I have a data sheet from Mark Products for the L10B.  Here
are the published specifications:

Frequency tolerance  		+/- 0.5 Hz
Standard coil resistance 	138 or 215 or 374 ohms +/- 5%
Maximum distortion at resonance	0.2%
Transconduction Constant	0.041*sqrt(Rc)  V/in/sec
Open Circuit damping		1.908/f
Coil current damping		(12.15*Rc)/f(Rc+Rs)  Rs = R shunt, Rc
= R coil
Suspended mass			17.00 grams
Power sensitivity		1.67  mW/in/sec
Case-to-coil motion		0.080 in p-p
Basic unit diameter		1.25 in
Basic unit height		1.4  in
Basic unit weight		5.0 oz

The basic unit is the metal cylinder inside the case.  60%
damping looks like a good number, use a high-impedance
amplifier.

macsmith wrote:
> 
> Hi,
> 
> thanks for the replies.  I've just done a search of the mail archive (which I should have done
> fiirst!) and found:
> 
> > The 4.5 Hz is Mark Products L10B single vertical geophone in aluminum case
> > with 2 3/4 inch spike,3 foot lead and Amphib IV connector.  They have a
> > shunt resistor soldered across them for approximately 60% damping.
> 
> > The coil resistance for the 4.5 hz sensor is around 220 ohms.
> 
> So it looks like I just connect it straight to my amp.
> 
> cheers
> 
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-- 
Doug Crice          web site http://www.georadar.com
GeoRadar Inc.             e-mail dcrice@............
19623 Via Escuela Drive           phone 408-867-3792
Saratoga, CA 95070 USA              fax 408-867-4900

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