Hi all,

  Here is the procedure I use to calibrate my mini-Lehman type sensor.  Does 
anyone have any comments?

Bob McClure

------------------------------
1. Set up limit stops on the pendulum so that it can be displaced over a 
known and fixed number of millimeters at its radius of gyration.

2. Connect the sensor directly to the A/D, and log data as you move the 
pendulum gently back-and forth a few times between the stops.  Record at a rate 
that gives a reasonable number of samples for the time taken to move between 
stops.  Do not move so fast that you exceed the voltage range of the A/D, 
otherwise you won't get valid data, and you might even blow out the A/D.  Also, verify 
that the resistance of the sensor coil is low compared to the input impedance 
of the A/D.

3. Make a WinQuake event file out of the data.

4. Use WinQuake to integrate the data.  You should see the actual 
displacement versus time, measured in counts.  Measure the peak-to-peak displacement in 
counts.

5. Scale the count measurement to what you would have obtained for one 
centimeter of motion.  If you used 5mm of displacement, for example, you would 
multiply your count estimate by two.

6. Multiply the scaled counts by the voltage gain setting of the amplifier 
you normally use.

7. Take the inverse of the number obtained in step 6.  This is the number you 
should enter for "Sensitivity:" in the Sensor Information Dialog Box.
-----------------------------


  
Hi all,



  Here is the procedure I use to calibrate my mini-Lehman type sensor.&=
nbsp; Does anyone have any comments?



Bob McClure



------------------------------

1. Set up limit stops on the pendulum so that it can be displaced over a kno=
wn and fixed number of millimeters at its radius of gyration.



2. Connect the sensor directly to the A/D, and log data as you move the pend=
ulum gently back-and forth a few times between the stops.  Record at a=20=
rate that gives a reasonable number of samples for the time taken to move be=
tween stops.  Do not move so fast that you exceed the voltage range of=20=
the A/D, otherwise you won't get valid data, and you might even blow out the=
 A/D.  Also, verify that the resistance of the sensor coil is low compa=
red to the input impedance of the A/D.



3. Make a WinQuake event file out of the data.



4. Use WinQuake to integrate the data.  You should see the actual displ=
acement versus time, measured in counts.  Measure the peak-to-peak disp=
lacement in counts.



5. Scale the count measurement to what you would have obtained for one centi=
meter of motion.  If you used 5mm of displacement, for example, you wou=
ld multiply your count estimate by two.



6. Multiply the scaled counts by the voltage gain setting of the amplifier y=
ou normally use.



7. Take the inverse of the number obtained in step 6.  This is the numb=
er you should enter for "Sensitivity:" in the Sensor Information Dialog Box.=


-----------------------------