You press on the brake pedal and your car stops. We take this for granted because brake systems are extensively tested before a car is put into production. Brakes are basically hydraulic systems that translate the force applied to the brake pedal into pressure that moves the brake pads toward the rotor. Measuring the hydraulic pressures required to stop a vehicle is an important part of brake system testing. Transducers used to make this measurement must have several important attributes.

Brake testing involves making measurements on vehicles that are moving. This testing is often done in climatic extremes. Transducers that measure brake system pressures must be mounted under the hood, near the brake cylinders and hydraulic lines. This means the transducers are subject to shock and vibration, as well as heat from the engine. The transducer must be small enough to fit in the close confines under the hood, and be rugged enough to withstand shock and vibration. Loss of the transducer pressure boundary in this rugged environment could cause brake system failure.

The amount of fluid required by the transducer to reflect the brake hydraulic pressures must be minimal so as not to distort system performance. The transducer must have a bleed port so that any air in the brake hydraulic system can be removed. In addition, transducer error as a result of ambient temperature changes must be minimized to obtain the most accurate pressure measurements.