SmartSeis
TM
Maintenance Manual
4
During initial set-up, check the cable connectors for debris (dirt, dust) on, or damage to, the
connecting surfaces, and firmly connect them to the seismograph. If the seismograph displays a
dead or noisy trace(s)
, there is likely a problem with the associated geophone or spread
cable. First, swap the spread cable connectors that plug into the seismograph and see if the
problem moves to a different channel. If the problem moves with the cable, the cable and/or
geophone are suspect.
Next check the geophone condition, its connection with the spread cable, and whether it is
planted in the ground. Also, try substituting a different geophone. After these tests, if the cable
is suspect, try reversing it or swapping it out.
If the problem persists on a single channel and does not move with the cables or geophones, it
could indicate that there is problem with the associated acquisition board. See
Section 2.2,
Replacing an acquisition board
.
An entire
set of 12 dead or noisy traces
may also be attributed to cable condition or a bad
board, as well as close cable proximity to a noise source. Check the externally connected
cables as described above. If the cables are not suspect, remove the seismograph chassis from
the yellow housing (see
Section 2.1, Internal seismograph access
) and check the cable
connections, starting with the panel connector(s), leading to the acquisition board(s).
You can try swapping the connections to the acquisition boards if you have a 24-channel
system. If the problem is still on the same set of channels, then it is likely that the acquisition
board is bad. Replace it if a spare is available, referring to
Section 2.2, Replacing an
acquisition board
.
If noise is the problem, shift the cabling to see if that changes the nature of the noise. If there is
a change, this would indicate an external noise source too near the cabling.
1.3 Triggering
The seismograph can be triggered by contact closure, contact opening, or signal input, such as
from a geophone. The input signal level should never exceed 5 volts.
If the system
fails to trigger
, test whether the hammer switch is broken by triggering it
connected directly to the seismograph, without the extension cable. To trigger, tap the end of
the brass cylinder on a table or hard object. The seismograph should trigger each time and not
false trigger prior to tapping of the cylinder. If there is no trigger, swap out the suspected
switch with a new one and retest it to confirm that it functions. If you are using another device
to trigger the seismograph, test it similarly for proper operation.
If the system still fails to trigger, check if the seismograph trigger circuitry is operational. Set the
trigger sensitivity to the midpoint at 50. Next, trigger the seismograph using the MANUAL
TRIGGER function in the OTHER menu.
