Brass Gauge style (PSIg) Pressure Sensors AEM offers brass PSIg sensors in 15, 100 and 150. Gauge style pressure sensors reference pressure above atmospheric pressure. When exposed to atmospheric pressure, gauge style pressure sensors will read 0 psig. Gauge style pressure sensors are commonly used for oil pressure, fuel pressure, brake pressure, nitrous pressure etc. Which Pressure Sensor is right for you? There are many different tools that can be used for measurement, but the degree of accuracy is dependent upon the tool. For example, a ruler can measure distance with a good degree of accuracy, but for a more precise measurement a caliper should be used. The difference between a brass pressure sensor and a stainless steel pressure sensor is similar if we think about it in these terms: Brass Pressure Sensor = Ruler Use a Brass Pressure Sensor where you need a good reference to what pressure is being seen. Example: Brass Pressure Sensor used for a Boost Gauge - Reference/Information for knowing manifold pressure, not for ECU calibration. Stainless Pressure Sensor = Caliper Use a SS Pressure Sensor where you need exact details of the pressure. Example: MAP Sensor information for the ECU - Calibration/crucial information for the ECU.