But the bridge is capable of extreme accuracy and precision and allows comparison to high-accuracy standards. Q: Can’t you simply use an ohmmeter to measure resistance?Ī: Of course you can. (Image source: ) Fig 2: The bridge is sometimes drawn as a rectangle this is less intuitive than the diamond rendition although it is electrically identical. Fig 1: The classic Wheatstone bridge schematic has four elements arranged in a diamond pattern, with an excitation voltage, while the null reading is usually (but not always), taken across the midpoint. It is sometimes drawn as a square, Figure 2 (especially by CAD programs), but most engineers prefer the diamond shape which shows the functionality more clearly. The circuit can be used to compare an unknown resistance Rx with others of a known value. It’s an excellent example of how a simple and clever configuration not only has many applications but has extended its life into the world of modern electronics.Ī: In its basic form, it is a passive electrical circuit which is used to measure an unknown electrical resistance by ratiometric balance of legs (sometimes called arms) of a four-element “bridge circuit” with the unknown resistance as one of the legs, Figure 1. This FAQ will look at the circuit arrangement of this bridge, what it does, why it is still in wide use, and some additional useful variations of it. There’s still a viable place and need for old devices such as the transformer, solenoid, relay, and Wheatstone bridge. Although the electronics industry is relentlessly driven by advances in materials, components, and architectures, the “new” obviously also builds on the “old” and often still uses it, albeit in new guises.
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