What is Parallax Error in Differential Pressure Gauges and How to Avoid It?

Posted on: 08/07/2025

What is parallax error?

Parallax error occurs when the pointer of a device appears to indicate different readings depending on the viewing angle – for example, when viewed from the side instead of directly from the front. This happens due to the distance between the pointer and the scale – since they are not on the same plane, readings taken at an angle may be inaccurate.

When might you encounter parallax error during measurement?

Dial-type devices such as pressure gauges or thermometers are prone to parallax error if viewed from the left or right side rather than directly from the front.

How to correct or avoid parallax error?

The simplest way to avoid parallax error is to read the measurement directly from the front of the device. The high-accuracy Magnehelic® differential pressure gauge comes with a standard mirrored overlay to eliminate parallax error during measurement. When taking a reading, make sure the pointer aligns perfectly with its reflection on the mirror – this ensures the most accurate reading possible.

High Accuracy Magnehelic® Differential Pressure Gauge, Series 2000-HA