Screening Services & Training  LLC                                                                                                                                      Last Update 10/28/2015
25092 Natama Ct                                                                                                              Based upon a procedure written by Screening Systems, Inc.
Laguna Hills, CA  92653-5607

How to:  Calibrate the Single-Board Interface SCM-100 Accelerometer Electronics using the Internal Signal Generator.

This procedure applies to systems manufactured by Screening Systems, Inc. that use the SSC-2000 model vibration controller driving the single board,  or two board, SCM-100 interface.

To use the internal signal generator to calibrate the SCM-100 accelerometer electronics requires the internal signal generator output be within specifications.  To verify the accuracy of the internal signal generator, connect an external sinewave function generator (FG) to the Control Accelerometer 1 (X1) BNC accelerometer input connector.  Set the FG to 100.0 +/- 0.5 mVrms at 464 +/- 10 Hz. sinewave output.

Perform the calibration of the SCM-100 (X1) accelerometer electronics by selecting Configure > Calibrate > Accelerometer (Old style if asked to select a style) from the main menu bar on the screen. This will bring up the Vibration Calibration pop-up window.   Left mouse on the “Input Channel” bar and select the top most selection, “Control Accelerometer 1 (X1)”.  Set the “Input Level” to 10.00 GrmsLeft mouse on the "START (F2)" button. When the Seconds down-counter reaches “0”,  write down the value in the X1 Offset window at the upper left corner of the pop-up window.

Now select "Internal Calibration Signal (All Channels), the bottom most selection from the Input Channel bar.  Verify/set the “Input Level” to 10.00 GrmsLeft mouse on the "START (F2)" button. When the Seconds down-counter reaches “0”,  write down the value in the "Int" window located two windows to the right of the Input Channel bar.  Compare this value with the number written down in the previous steps.

 If both values are within +/- 1.0% of each other, the internal signal generator is within specifications and the accelerometer electronics calibration data just obtained may be used.  In this case,  left mouse on the "USE INTERNAL (F4)" button to copy the Offset value to the offset boxes of all Control, Averager and Auxiliary readings.  Read and record the offset value then select "EXIT (F1)" and "YES" to save the changes.  This completes the calibration procedure.

If both values are not within +/- 1.0% of each other, the internal signal generator is not in calibration and its settings must be adjusted.  This is accomplished by removing the cover from the SCM-100 and allowing the SCM-100 to warm up for 30 minutes.  Using NIST traceable instruments check and adjust the following parameters between pins 10 of U19 and signal ground on the Analog board.

Check that the amplitude of the signal is 100.0 +/-0.5 mV rms.  Adjust potentiometer R37 for the amplitude.
Check that the frequency is 464 +/-10 Hz.  Adjust potentiometer R40 for the frequency.

After reinstalling the cover on the SCM-100, starting the SSC-2000 program, and warming up the system for 30 minutes, perform the internal calibration of the SCM-100 accelerometer electronics by selecting Configure > Calibrate > Accelerometer (Old Style if asked to select a style) from the main menu bar on the screen.  This will bring up the Vibration Calibration pop-up window.

Left mouse on the “Input Channel” bar and select the “Internal Calibration Signal (All Channels)” option.  Set the “Input Level” to 10.00 GrmsLeft mouse on the "START (F2)" button. When the Seconds down-counter reaches “0”, left mouse on the "USE INTERNAL (F4)" button to copy the Offset value to the offset boxes of all Control, Averager and Auxiliary readings.  Read and record the offset value then select "EXIT (F1)" and "YES" to save the changes.

This completes the calibration procedure.

For technical assistance contact Screening Services & Training LLC  via e-mail.  scrserv@cox.net

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