🔍 Key Concepts

• Parallax error when reading instruments • How to align your eye with a pointer and scale • Difference between reading a liquid column (like a mercury barometer) versus an aneroid barometer with a pointer

💭 Think About

• Think about what happens if your eye is not lined up with the pointer and the scale. Will the reading appear higher, lower, or accurate? • Which eye position makes the pointer look like it is exactly on one mark, rather than between two, no matter which side you move your head? • Consider how you are taught to read other pointer instruments (like an engine gauge or compass repeater). Where do you place your eye to avoid parallax?

✅ Before You Answer

• Identify which options would clearly cause parallax error (reading too high or too low depending on viewing angle). • Remember that an aneroid barometer uses a pointer and dial, not a visible liquid meniscus. • Confirm which choice positions your eye so the pointer and its scale mark are in the same line of sight.