DESCRIPTION
The Model 1221 is a low-cost, integrated accelerometer for use in zero to medium frequency instrumentation
applications that require extremely low noise. The 2g version is ideally suited for seismic applications. Each
miniature, hermetically sealed package combines a micro-machined capacitive sense element and a custom
integrated circuit that includes a sense amplifier and differential output stage. It is relatively insensitive to
temperature changes and gradients. Each device is marked with a serial number on its bottom surface for
traceability. An optional calibration test sheet (1221-TST) is also available which lists the measured bias, scale
factor, linearity, operating current and frequency response.
OPERATION
The Model 1221 produces two analog output voltages, which vary with acceleration as shown in the figure below.
The outputs can be used either in differential or single ended mode. Two reference voltages, +5.0 and +2.5 volts
(nominal), are required; the output scale factor is ratiometric to the +5 volt reference voltage, and both outputs at
zero acceleration are nominally +2.5 volts. The sensitive axis is perpendicular to the bottom of the package, with
positive acceleration defined as a force pushing on the bottom of the package.

Number of axes : single-axis
Technology : MEMS