Tektronix DM 5010, Инструкция по эксплуатации

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Theory of Operation—DM 5010
ATTENUATOR <$>
The input signal to be measured passes through a resis­
tive attenuator network that prescales the analog signal to
fall within the input circuitry’s dynamic range. Attenuation
factors of 1 and 100 are controlled by closing contacts of
relays K1527, K1425, and K1525 as shown in Fig. 4-1 and
Tables 10-2 and 10-5 in the pull out pages.
OVERVOLTAGE PROTECTION AND FUNC­
TION SWITCHING <J>
All measurement modes of the DM 5010 require that
some type of conditioning be performed on the input signal
before an A/D conversion is performed. In each case, the
input conditions are converted to a representative de volt­
age level by the appropriate conditioning circuitry and are
then applied to the DCV Signal Conditioner where some
range-dependent gain factor is applied to the signal. This
resultant prescaled signal is the basis for all A/D conver­
sions and, along with the various mode, attenuation, and
gain factors set by the microprocessor, represents the input
conditions.
This stage selects the appropriate conditioning circuit
output and routes it to the DCV Signal Conditioner input. It
also provides overvoltage protection should these signals
exceed the specified input range.
A simplified schematic of the Overvoltage Protection and
Function Switching stage appears in Fig. 4-2. Each of the
FET switches connects either an individual function or the
high quality ground reference to the DCV Signal Conditioner
when closed. Refer to Tables 10-2 and 10-5 in the pull out
pages for mode-dependent function and range switch
settings.
Transistors Q1327 and Q1323 connected as diodes pre­
vent the input voltage applied to FET switch Q1319 from
exceeding « + 23 volts and —23 volts, respectively. Similar­
ly,
transistors Q1321 and Q1322 prevent the output voltage
of the Ohms Converter from exceeding the same voltages.
Fig. 4-1. Attenuator.
ADD JAN 1982
4-5