There is no point reaching for a calculator that cannot show its working. This one starts from input voltage (v), r1, r2, r2, r3, r3, rx and bridge voltage (vg) and reports r1 and rx, so you can see how each answer follows from the numbers you entered.
What Is the Wheatstone Bridge Calculator?
This wheatstone bridge calculator is for the kind of problem where you know the physical quantities but not the number you need. It turns input voltage (v), r1, r2, r2, r3, r3, rx and bridge voltage (vg) into r1 and rx.
Physics calculations go wrong in predictable ways, usually through mixing units or dropping a digit. Work through the result one step at a time and check that the figures are the size you would expect at each stage.
How the Wheatstone Bridge Physics Works
The relationship is applied step by step, and each step is a standard piece of physics rather than a single opaque formula. That means you can check the intermediate values against what the theory predicts, which is usually faster than checking only the final answer.
Keep every value in the same unit system throughout the calculation. Mixing metres and feet part way through is the single most common reason a correct formula gives a wrong answer.
Units, Assumptions and the Limits of the Model
The calculation assumes ideal conditions: no air resistance, no heat loss, and dimensions that do not change while you work. Those assumptions are reasonable for most classroom and engineering estimates, and unreasonable for anything more precise.
Where a value is a rate, it has to be quoted for the same period as everything else. A per-hour figure cannot be combined with a per-day figure without converting one of them first.
A Worked Example
Working through an example, with input voltage (v) set to 10, r1 set to 5, r2 set to 2, the calculator returns r1 of 10, and rx of -5.50239. Substitute your own figures and the same steps produce the same kind of answer.
Frequently Asked Questions
What do I need to work out r1?
Enter input voltage (v), r1, r2, r2, r3, r3, rx and bridge voltage (vg). The calculator then works through the relationship and reports r1 and rx.
What does the wheatstone bridge actually calculate?
It takes input voltage (v), r1, r2, r2, r3, r3, rx and bridge voltage (vg) and converts them into r1 and rx using the standard relationship for this problem. Each step is applied in turn, so every output is traceable back to the numbers you typed in.
How should I enter input voltage (v)?
Use the value you actually have, in the unit shown next to the field. Enter every value in the same unit system. The calculator assumes the figures you supply are consistent, so it cannot correct a mistake that happens before the calculation starts.
Why does a small change in one value move the answer so much?
That happens when an output depends on a ratio, because dividing by a small number magnifies any change in it. Check the units first, then check whether the value you entered is in the range the relationship was designed for.
Do I have to fill in every field?
Only the fields a particular result depends on. If you leave one blank, the results that need it simply show a note instead of a number, and everything else still works.