I used the shaker(1g RMS, Velocity (RMS) 9.8mm/s @159.2Hz) to measure the sensitivity of CMSS2200 and CMSS2100 sensors and the measurement details are below.

         

 

 

 Microlog1(rms)

 MicroLog2

SI No

Model

Bias

1g shaker

Sensitivity

1 g shaker

Sensitivity

S94443

CMSS2100

12.84V

0.984

9.84

0.985

9.85

S43814

CMSS2200

12.49V

1.24

12.4

1.27

12.7

S43811

CMSS2200

12.76V

1.23

12.3

1.19

11.9

S75804

CMSS2200

12.48V

1.24

12.4

SKF Sensor

S44744

CMSS2100

12.75V

0.968

9.68

         

Currently, we are using CMSS2200(S43814) sensor for the data collection at the customer site.

 

Based on the measurement table we have a feeling of uncertainty in our CMSS2200 sensor.

 

  • Both (2100 and 2200) sensor sensitivity is 100mv/g. But Measurement readings were not the same when using the shaker
  • CMSS2100 sensor readings were the same as other sensors readings  (Quick collect sensor, CMAS 100-SL Extension kit sensor).
  • Enveloped Acceleration(E2 filter) peak frequency detected  318Hz. please explain that reason.
  • The customer has compared our readings with other instruments. The customer readings are not the same with our CMSS2200 sensor readings .how do explain do them?.

         

 

Original Post
Walt Strong posted:

It looks like (without checking specs.) the accelerometers have a nominal 10 mv/g sensitivity and not 100 mv/g. 

Walt

Walt, certainly the 2100 is 100 mV/g.  More importantly I believe the OP is concerned why all thing being equal, the 2100 reads about 1 g and the 2200 reads about 1.25 g’s.

I read the OP table quickly, so I guess what is labeled as "Sensitivity" is Volts output; correct John? A while ago I rented the very nice calibrator from the Modal Shop. I found that not only the permanent accelerometers on the STG gearbox did not meet the Sensitivity specification, but new ones from Allen Bradley did not either!

Walt

First of all let me mention that I take note of the OP's question reading "Enveloped Acceleration(E2 filter) peak frequency detected  318Hz. please explain that reason."  The OP also states his shaker frequency is 159.2Hz so the 318 Hz is essentialy 2X of the shaker frequency.  We can make at least one supposition; that something non-linear is going on causing some non-sinusoidal motion and hence a 2X of supply frequency.  It would be nice to know the details of the shaker being employed for the testing and some pictures of the setup.

There is a bit of "science" to the use of a shaker for calibration.  Let's take the 9100D from Modal Shop as an example.  If you drill down the specifications you will find an entry for "payload" and an entry of 800 grams.  That means that above 800 grams on the table, and the mechanical motion may tend to be non-sinusoidal.

Now the OP has mentioned the CMSS2100 and CMSS2200.  The CMSS2100 weighs 90 grams and the CMSS2200 weigh 130 grams.  So the CMSS2200 weighs more, and in addition has a side mount for the cabling vs. top mount on the CMSS2100.  130 grams should be OK with most shakers, but I have seen some fixtures made from a piece of 1 inch x 1 inch keystock, 6 or 8 inches long to accommodate both transducers in a single test, what is called a reciprocity test.  If something like that is being done, then the total "payload" may exceed the rating of the shaker.  I have often seen a single transducer mounted with its intended magnet; again we might be pushing the "payload" limit of a shaker. 

I mentioned top mount vs. side mount for the cabling.  The cabling should not be restrained in any way; mor or less allowed to float freely. 

Any time I have been involved in using a shaker, I preferred to look at the input signal and output motion on suitable instrumentation to insure I had sinusoidal signals.  In the early days that might have meant an oscilloscope.  These days a device with a 2-channel capability would likely work.

One other thing is the mounting torque, for both units it is 2.9 Nm (24 in lbs).  This should be verified.

As a point of interest, the specs on the input (1g RMS, Velocity (RMS) 9.8mm/s @159.2Hz) should only result in about 1 mil pp shaker table movement. 

 

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