contains 60 seconds of recording film.

AFTER THE TEST After each test and before transporting the instrument, observe the following:

1. Place the " Operate" switch in "of f" position.

2. Remove the connecting cable.

3. Fully retract the transducer leveling legs.

4. Observing the index notch in the top panel for the socket, replace the transducer in storage.

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5. Lock the Transducer in position, using the retaining knob, and close the transducer compartment door.

6 Coil and replace the cable and Cord inside the cover.

Do not store in the transducer well.

7 Remove the Exposed Camera, noting date, time of test, and camera number on the accompanying field card for identification later.

8 Replace the Recorder cover.

WARNING: To insure adequate power for test measurement, the Recorder must te kqp_t en Charce when not in use. Con-nect the FEciiUer toiny sEEKU3rcT ITOTE@cie elee-trical outlet using charging cord. Light will indicate when batteries are being charged. Do not store in transducer compartment.

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The small size of the transducer permits it to be sct up in a variety of situations. When placed on concrete, blacktop or a similar surface, the resting surface for the transducer must be free of pettles, gravel or other foreign materials. The arrow on the transducer should be pointed towards the source of the vitra-tion. This aligns the transducer elements to the sourec.

If the protection of privately owned structures is of interest, then the Velocity Recorder should te set up at some intermediate location, either between the vibration source and the nearest structure, or at the nearest structure. When placed in the in-terior of a building, the transducer should te placed on the ficer 1 near the corner of the intersection of exterior walls. The analy-sis of subsequent records will make possible the evaluation of the propogated wave at the instrument location.

In a similar manner, a chart or curve may be developed for con-ditions at fixed operations such as a quarry, mine, or construc-tion site, by measuring a series of blasts to eventually forecast the seismic effect for explosive charges at varying distances.

A conservative representation of a blasting table is shown telow, which will serve as a guide in many situations. However, due to '

the dif ferences in geological conditions from one location to another, and also due to the differences in blasting techniques, guaranteed results cannot be assured using the table.

When blast events are to be measured, coordination with the blas-ter and the velocity instrument operator will te requiredt usually stop watches or citizen hand transmitters and receivers are used for this purpose. This coordination is necessary since each camera s

magazine has 25 feet of film, which permits a recording time of 60 seconds.

It is good practice to start the Velocity Recorder 15 to 20 seconds before the scheduled blast. This will place the wave-form into the first third of the film, away from the start of the film roll, where fogging of the film might occur if the maga-zine has tean exposed to tright sunlight.

The operatitg tre* ructions on the inside surface of the Velocity Recorder a: e simple to understand and should be followed prior to each measutement.

BLAST TADLE hinimum Distance Maximum Explosive Lts.

( ree t) Per Delav Period 50 feet 1.5 to 3 lbs.

100 reet 5 to 12 lbs.

200 feet 25 to 50 its.

400 feet 100 to 200 lbs.

600 feet 225 to 450 lbs.

1000 feet 625 to 1250 lbs.

2000 reet 2500 to 5000 its.

MAI NT f! ANCE AND CAP E ,

The Velocity Recorder is a delicate instrument, much like an oscillosecpe, oscillograph or other electronic device. It must te handled with reasonable care in order that the electronic cir-cuits are not jarred out of adjustment to cause inaccurate read-ings. The instrument should be stered inside, preferably in a heated building, at least two to three hours tefere it is planned to te used. If it has not been used for a period of one week, it should then te placed on charge fer at least twelve hours before using. The instrument should not te carried on the back decks of pickup trucks or other siedlar vehicles, unless it is contained in a suitable carton.

The Velocity Recorder will function on fully charged tatteries over a wide temperature range. It is recommended that the tat-teries te charged when the voltreter indicates 22 volts or less, as inaccuracy of results will occur at lower voltages.

1 The type of batteries used in this instrument permit a great number of recharge cycles. Under normal usage, the tatteries should last for two or three years.

I Annual maintenance is recommended for the Velocity Recorder to check the calibration of the instrument, to clean the mirrors and lenses of the optical rystem and to generally cleen up the inter-ior, since the operating environment of mines and quarries is i very dusty.

i FILM i

! There are two categories of film that may be used in the magazine

] for the velocity Recorder. The instrument was developed to use a

direct print film which may te developed by exposure to incandes-cent or fluorescent light. The waveform appears in generally two to three minutes af ter such exposure. Some of these direct print d

films may lose their image when exposed to tright sunlight and care should be exercised in this regard. There is a direct print film j only recently introduced on the market, which can te exposed under a

direct sunlight. This should not te attempted unless this type of film is known to be in the camera magazine. Direct print films should te permanently fixed by rinsing in photograph developer and then fixer, to insure that the image does not fade in time.

1 Develop-out films, such as Seismolog film, are the second type that may be used if direct print film is not available. However, the normal photographic film processing fermulae and techniques i for the particular film must te followed. Either type of film j should be leaded into the magazine in a dark room. Twenty-five I foot rolls are commonly used to provide 60 seconds of recording capacity.

SERVICE

• j The Velocity Recorder is guaranteed f ree of def ects. Damege to 3 the instrument as a result of improper handling will be chargentle to the instrument user. The Velocity Recorder may be recalled at a

a future date to incorporate modifications er improvements. If

) parts or instrument servicing is required, please contact the i Operations Manager of Vitration Measurement Engineers at the Evan-j ston effice. l j

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