Teac GX-1, Instruction Manual

Page: 101 / 122

Amplifiers
4-34
Like the charge amp AR-GXCH, the AR-GXPA connects to an accel-
eration transducer that uses the piezoelectric effect; however, the AR-
GXPA connects to a transducer that has a built-in preamp to convert
the charge to voltage and lower the circuit resistance. The AR-GXPA
provides a constant current source (0.5 mA, 3 mA, and 5 mA) to this
preamp. If this constant current source is not provided, functionality is
the same as the DC input amp AR-GXDC.
The units for the input range are not G nor m/s 2 ; rather they are volts.
For example, when using a sensor that outputs 10.10 mV/G and mea-
suring up to 100 G, select 1 V for the range. In this situation, to record
in G units, use Change Unit to specify 0.0101 V = 1 G; and to record
in m/s 2 units, use Change Unit to specify 0.0101 V = 9.81 m/s 2 .
■
Filters
Analog Filter
The analog filter is an 8th order Butterworth low-pass filter (–48
dB/oct). The cutoff frequency can be selected independently of the
sampling frequency. To prevent aliasing, the cutoff frequency must be
set to 50% or less of the sampling frequency.
Digital Filter
The digital filter using a DSP can attenuate from 40% of the set sam-
pling frequency. The digital filter is not functional at sampling fre-
quencies of 200 kHz, 100 kHz, and 50 kHz.
■
Calibration
Zero and gain self-calibration using a DSP is performed whenever
power is turned on, and whenever the input range or the sampling fre-
quency is changed. The signal used for calibration is built into the
amp.
DC/ICP Input Amp (AR-GXPA)