CybraTech (2000) Ltd.
SOC-3000/i Scale-On-Chip
ASIC
Technical Specification
Revision B
Page 75
July, 2002
SOC-3000 HARDWARE DESIGN CONSIDERATIONS AND
PERIPHERAL INTERFACE CONNECTIONS
Load Cell Interface
The SOC-3000 supports a wide range of load-cell connection configurations, each based on
various combinations of the following connection options:
•
4-wire or 6-wire interface
•
Up to eight load cells connected in parallel
•
Load cell impedance range of 350 to 1000 ohms
Individually and in combination, these connection options enable the SOC-3000 to function
on a wide range of application platforms, each having different power consumption and
system configuration requirements, while using the same electronic hardware.
4-Wire and 6-Wire Interfaces
The SOC-3000 interface to the load cell carries the following electrical signals:
•
SIG + (Signal Input +)
•
SIG – (Signal Input –)
•
SEN + (Excitation voltage / Sense input +)
•
SEN – (Excitation voltage / Sense input –)
A typical 4-wire load-cell connection, in which the distance between the load cells and the
SOC-3000 chip is small, as in a standard retail scale, is shown in Figure 26.
However, in platforms requiring long wires between the load cell and the electronic
hardware, such as weighing bridges, the voltage drop over the cables is significant and affects
accuracy.
The 6-wire interface eliminates this error factor by using the sense wires, as shown in Figure
27. The sense wires serve as a reference for the ADC converter, thus eliminating the voltage
drop over the long excitation-voltage wires.
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