AD7730 application question re 6-wire loadcell

Document created by analog-archivist Employee on Feb 23, 2016
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I have a question related to the AD7730 Bridge Transducer ADC. In our
application we need to use both channels to connect two bridges of the same
type, and both of the bridges are in a six-lead configuration. I have a
question how to connect the reference inputs REF IN(+) and REF IN (-) terminals
in such case to obtain best results and take advantage of the IC performance.


When using a 6-wire loadcell, the 2 SENSE wires from the loadcell need to be
used as the reference to the ADC. So, when loadcell 1 is selected, its SENSE
pins need to be used as the reference to the AD7730. Similarly, when loadcell 2
is selected, the SENSE wires of loadcell 2 need to be connected to the REF pins
of the AD7730. To do this, an external mux or switch is needed so that you can
switch between the SENSE pins of loadcell 1 and loadcell 2.

The AD7190 could be used in place of the AD7730 if you are using DC excitation.
The AD7190 has 2 reference inputs – REFIN1 and REFIN2. Therefore, the SENSE
pins of each loadcell could be connected permanently to the AD7190. You would
then only need to select the appropriate reference source (REFIN1 or REFIN2).