First encounters
The Güralp 40T can be ordered with a option for automated “digital nulling”. See
section 3.4.4 on page 16 for more information and instructions for using this
function.
3.4.1
Adjusting the mass position offsets manually
The 40T has three potentiometers (“pots”) accessible within its casing, which should
be used to remove any DC offsets electronically:
1. Bring the instrument into 1 second response mode by applying a voltage
across the
Acc/Vel
and
Signal Ground
pins of the input. If you are using a
DM24, you can do this by sending a
CENTRE
command. If you are using a
Hand-held Control Unit, you should select
1 SEC VEL
from the
Velocity Select
switch.
2. Measure the vertical mass position output with a 10 V voltmeter (see
Chapter 6 on page 34 for pin-out details) or by selecting
MASS POS, V
from a
Hand-held Control Unit's
Display Select
knob. If using a HCU, also check that
the
Centring Select
knob is set to
OFF
.
3. If the vertical component needs adjusting, remove the cap on the lid which
protects the Vertical pot with a flat-bladed screwdriver.
11
Issue F - June 2019
