Which of the following best describes a 'dead weight tester'?

A 'dead weight tester' is primarily recognized as a device used for calibrating pressure gauges. This calibration process involves applying a known weight to a piston, which generates a specific pressure depending on the area of the piston. By using this method, the accuracy of pressure measuring instruments can be verified and adjusted as necessary. It provides a highly reliable standard for pressure measurement, making it essential in various industries where precise pressure readings are critical.

In this context, it's important to understand the other options. Measuring temperature involves different instruments such as thermocouples or thermometers. Electrical resistance is typically measured using an ohmmeter, not a dead weight tester. Insulating circuits relates to preventing electrical current flow and does not pertain to the function of this device. Thus, the primary role of the dead weight tester in calibrating pressure gauges distinguishes it as the correct choice.