Chapter 3, OPERATING INSTRUCTIONS
3-2
3.2.05 Low-pass Filter
The amplifier includes an output low-pass filter with three settings of 100 kHz,
1 MHz, or 10 MHz, as selected by the
LOWPASS
slide switch. The filter has a roll-
off of 18 dB/octave with corner frequencies of 100 kHz ±15 kHz, 1 MHz ±150 kHz,
or 10MHz±1.5 MHz as indicated by the
100k
,
1M
, and
10M
switch settings
respectively.
3.2.06 Output Coupling
The output signal can be AC or DC coupled, as selected by the
OUTPUT
slide
switch. When AC coupled the low-frequency cut off frequency is 0.1 Hz.
Typically, the amplifier output coupling should be set to AC to optimize battery life,
unless a DC coupled output is specifically required. Also when applying a 50
output load to the amplifier (or any load less than 10 k
), the output coupling should
only be set to AC. Using DC output coupling with a 50
output load will cause the
battery charge levels to become imbalanced, shortening their useful life.
3.2.07 Output Connector
The amplified signal is connected to the output BNC connector. The output
impedance is 50
with short-circuit protection.
3.3 Operating the Model 5402
3.3.01 Introduction
The amplifier is powered from the self-contained batteries, which can be recharged
from an external 9 V DC power source, such as the
SIGNAL RECOVERY
Model
PS0112 (see Appendix B). The signal to be amplified is applied to the
INPUT
connector, and he amplified signal is available at the
OUTPUT
connector.
3.3.02 Signal Gain & Output Voltage
The gain selector accurately sets the gain to the indicated level. The output is
guaranteed not to clip for output voltages of up to a minimum of ±2.5 V into a high
impedance load, but with fully charged batteries larger output voltages of up to
±4.0 V are possible.
3.3.03 Output Filtering
If measuring very low frequency signals (for example below about 10 Hz), the
OUTPUT
coupling must be set to
DC
. At frequencies above 10 Hz when rejection
of any DC signal on the output is required, the switch can be set to
AC
.
If using the higher gain settings (10M and above) and if the signal frequency is low
enough, then setting the
LOWPASS
filter to
1M
or
100k
can give a useful reduction
in the overall level of system noise. This filtering can be useful when using gains of
100M
or
1G
, which by their nature will produce a noisier output. If, however, the
widest bandwidth is required then set it to
10M
.
3.3.04 Battery Operation
The internal batteries will power the Model 5402 for up to 48 hours, depending on
