need experts advise for Reading accelerometer specifications

[joshua.svn]

dear sir,

Reading accelerometer specifications
Wilcoxon Research accelerometer specification
Dynamic specifications
Sensitivity
This specification shows the “nominal” sensitivity. This is the voltage output per engineering unit; for example, 100 Milli-Volts per g (100 mV/g) will yield an AC voltage output of 100 milli-Volts per g of acceleration. The AC voltage will alternate at frequencies corresponding to the vibrational frequencies. The amplitude of the AC signal will correspond to the amplitude of the vibration measured. All frequencies will be present simultaneously. This is what creates a vibrational signal spectrum.

Above explanation for ctc transducer .

please tell me what is equivalent milli volts out for the charge output piezoelectric transducer

(vibration ) mentioned as Charge Sensitivity pC/m/s2 .


it is written on the transducer. pC/m/s2 = how many ac milli volts.


svn.

 

[JonSea]

In order to use a charge mode accelerometer, you need an amplifier or charge converter, and special low noise cable (read that as pricey) between them. Those connections are critical because a charge mode accelerometer has a high impedance output. Even the oil from your fingertip will degrade the connection if you touch the center pin of the connector.

A charge converter has its own sensitivity specification... A common one is 10 mV/pC.

An accelerometer with integral electronics is definitely the way to go and much more reliable unless there are temperature extremes or other reasons that require use of a charge mode accel.

 

[joshua.svn]

sir ,

Thanks for the explanation. u r near my requirement. i am calibrating a vibration measuring instrument. which is have a transducer written pC/m/s2 . so i dint have a shaker table .

my idea is to give equivalent sinusoidal rms ac voltage with function generator .

so kindly give me the details of conversion deta like pC/m/s2 to milli volt .

joshua.svn

 

[JonSea]

You can't run an AC voltage signal directly into an input expecting a charge mode accel.

You can use a series capacitor to convert the voltage source into a charge so that it looks like an accelerometer. Sorry, it's been too long since I've done this so I've forgotten the details. Best bet is to look at the ap notes from Endevco.

 

[JonSea]

Since it appears you can't look up the Endevco application notes yourself, here is a link to the relevant information. Read the section on charge mode stimulation.

Endevco Ap Note 211

 

[JonSea]

As I recall, a 1000 pF series cap makes the mV level = to the pC level (I.e., 10 mV would be a signal proportional to 10 pC) but check the math - after 20+ years since having done this, I could be wrong!.

At any rate, the capacitor Ned's to be a high quality precision cap. The accuracy of this method is only as good as the value of the cap is known. A typical ±20% cap makes for a lot of error.

 

[stan713]

It looks like your initial question was answered but I agree that accelerometer datasheets (especially piezoelectric ones) can be difficult to understand. I recently published a blog post that can be used as a reference for understanding some common accelerometer specifications: https://blog.mide.com/accelerometer-specifications-decoding-a-datasheet

Hope this helps!

 

[jpanhalt]

If you are going to self-promote, it would be nice is you included other accelerometer types.

John

 

[stan713]

John,

Great point on the other accelerometer types! There are three main types: capacitive, piezoelectric (like the Endevco one this thread started on), and piezoresistive. Here's a link to a comparison between the three types: http://blog.mide.com/accelerometer-selection

Folks in this forum are probably interested in embedded options. Most accelerometers you'll find on DigiKey or Mouser will be capacitive; but look to Measurement Specialties for some embedded piezoresistive and piezoelectric accelerometers. I have had good experience with the 832M1: http://www.meas-spec.com/product/vibration/832M1.aspx and we're now exploring their piezoresistive option, 3038: http://www.meas-spec.com/product/t_product.aspx?id=2706

Thanks,

Steve