In a message dated 09/12/2008, sismos@.............. writes: Hello Dayana, Don't buy the black box that you see with an AS1. you can do much better and probably less expensive or close with Larry's boards. Hi Dayana, I believe that Jeff Batten _amateurseismo@.......... (mailto:amateurseismo@.......... will sell the electronics box and power supply separately. Seismometers like the AS1 and EQ1 try to use oil + plunge plate damping. The viscosity of oil changes by about x10 for every 20 C Deg / 36 F Deg change in temperature. If you set up the damping to be correct at your room temperature, you will only have an operating range of about +/-4 F Deg. This is LESS than the normal daily variation. If the temperature falls much below this range, the damping increases dramatically and the seismometer MAY stop recording altogether. It's sensitivity will certainly decrease and the calibration will NOT give the correct quake magnitude. I have designed a replacement magnetic damper which is NOT effected by temperature and is both easy to set up and CLEAN! No more oil creepage or spills! See _http://jclahr.com/science/psn/chapman/as1%20damping/index.html_ (http://jclahr.com/science/psn/chapman/as1%20damping/index.html) The AS1 uses a vertical swing arm with a natural period of about 1.5 seconds. So while the response is flat with velocity at periods shorter than this (like a geophone), the sensitivity will fall off as f^2 below 0.75 Hz when using a 'normal' seismic amplifier, like Larry's. The sensitivity to the 20 second period Rayleigh waves, will be down by a factor of about 180 - so you normally won't see any! A period extension circuit has been used in the AS1 'black box' to extend the sensitivity ~flat from 1.5 to about 4.5 seconds. This boosts the low frequency output. While it is OK for measuring microseisms, it is otherwise rather limiting. A further period extension can be applied with the digital compenation filter supplied with AmaSeis, but it only works well on moderately strong signals. I have extended the period to about 20 seconds by changing four capacitors and three resistors. It now seems to work satisfactorily and covers most of the normal seismic range. On the EQ1 that we examined, the compensation covered about the same compensation period range as an AS1, but the output seemed to be roughly proportional to f. This did NOT give a flat output. Since the power laws are different, I would not expect the digital frequency compensation built into AmaSeis to work adequately with an EQ1 trace. The EQ1 electronics uses miniature surface mount components, so I would NOT expect you to be able to modify EITHER the compensation range OR the power law. The relatively long springs expand and contract with temperature and may well need adjustment with the seasons. The AS1 is designed with the centre of gravity on the horizontal arm.In a message dated 09/12/2008, sismos@.............. writes:<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>Hello=20 Dayana,
Don't buy the black box that you see with an AS1.
you can do= =20 much better and probably less expensive or close with Larry's=20 boards.Hi Dayana,I believe that Jeff Batten amateurseismo@......... will sel= l the=20 electronics box and power supply separately.Seismometers like the AS1 and EQ1 try to use oi= l +=20 plunge plate damping. The viscosity of oil changes by about x10 for every 20= C=20 Deg / 36 F Deg change in temperature. If you set up the damping to be correc= t at=20 your room temperature, you will only have an operating range of about +/-4 F= =20 Deg. This is LESS than the normal daily variation. If the temperature falls=20= much=20 below this range, the damping increases dramatically and the seismometer MAY= =20 stop recording altogether. It's sensitivity will certainly decrease and the=20 calibration will NOT give the correct quake magnitude. I have designed a=20 replacement magnetic damper which is NOT effected by temperature and is=20 both easy to set up and CLEAN! No more oil creepage or spills!The AS1 uses a vertical swing arm with a natura= l=20 period of about 1.5 seconds. So while the response is flat with velocity at=20 periods shorter than this (like a geophone), the sensitivity will fall off a= s=20 f^2 below 0.75 Hz when using a 'normal' seismic amplifier, like Larry's. The= =20 sensitivity to the 20 second period Rayleigh waves, will be down by a factor= of=20 about 180 - so you normally won't see any!A period extension circuit has been used in the= AS1=20 'black box' to extend the sensitivity ~flat from 1.5 to about 4.5 secon= ds.=20 This boosts the low frequency output. While it is OK for measuring=20 microseisms, it is otherwise rather limiting. A further perio= d=20 extension can be applied with the digital compenation filter supplied w= ith=20 AmaSeis, but it only works well on moderately strong signals.I have extended the period to about 20 seconds=20 by changing four capacitors and three resistors. It now seems= to=20 work satisfactorily and covers most of the normal seismic range.On the EQ1 that we examined, the compensat= ion=20 covered about the same compensation period range as an AS1, but the output=20 seemed to be roughly proportional to f. This did NOT give a flat output. Sin= ce=20 the power laws are different, I would not expect the digital frequency=20 compensation built into AmaSeis to work adequately with an EQ1 trace. T= he=20 EQ1 electronics uses miniature surface mount components, so I would NOT=20 expect you to be able to modify EITHER the compensation range OR t= he=20 power law.The relatively long springs expand and contract= =20 with temperature and may well need adjustment with the seasons.The AS1 is designed with the centre of gravity=20= on=20 the horizontal arm.