Manual

9 4
PCB Components 767E/01 PCB REV-01 contd...
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Ref Designator Value
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RESISTORS
R36 200K(390K),1/4W,0.1%,MFR
R37 10M(20M),1/4W,0.1%,MFR
R38 10M(20M),1/4W,0.1%,MFR
R39 200K(390K),1/4W,0.1%,MFR
R40 100K,1/4W,5%,MFR
R41 100K,1/4W,5%,MFR
R42 11K,1/4W,5%,MFR(SEL-W)
PRESETS
PR5 1K,VER, M/T BOURNS (3296-W)
PR6 10K, VER, M/T BOURNS (3296-W)
PR7 10K, VER, M/T BOURNS (3296-W)
PR9 2K,VER, M/T BOURNS (3296-W)
PR10 2K,VER, M/T BOURNS (3296-W)
PR11 10K, VER, M/T BOURNS (3296-W)
PR12 10K, VER, M/T BOURNS (3296-W)
PR13 10K, VER, M/T BOURNS (3296-W)
PR14 10K, VER, M/T BOURNS (3296-W)
PR15 2K, VER, M/T BOURNS (3296-W)
CAPACITORS
C1 NOT USED
C2 NOT USED
C3 NOT USED
C4 NOT USED
C5 10uF,35V,EL,RAD
C6 10uF,35V,EL,RAD
C7 47uF,50V,EL,RAD
C8 10uF,35V,EL,RAD
C9 10uF,35V,EL,RAD
SECTION - 4
CIRCUIT DESCRIPTION
The Model 1522 Digital Wattmeter measures true rms
values of voltage across the load, the load current and
the power consumed by the load (real power in Watts ).
Main PCB (ref: WD 76XX-01)
The line voltage is sensed at the "VIN H" and "VIN L"
terminals. It is attenuated by a factor of approx.50 and
connected to the inputs of IC16 (TL071). The circuit
associated with IC16 converts the "floating" signal to a
"single-ended" signal. The waveform on test point TPV1
is a scaled version of the line input voltage. This signal
is connected to IC14 (AD736), which is a RMS - DC
converter. The output at pin 6 of IC14 is a DC voltage
proportional to the input line voltage. Attenuator network
R31, PR10 (VCAL), and R33 is used to attenuate this DC
voltage by a factor of approximately 2. The DC voltage on
TPV2 should be exactly 1/100th the RMS value of the
input line voltage.
The load current is sensed by a "shunt" resistor, R16,
in the neutral return path. The voltage across R16 is
connected to the inputs of IC9 (TL071). The circuit
associated with IC9 converts the "floating" signal to a
"single-ended" signal. The waveform on test point TPI1
is a scaled version of the load current. This signal is
connected to IC12 (AD736), which is a RMS - DC
converter. The output at pin 6 of IC12 is a DC voltage
proportional to the input load current. The resistor
network R30, PR9 (ICAL), and R28 is used to amplify this
DC voltage by a factor of approximately 4.0. The DC
voltage on TPI2 should be adjusted to 200mV for a load
current of 10 A. IC15 (AD633) is an analog multiplier.
Signals from TPV1 (corresponding to the line voltage) and
TPI1 (corresponding to the load current) are connected
to input pins 4 and 2 resp. of IC15. The output on pin
7 corresponds to waveform of the instantaneous power
consumed by the load.