Often it is not practical or affordable to
purchase a hand held data collector to perform spectrum analysis on your
vibration signals. A less expensive way around this is to wire an
accelerometer to an oscilloscope. An accelerometer requires voltage (between
18 and 30 VDC) at a constant current. The constant current is achieved with
a Constant Current Diode (CCD) placed inline between the + pole of the power
supply and accelerometer signal wire. The CCD should be around 2-6 mA (STI
uses a 4.4 mA CCD in our electronics). A 2 mA CCD is appropriate for very
short accelerometer cable length, and a 4.4 - 6 mA CCD is preferred for
longer cable runs. CCDs are available from Motorola
and Siliconix (4 mA Part # 1N5312 and J510 respectively)
