(5) When the Model 540B is operated in the SHUNT mode, no protection is
provided for either the Model 540B thermocouple or for the current shunt.
necessary to exercise caution when operating in this mode to prevent damage to the
Model 540B block diagram
i. Figure 2-5 is a simplified representation of the search circuit.
Attenuator components shown are those selected when the range switch is in the I-V
The search circuit is composed of three basic elements; the search-
compensated attenuator, search amplifier, and percent input meter.
(1) The search-compensated attenuator is compensated to equalize the output
of the search amplifier in order to give the percent input reading a favorable
is accomplished with R310. High frequencies are calibrated with C305. CR301 and
CR302 rectify the amplified AC and capacitors C303 and C304 filter the resultant DC
voltage for application to the PERCENT INPUT meter.
used in DC SEARCH and a path is provided by the MODE switch to apply DC directly to
the meter from the attenuator.