In a message dated 2007/02/27, jonfr@......... writes:

> I got new hardware from larry today and I was setting it up. I have
> problems setting up the gain for Channel 1 (Z). I don't get it up as hig
> as I want. This can be seen on my online plot now, when a earthquake
> appears on E-W and N-S, it doesn't appear on Z.

Hi Jon,

       There are two gain controls on Larry's boards. Close behind the first 
opamp, there are two pins about 1 cm high, 1mm square and they usually have 
black plastic shorting clip. For higher gains, this link should be placed on 
only one pin so that the circuit is left open. Then there some capacitors and a 
vertical potentiometer with an adjustment screw on the top (yellow in photo). 
This adjusts the gain from x1 to x10. Then you have a 14 pin DIL opamp and 
towards the output of the board a zero set potentiometer.

> Each channel has a two-pin jumper that controls the gain of the first 
> op-amp. With the jumper in, the gain of the board will be ~145 to ~1700. This 
> range should be used with sensors that have a high output voltage, like a 
> geophone. With the jumper removed, the gain range is ~600 to ~6000.

       Regards,

       Chris Chapman   
In a me=
ssage dated 2007/02/27, jonfr@......... writes:



I got new hardware from larry t=
oday and I was setting it up. I have

problems setting up the gain for Channel 1 (Z). I don't get it up as hig

as I want. This can be seen on my online plot now, when a earthquake

appears on E-W and N-S, it doesn't appear on Z.




Hi Jon,



       There are two gain controls on Larry's=20=
boards. Close behind the first opamp, there are two pins about 1 cm high, 1m=
m square and they usually have black plastic shorting clip. For higher gains=
, this link should be placed on only one pin so that the circuit is l=
eft open. Then there some capacitors and a vertical potentiometer with an ad=
justment screw on the top (yellow in photo). This adjusts the gain from x1 t=
o x10. Then you have a 14 pin DIL opamp and towards the output of the board=20=
a zero set potentiometer.



Each channel has a two-pin jump=
er that controls the gain of the first op-amp. With the jumper in, the gain=20=
of the board will be ~145 to ~1700. This range should be used with sensors t=
hat have a high output voltage, like a geophone. With the jumper removed, th=
e gain range is ~600 to ~6000.




       Regards,



       Chris Chapman  =20