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Topic: Reading Small voltages (Read 4 times) previous topic - next topic

Papa G

#20
Nov 30, 2012, 05:43 pm Last Edit: Nov 30, 2012, 05:55 pm by PapaG Reason: 1
While the circuit is indisputably a Wheatstone bridge, when naming strain gauge configurations one considers the number of active arms. The OP's configuration is called a half bridge circuit by those familiar with the terminology and can be verified by reading the data sheet for a common strain gauge amplifier from Analog Devices http://www.analog.com/static/imported-files/data_sheets/5B38.pdf

edit: fixed link

retrolefty


While the circuit is indisputably a Wheatstone bridge, when naming strain gauge configurations one considers the number of active arms. The OP's configuration is called a half bridge circuit by those familiar with the terminology and can be verified by reading the data sheet for a common strain gauge amplifier from Analog Devices 5B38.pdf


Your link is broken, maybe it's only a half or quarter link?  ;)

Papa G



While the circuit is indisputably a Wheatstone bridge, when naming strain gauge configurations one considers the number of active arms. The OP's configuration is called a half bridge circuit by those familiar with the terminology and can be verified by reading the data sheet for a common strain gauge amplifier from Analog Devices 5B38.pdf


Your link is broken, maybe it's only a half or quarter link?  ;)


lol, you're right. Maybe only 1/8 link.  :) Fixed.

retrolefty

#23
Nov 30, 2012, 06:08 pm Last Edit: Nov 30, 2012, 06:19 pm by retrolefty Reason: 1
Well that doesn't change my definition of what a full bridge configurations is or is not. The Figure  3  5B38 Input Field Connections picture in that doc clearly shows the different configurations and how many elements are used. A full bridge uses four elements regardless of which of the four are variable or not. The other two are simply set up as a simple two element voltage divider. I would never call a simple two element resistive voltage divider a 'bridge circuit', half, quarter, or otherwise.

The OP showed us a crude drawing of a four element bridge with two fixed resistors and two variable load cell resistors (disregarding his attempt at adding a null adjustment pot), wired in a full bridge configuration, end of story.  ;)

I think possibly what AD and you and the OP are trying to state is that load cells come in several styles where the load cell itself makes up either all four elements of a full bridge (four output wires) or just two (three output wires provided) or one of the elements (two output wires provided) needed to be wired up to the rest of the input circuit to complete a full bridge configuration. Hows that for a compromise ?  ;)

Lefty

Papa G


Well that doesn't change my definition of what a full bridge configurations is or is not. The Figure  3  5B38 Input Field Connections picture in that doc clearly shows the different configurations and how many elements are used. A full bridge uses four elements regardless of which of the four are variable or not. The other two are simply set up as a simple two element voltage divider. I would never call a simple two element resistive voltage divider a 'bridge circuit', half, quarter, or otherwise.

The OP showed us a crude drawing of a four element bridge with two fixed resistors and two variable load cell resistors (disregarding his attempt at adding a null adjustment pot), wired in a full bridge configuration, end of story.  ;)

Lefty


That particular module comes in several factory configurations in which the bridge is completed internally depending on the number of active external arms.

Here is another article http://www.transducertechniques.com/wheatstone-bridge.aspx that explains the terminology pretty well. You are welcome to use what ever terminology you please.

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