PM9109BF
8.
Tariff, Scroll and Reset Functions
Tariff Selection
A dual DIP switch provides the user with the facility to set the active tariff register
in which consumption will be accumulated.
The active register is indicated on the LCD.
Scroll Facility
The 4 registers may be sequentially displayed by activating the scroll button. The
contents of the register selected for display is retained on the display for a period
of 10 seconds, provided that the push button is not activated during this period.
After the 10 seconds has elapsed, the display defaults to the "active" register
defined by the status of the tariff DIP switches.
The register selected for display via the scroll button is indicated by the relevant
announciators.
Reset Function
By pressing the Reset button the contents of the RAM of the SA9109B device is
set to the default conditions.
Jumpers J8, J9 and J10 must be removed to use this feature.
It is strongly recommended that the provision of this facility is not made available
on production meters.
9.
Circuit Description
The Application Circuit (Figure 2) shows the components required for a power
metering application, using a shunt resistor for current sensing. In this application
the circuitry requires a +2.5V, 0V, -2.5V DC supply.
The most important external components are:
C
1
and C
2
are the outer loop capacitors for the two integrated oversampling A/D
converters. The value of these capacitors is 560pF.
The actual values determine signal to noise and stability performance. The
tolerances should be within ± 10%.
C
3
and C
4
are the inner loop capacitors of the A/D converters. The optimum value
is 3.3nF. The actual values are uncritical. Values smaller than 0.5nF and larger
than 5nF should be avoided.
R
2
, R
1
and R
SH
are the resistors defining the current level into the current sense
input. The values should be selected for an input current of 16µA
RMS
into the
SA9109B, at rated line current.
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SAMES [ SAMES ]
