Bird Technologies 4314C - Manual (Page 18)

6
Peak Power Operation
The Model 4314C is designed to measure peak power in addition to average power.
When the toggle switch is placed in PEAK mode (Figure 3 on page 7), battery power
energizes the amplifier system. If the AC adapter is being used, it energizes the relay
and disengages the batteries.
The battery test circuit is energized when the push button switch is pressed. If
the voltages of the two 9 V batteries are within the limits necessary to properly
operate the amplifier circuit, the pointer of the meter deflects beyond the bat-
tery test mark on the meter scale. If the pointer fails to reach the mark, the bat-
teries need replaced. Replacement of both batteries simultaneously will assure
that sufficient battery power will be available for extended periods of time (see
“Maintenance” on page 21). If the push button is pressed continuously for a
length of time exceeding 10 seconds, the load will be disconnected from the bat-
teries. This feature allows the batteries to maintain a charge even if the wattme-
ters’s battery test button had been mistakenly pressed for a long period of time.
After the load has been disconnected, the battery test reading will no longer be
accurate.
The internal amplifier circuit is designed to provide current to the meter. The
meter current indicates, at a steady state, the peak of the power applied to a
load resistor at the input of the peak detect circuit. This input load resistor
exactly matches the resistance of the meter, thus the existing circuit in the Ele-
ment is loaded with the same current as the average reading mode (Figure 2 on
page 7).
When the toggle switch is moved from CW to PEAK, the DC input that is normally
applied to the meter is interrupted and is applied instead to an input load resistor.
This input is then routed through a circuit that first amplifies and then holds the
peak envelope power level detected. This peak power level is converted back to
the proper level for the meter and is then displayed on the meter. Two variable
resistors provide both zero and gain calibrations of the amplifier circuit.
The peak hold circuit continues to maintain the reading of the meter even
though the peak of the pulse is no longer applied to the amplifier circuit. Only
the peak power is indicated even though there is a wide fluctuation of input
power. Because of a small amount of leakage designed into the peak hold circuit,
there will be a decay that limits the time the amplifier system will retain its out-
put level. As the circuit decays, the meter will return to zero if no additional
pulses are received at the input load resistor.