4.
High voltage power supplies: generally, the HVPS should float from power
line ground with the only ground being made at the preamplifier through the
high voltage connecting cable.
5.
Analyzer EMI: if the detector is located within about 6m (20 feet) of a
multichannel analyzer containing a ferrite core memory, it can receive EMI
(electro-magnetic interference). This is due to high memory core currents
during the memory cycle of the analyzer. The only practical cure for this
problem is to operate the analyzer in the “Live” Mode of accumulation. In
this way, the memory cycle only operates while no signal is being analyzed.
6.
Is the output of the spectroscopy amplifier and the input of the ADC fully
compatible? This may seem an obvious consideration, but it is commonly
overlooked. The shaping time constant as stated on the spectroscopy
amplifier is not the rise time of its output signal. In the case of a Model
2015A Amplifier, the time-to-peak of the AMP OUTPUT is 1.75X the
shaping time constant. Therefore, a 12
µ
s shaped pulse required 21
µ
sec to
reach full amplitude. Many analyzers will not handle this; instead of
analyzing the peak of the signal, they analyze a percentage of the rise time.
7.
Amplifier parasitic oscillations. If the cable connecting the front panel
outputs of the amplifier to the ADC exceed about 3m (10 feet) in length,
oscillations can occur. The cure is to use RG-62 cable (93 ohm impedance)
and terminate the ADC end of the cable with a 93.1 ohm metal film resistor.
Alternatively, the 93 ohm output impedance of the amplifier can be used
with no terminator.
SCA Operation
Setup
1.
Connect the INPUT of the 2015A to the ATTEN OUTPUT of a reference
pulser, such as the Canberra Model 1407.
2.
Connect the AMP OUTPUT signal to channel 1 of an oscilloscope. Connect
the SCA OUTPUT to channel 2 of an oscilloscope. Simultaneously observe
both outputs on the oscilloscope, or observe the AMP OUTPUT on a
multichannel analyzer. Set the oscilloscope vertical sensitivity for 5 V/cm
and sweep speed to 1
µ
s/cm.
3.
Set the 2015A controls as indicated below:
SHAPING:
2
µ
s
15
SCA Operation
Summary of Contents for 2015A
Page 1: ...Model 2015A Spectroscopy Amplifier Timing SCA User s Manual 9231694B 01 05...
Page 6: ...Notes iv...
Page 12: ...Internal Controls 6 Controls and Connectors Figure 4 Internal Controls...
Page 55: ......
Page 56: ......
