The Endevco® Model 2270 primary comparison calibration standard accelerometer is a combination standard accelerometer and calibration fixture used for performing comparison calibrations of other accelerometers. The extremely high stability and very flat frequency response of the accelerometer is achieved through the use of sensing elements made of Endevco P-10 crystal material. The Model 2270 has a 1/4-28 tapped hole 0.5 inches deep for attaching units under test. Accessory bushings are provided to mount accelerometers that use 2-56, 6-32, or 10-32 sizes. Additional adapters with 4-40, 4-48, 8-32, and metric M3x0.5 threads are available. Signal ground can be switched from grounded to isolated at the user’s option by means of a knurled nut on the output signal receptacle.