specific physical load applied to the cell. This specific, equivalent load is the shunt calibration
value.
The advantage of using shunt calibration is that the final, registered load reading caused by
the shunt calibration at any time will be equivalent to a physical load on the cell equal to the
shunt calibration value, independent of the excitation voltage, input impedance, amplification
etc. used in the registration equipment.
12.3 Seismic Detector 86211
12.3.1 Key Features
High precision
Long term calibration stability
Very robust
Light weight
Weatherproof construction
Clamping magnet for easy mounting
Low impedance
Requires no power
12.3.2 Description
The DYNATEST SEISMIC DETECTOR 86211 (SD, also sometimes named “deflector”,
“deflection sensor” or “geophone”) is a very robust, high precision, light weight, seismic
velocity transducer in a sealed aluminium housing with an internal electrical shield. It has a
natural frequency of approx. 5Hz and ± 2mm available movement of the seismic mass.
The SD is delivered with a cable length of 5 m. A clamping magnet at the bottom of the
Deflector makes fixture to and removal from a deflector holder quick and easy.
The SD can only be used for the measurement of vertical movements with the clamping
magnet downwards and the mounting surface horizontal. If the Deflector is tilted, the
measuring range will be decreased, but the sensitivity will remain virtually unaffected.
12.3.3 Specifications
(SD vertical within 10 degrees, clamping magnet downwards, values typical at 25°C unless
otherwise specified):
Natural frequency: approx. 4.7 Hz
Output resistance: 375 ohms
Damping coefficient: approx. 0.7 (when connected to the Compact 15)
Available movement of seismic mass: 4 mm (total, i.e., +/- 2 mm from equilibrium
position)
Weight: 250 g (excl. cable)
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