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Current i
At half
scale
deflection
/
Voltage e
At full
scale
deflection
Fig.5.6. Current- Voltage characteristic of R.M.S. detector
schematic ( Fig.5.5) implies, since it is in fact made up of a number of
averaging networks which give averaging times ranging from 0.1 to 100 sees.
and includes time constants which give "Fast" and "Slow" meter response
characteristics.
The averaging capacitors in the RMS Rectifier of the 2010 are all inter-
connected using FET gates which may be controlled from either the 8 & T
programmes or the EFFECTIVE AVERAGING TIME switch of the 2010.
This permits automatic as well as manual selection of averaging times. The
gates allow all the averaging capacitors in the circuits to charge to the level
of the RC network selected. This does not alter the averaging time of the
selected network, but does prevent it from discharging unnecessarily and
producing a temporarily inaccurate output or meter reading when a longer
averaging time is selected.
To obtain the widest possible dynamic range for the RMS Rectifier, two
attenuators are employed in the RMS circuit. These are operated auto-
matically via a Switching Circuit which is triggered when the signal level is
higher than that corresponding to 20 dB below FSD (Full Scale Deflection).
45
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