Model 815 is a high-sensitivity, variable capacitance accelerometer which measures static acceleration and low-frequency vibration. 815 is a capacitive accelerometer family utilizes a silicon Micro-Electro-Mechanical System (MEMS) variable capacitance sensing element. The sensing element consists of a very small inertial mass and a flexure element cantilever positioned between two plates. As the mass deflects under acceleration, the capacitance between these plate changes. AC excitation and synchronous amplitude demodulation circuitry contained in the accelerometer's internal signal conditioner provides an analog output signal proportional to the applied acceleration. This output signal is scaled as a current which is proportional to the applied acceleration. The output signal format is 4~20mA loop current. The accelerometer is powered by a single regulated supply between 12 to 30 Vdc. The sensing element and electronics are contained in a tough housing with an integral cable terminated by pigtails or specified connector. Signal ground is isolated from the test object that benefit by the anodized aluminum housing. The accelerometer can be mounted by M6 metric screw or adhesive. 815 is well-suited for a wide variety of high speed train applications requiring precision measurements and reliability package