Avery Berkel CX20 SERIES, Руководство по обслуживанию

Страница: 35 / 353

2 — General and Technical
2–13 CX20/CX30/CX34 Service Manual
2.2 Electrical Description
The unit is powered by a mains electricity supply, which is transformed, rectified
and smoothed by a power supply unit. The power supply unit distributes the
derived power supplies to the main PCB through a cable loom terminated by a
multi–pin plug. Any external power supply requirements (such as when
powering an external data network) are provided by a connection from the
main PCB. When fitted, the comms PCB also provides a local power supply for
the network.
The transducer is a strain–wire type connected through a local PCB on the
transducer to the A/D PCB. The A/D PCB converts analogue data received
from the strain–wires into digital form. The resistance of the strain–wires
changes according to the strain placed upon them (caused by physical distortion
of the transducer shell), and this change of resistance is detected by the A/D
PCB. The A/D PCB generates a digital equivalent of the analogue input for use
by calculation circuitry on the main PCB.
The main PCB derives a calculation of the load weight, by reference to firmware
which determines the units of measure (Imperial, metric, or other according to
customer choice). The load weight data is passed to the display driver and to
the microprocessor. The load weight is displayed on both customer and vendor
displays.
The main PCB scans the keyboard for input. If a Price Look Up (PLU) is
entered, the microprocessor acquires the price per weight data from memory
(which is backed–up by a battery on the main PCB). The PLU data, which
includes price per weight and goods description, is passed to the display driver
and to the microprocessor. The price per weight or item price data and the
goods description is displayed on both customer and vendor displays (LCD on
vendor side – CX20 only).
The microprocessor calculates the load price by reference to the load weight
and PLU data, and passes the load price to the display driver. The
microprocessor also passes operator–prompt information to the display driver.
On the CX20, the display driver displays the load price on both customer and
vendor displays, and also displays operator–prompt information in
alpha–numeric form on the LCD. On the CX30 and CX34, the display driver
transmits both the load price and operator–prompt information to both customer
and vendor displays. It also passes a discrete signal within the display data
which is interpreted by the customer display to suppress operator prompt data
from that display.
The microprocessor waits for the transaction to be accepted, modified, or
cancelled: this is signalled to the microprocessor by further keyboard input or
can be automatic. Assuming that the transaction is accepted, the
microprocessor logs the transaction to a cumulative table of transactions. It
then transmits a selection of data to the printer driver which is situated on the
main PCB.
The printer driver, on receiving transaction data from the microprocessor,
translates the data by reference to firmware stored on the main PCB. The
firmware formats a printable entry, to include character–composition and page
size data, and transmits the formatted data to the printer assembly.
In label mode, when transaction has been accepted (automatic or keyboard
input), the printer prints a label and then advances the label roll ready for the
next label operation: transaction is complete.