Seismometer


Seismometer	Geophone

Background
Vibration Sensors
Hilger & Watts
Cal Tech
Geophone
Atomic Bomb Test Ban
Patents

Background

Seismometers & geophones are some of the sensor types that I find interesting. The applications are varied.

Earthquakes

Classically seismometers have been used to record the ground shaking as the result of earthquakes. By measuring the time from the "P" wave to the slower waves the radial distance between the sensor and epicenter can be calculated. The magnitude and duration of the slow waves gives an indication of the energy. This is the application that first got me interested.

Oil Exploration

Geophones are used to look for reflections caused by changes in density of sub surface layers after a surface explosion or a tamper initially shakes the ground. These are typically used in large arrays.

Intrusion Detection

Outdoor intrusion detectors use geophones as well as other methods to detect ground vibrations caused by moving men and machines. Knowing about the use of seismometers for recording earthquakes and then seeing this application reinforced my interest.

Machine Balancing & monitoring

Some industrial motors are connected to a system that can be balanced so sensing the out of balance helps make the initial adjustments.

In an industrial environment when a machine is breaking down or is about to, it starts to shake and detecting the vibration allows shutting the motor off before there's a catastrophic problem.

Detecting Nuclear Blasts

As part of the Non Nuclear Proliferation treaty a need arose to detect nuclear blasts and differentiate them from other types of blasts. Seismometers are able to do that by the wave form shape.

Vibration Sensors

There are a number of technologies used for vibration sensing. One of these is very similar if not identical to the geophone. The difference may be in the frequency range that's being monitored. Vibration sensors typically are concerned with audio frequencies and into the ultrasonic whereas geophones and seismometers are looking as infrasound frequencies.

Hilger & Watts

Label SG450, 157222, Made in England.
The Teledyne Geotech S13 Seismometer looks very similar.

Variable Oscillation Period Seismometer (see patent below) that can be used vertically or horizontally. Permanent magnet and coil of wire.


Hilger Watts Seismometer Open	Hilger Watts Seismometer Close Up	Bottom showing 2 of 3 possible windings

Mechanical

Diameter 6.625", height to top of handle under 15" (varies with leveling feet) 27.5 pounds.

Voltage Generator6 is a floating permenant magnet with a fixed coil (20) in the gap. Three bottom spokes 8 and two top spokes 10 locate the magnet so that it's free to move up and down (as shown in the patent drawing, but there's a way to use it on it's side).

Spring Lifting System

The arms (14) are firmly attached to the magnet by a central rod. Four triangular leaf springs (19) their base ends clamped to arms (14) and their pointed ends are linked (18) to the pointed ends of the top springs (19). There's a plate anchored to the frame (shown just above 26a) which holds brackets at the base of two of the top springs (19). One of these is shown in the upper left of the drawing. There are two Allan head screws that clamp the spring to the bracket (the upper left screw and another behind it not shown). There are two pivot screws whose ends sit on the plate (above 26a) shown as the single screw to the right of the bracket. The central screw goes through a clearance hole in the bracket and into a tapped hole in the plate. These two screws have horizontal holes in the head so they can be adjusted from the side.

Spring Lifting System - Not shown in patent drawing

Hilger Watts Seismometer Floating plate not shown in patent 3199072

The other two top springs (19) are held by an identical pair of brackets, but instead of being connected to the plate (above 26a) they are connected to a plate that's been cut out of the first plate. An an are bolted to the top of the plate (above 26a) and canterlevered out over the cut out section of plate. In it's outer end there's a tapped hole. The screw in that hole can be turned to cause the floating plate to move and this changes the tension of the spring system. The screw can be accessed by removing the large headed screw that holds the cover over the clamping screw (22). The highest dial setting that I can get to work in the vertical position is "18" and here the spring lifting system adjustment screw is backed out so that it's cantelevered are is almost touching the floating plate.

Setting Period

If the dial associated with the period adjustment (knob at top left) is set to full CCW it stops at about 23. But it's impossible using the spring lifting system screw to center the magnet (6) in it's range of travel. This might require using a pin to adjust the other two screws or some other adjustment, or maybe it can't be done. The resistor that caused critical damping when the dial was at 15 is much too weak when the dial is at 18 and the period is some number of seconds. It takes a number of cycles of ringing until the mass stops.

Electrical

The three coil termination pairs have letters scratched in the phenolic. Although there are positions for 6 output wires, on this unit only 4 are used. The patent mentiones that the damping needs to be adjusted for the selected period. This unit has two seperate coils, C-D (1k5 Ohms) and E-F (7k6 Ohms). There is a brown jumper between D and E thus presenting the full coil between C and F (White and Yellow). Connector pins B & F go to a pair of wires terminated swith a 6k7 Ohm resistor that I choose for best damping.

Coil Position	Wire Color	Connector
A	na	na
B	na	na
C	White	B
D	Blue	broken
E	Black	A
F	Yellow	F
Chassis	Red	broken

The connector is marked in the center of the insulating block 148-CP and has 6 male pins. Threads for mating shell are 0.864" O.D. mating insert OD liss than 0.691" O.D. with a single grove for keying.

Period

The dial calibrated from 0 to 25 which should change the period instead seems to move the mass up or down and when at 15 the rod in the height viewing dome is level with the center fudicial line. Moving this dial to either extream bottoms the mass.

The label on the outside "1NS" implies this was used in the horizontal position. But when placed horizontlly the mass locks up. So it's really not working correctly. There is probably something that needs to be done to get proper operation when vertical, which is the position I'd like to use.

Patents by Willmore:

3199072 Variable Oscillation Period Seismometer, Patrick L. Willmore, August 3, 1965, 367/185

3292145 Willmore Long Period Vertical Seismograph, Patrick L. Willmore

2909759 Sensitive Vertical Displacement Seismometer, George W. Cook, Oct 20 1959, 367/186 ; 327/518
2933715 Seismic Device, Beuermann (Firma Seismos, DE), Apr 19 1960, 367/184 ; 310/15; 310/27; 73/654 -

2939079 Method of Calibration an Electromagnetic Seismograph, Patrick L. Willmore

Cal Tech

3685011 Seismometer, Francis E. Lehner (Cal Tech), Aug 15 1972, 367/182 ; 73/654 - ciol in magnet type with calibration pulse input, maybe 5 second period (adjustable).

Calls:
3194060 Seismic Displacement Transducer, L.T. Greenwood (NASA), Jul 13 1965, 73/654 ; 367/179; 73/382R -
2074043 Seismograph, Louis Statbam (Std Oil), Mar 16, 1937, 367/182 ; 310/15; 73/654 - cylindrical package, down hole? permenant horshoe magnets
2873103 Seismological Instruments, R.F. Hautly, Feb 10 1959, 73/653 ; 73/514.14; 73/650 - torsional damped limited frequency response reflecting mirror

Calls:
1869828 Devices for Measuring and Recording Vibrations in Three Directions
2268526 galvaniometer
2487793 Object Controlling Electric Motor System, (Sperry Gyro) - used as part of aircraft auto pilot
2542018 Compass, Ferrill (Sperry Corp), Jr. et al, Feb 10 1951, 33/360 ; 33/362; 33/363Q; 73/504.14 - vibratory compass
2552722 Electromagnetic Accelerometer, John G. King, May 15 1951, 73/514.12 ; 324/127; 33/DIG.5; 336/135; 336/30; 336/67; 336/92; 336/94; 340/870.35; 73/514.31- magnet if bob of pendulum
2616681 Angular Velocity Responsive Apparatus, C.T. Morrow (Sperry Corp), Nov 4 1952, - ref 2513340

2842752 Geophones, W.M. Jones (British Petrolum), Jly 8 1958, 367/182 ; 267/160; 336/100; 336/136
2852769 Time Interval Multiplier, R.L. Plouffe (Navy), Sep 16 1958, 342/186 ; 327/134; 327/172; 327/174; 368/115

Geophone

This geophone is from the PSR-1 Seismic Intrusion Detector set.

12.7 oz.

Atomic Bomb Test Ban

By using a high dynamic range and wide bandwidth ( 10 seconds to 10 Hz) seismograph the difference between an earthquake and an explosion can be detected. The Vella Uniform project investigated how to do this. Keywords: Long Range Seismic Measurements

Patents

1784415 Electrical Recording Seismograph, H. Benioff (Carnegie), Dec 9 1930, 340/870.16 ; 310/15; 340/870.31; 340/870.44; 346/107.1; 346/65; 367/179; 367/182; 73/654

Called By:
2933715 Seismic Device,Beuermann, Apr 1960,

Calls:
1784415 <se above>
2269453 Device for Detecting Displacements, E.L. Gayhart, Jan 1942
2348225 Magnetic Seismometer, O.S. Petty, May 1944 - oil prospecting geophone
2576775 Seismometer System, F.D. Case (Diamond Inst), Nov 1951, - long period earthquake detection in small size
2683867 <See below>
2756406 Vibration Detector, G.S. Schurman (Calif. Research Inst), July 1956, - Frequency Response vs. Geophone mass - oil prospecting
2788512 Low Frequenc Seismometer, W.J. Reichert (Shell), April 9 1957,

2707776 Magnetron Type Seismometer, Cruzan (Phillips Petro), May 1955 -
2683867 Parachuted Radio Seismic Transducer, J.O. Vann (not assigned), July 13 1954, - for measuring polar ice
3225328 Transportable Seismograph, F Lecroart,

2111643 Seismometer, H. Salvatore (Western Geophysical Co), Mar 22 1938, - combine permenant magnets and coils - prospecting

Called by:
2418953 Transducing System, R.W. Raitt
2519916 Inertial Electromagnetic Throat Microphone, D.W. Martin (RCA),
2470244 ELECTRICAL REPRODUCING STYLUS - for machine shop duplicating
2562983 Frequency Adjustable Seismic Wave Detector, D.H. Clewell, Aug 7 1951, - oil prospecting
2643367 MAGNETOSTRICTION SEISMOMETER, (Phillips Petroleum Co)
2663088 Pendulum and Acceleration Compensation System, R.T. Cloud (N. Am Geo)
2540796 VIBRATION TRANSLATOR, A.N Stanton
2671202 VIBRATION PICKUP, M.O. Petroff (Stewart-Warner), Mar 2 1954 - wheel balancing
2595067 INERTIA TYPE VIBRATORY PICKUP, J.A. Flint (Jeffrey Mfg), Apr 1952
2659065 SEISMOMETER, R.L. Cordell (Stanolind Oil)
3066526 UNBALANCE DETECTION APPARATUS, H.R. Tear (Stewart-Warner),- wheel balancing
3480808 POWER GENERATOR, F. Rieth (Packard-Bell) - probably for TV remote
4740775 Automobile burglar alarm, R. Price,
4584569 Motion sensitive security system, M.J. Lopez,
5323133 Method and apparatus for making electrical connection with a movable member, - loudspeaker

These patents were found by looking for patents that are called by or call the Hilger & Watts patent.

------------------ Korean Conflict-----------
2533249 Seismic Detector, December 12, 1950, 310/25 ; 367/183; 73/496
2636160 Vertical Component Low Frequency Geophone, April 21, 1953, 318/680
----------------- Korean Conflict end -----------
2696592 Vib Pickup, December 7, 1954, 336/30 ; 335/285; 336/100; 336/136; 336/90; 73/654
2745085 Seismic Detector, May 8, 1956, 367/185 ; 310/14
2748370 Seismometer, May 29, 1956, 367/187 ; 174/77R; 267/160
2751573 App Chg Reas Freq, June 19, 1956, 367/183 ; 310/25

coil current changes reas freq and can be done on whole string.

2753544 Seismic Detector, July 3, 1956, 367/182 ; 267/159; 310/25; 73/654
2754435 Voltage Generating Vibratory Pickup Devices, T. Ongaro, International R&D, July 10, 1956, 310/27 ; 367/183; 73/661

Machine Balancing or Monitoring

2756406 Vibration Detector, G.A. Schurman, California Research, July 24, 1956, 367/184 ; 310/15

oil exploration

2764019 Vib Meas Dev, September 25, 1956, 73/654 ; 310/27; 73/661

rectify AC output and drive a meter, no batteries machine monitor

2788510 Seismic Prospecting Apparatus, April 9, 1957, 367/86 ; 174/70S; 367/176
2788511 Frequency Seismometer, E.H. Marshall, Texas Inst, April 9, 1957, 367/187 ; 267/161, - oil exploration
2788512 Frequency Seismometer, April 9, 1957, 367/14
2788513 Cable, E.T. Howes, United Geophysical Corp, April 9, 1957, 367/180 ; 174/102SC; 174/106R; 174/27; 174/71R; 310/338; 310/357; 367/154
2842752 Geophones, July 8, 1958, 367/182 ; 267/160; 336/100; 336/136
2923367 M App for Seismic sur, February 2, 1960, 367/34 ; 367/48; 367/58
2933715 Geophones, April 19, 1960, 367/184 ; 310/15; 310/27; 73/654
2939079 METHOD OF CALIBRATING AN ELECTROMAGNETIC, May 31, 1960, 324/537 ; 324/202; 367/13
---------------- Vietnam Era ---------------
2980042 Method for Planting Seismic Detectors, B. McCollum, April 18, 1961, 405/177 ; 111/199; 111/89; 343/719; 405/175; 405/183 - oil exploration
3020767 Linear Accelerometer, W.P. Kistler, KistlerInst Corp., February 13, 1962, 73/497 ; 267/160

feedback provices linear, sensitive operation

3057209 Seismic Vibration Pickup Means, K.F. Frank, Micro Balancing Inc., October 9, 1962, 73/654 ; 336/40

dynamic balancing machine

3067404 Vibration Detector, A.B. Hilderbrandt, Jersey Prod Res, December 4, 1962, 367/182 ; 310/15; 310/27; 73/652

oil exploration

3199072 Variable Oscillation Period Seismometer, August 3, 1965, 367/185

Hilger & Watts earthquake type

3202847 Tunable Vibration Pickup Device, L.H. Erickson, August 24, 1965, 310/14 ; 310/15; 367/184; 73/654

alarm or balancing equipment, reasonant type

3212057 Long Period Seismometer, F.E. Romberg, Texas Inst, October 12, 1965, 367/184

portable horizontal period much longer than equivalent pendulum, not as sensitive to tilt (tolerates 0.5 deg).
aimed at nuclear detection

3241375 Transducer, R.M. Canzoneri, Consolidated Electrodynamics Corp., August 24, 1965, 310/14 ; 310/15; 367/184; 73/654 - strain gauge type, instrumentation, tolerates hi G
3451040 Spring Suspension for Low Frequency Geophone, W.P. Johnson III, Mark Products, June 17, 1969, 367/183

oil exploration

3545286 Holder which is Displaceable Along one Axis, L.A. Stenstrom, Philips, December 8, 1970, 248/604 ; 267/154; 267/160; 73/514.24; 73/654
3577184 Low Distortion Seismometer, W.O. McNeel, Geo Space Corp., May 4, 1971, 525/342 ; 525/332.9; 525/333.1; 525/333.2; 525/359.1; 525/359.3; 525/359.5; 525/359.6; 525/361; 526/240

oil exploration

3582874 Electrodynamic Seismic Receiver, N.E. Fedoseenko, June 1, 1971, 206/6.1 ; 206/366

oil exploration

3582875 Geophone Device, S.H. Van Wambeck, June 1, 1971, 206/433 ; 229/120.23; 229/120.27

oil exploration

3609674 Seismometer, S. Hansen, Hughes Aircraft Co., September 28, 1971, 65/135.7 ; 373/27; 65/136.4; 65/324; 65/327; 65/347; 65/356 - bubble movement is sensed and a PID feedback loop provides wide bandwidth

---------------- Vietnam Era ends---------------

4043175 Automatic method and apparatus for digitally indicating response characteristics of geophones of a geophysical data acquisition system 4259563 Method for dynamically tuning a seismic transducer
4323994 Geophone Spring, J.M. Coogler, Geosource, April 6, 1982, 367/183 ; 267/158; 267/161; 367/187
4458344 Tapered Geophone SpringJ.M. Coogler, Geosource, July 3, 1984, 367/183 ; 267/161; 367/187
4623991 Delta Shaped Geophone Spring, F.A. Vitringa, Geosource, November 18, 1986, 367/183 ; 267/161; 367/187
5113375 Method and apparatus for testing geophones
5134593 Geophone Spring, R.M. Logan, Western Atlas Intl Inc., July 28, 1992, 367/187 ; 267/141.3; 367/183
6658362 Method and apparatus for testing components
6816434 Seismic detection