mcc172 MCC 172 measurement of acceleration and velosity

[Mussa]

MCC 172 measures the voltage of the IEPE sensor, right?
How to convert this data into acceleration and velocity?

[Jeffrey]

Hello @Mussa

8 minutes ago, Mussa said:

MCC 172 measures the voltage of the IEPE sensor, right?

As it states on the webpage, "The MCC 172 is a two channel DAQ HAT for making sound and vibration measurements from IEPE sensors like accelerometers and microphones," so yes.

 

9 minutes ago, Mussa said:

How to convert this data into acceleration and velocity?

The MCC 172 measures voltages over time.  Assuming the voltage is some sort of distance or speed measurement...

I recommend you look at the example finite_scan for the MCC 172.  It will demonstrate how to set up the MCC 172 for hardware paced data collection.  In this example, note the sample rate is 10,240 Hz, meaning a new sample will be acquired every 1/10240 seconds or 97.6 microseconds (or uS).  Knowing that, you can calculate acceleration from rate x to rate y by finding the data indexes for X and Y voltages in the collected data, then count the number of samples collected between X and Y.  or stated another way, find the data index for Y and subtract the data index for X.  This will tell you how many samples it took to get from voltage X to voltage Y.  Multiply the resulting difference by 97.6 uS, and you will have how long it took to get from voltage X to voltage Y.

The same is true for velocity.  In this scenario, each voltage measured will equate to a certain distance traveled as stated in the data sheet of your IEPE sensor's spec. You would then add the successive samples for a particular number of samples to provide you with a distance.  The time is the number of samples * 97.6 uS.

Regards,

Jeffrey

[Mussa]

Hi @Jeffrey

I carefully read MCC DAQ HAT LIBRARY (https://mccdaq.github.io/daqhats/c.html#c.mcc172_a_in_sensitivity_write).

It says:

"Write the MCC 172 analog input sensitivity scaling factor for a single channel.

This applies a scaling factor to the analog input data so it returns values that are meaningful for the connected sensor.

The sensitivity is specified in mV / mechanical unit. The default value when opening the library is 1000, resulting in no scaling of the input voltage. Changing this value will not change the values reported by mcc172_info() since it is simply sensor scaling applied to the data before returning it.

Examples:

- A seismic sensor with a sensitivity of 10 V/g. Set the sensitivity to 10,000 and the returned data will be in units of g.

- A vibration sensor with a sensitivity of 100 mV/g. Set the sensitivity to 100 and the returned data will be in units of g."

So I think that when we are using the sensitivity parameter, the polling program shows the value in "g".

Is it correct?

 

Edited December 7, 2022 by Mussa

[1zhangyo]

On 12/7/2022 at 4:29 PM, Mussa said:

Hi @Jeffrey

I carefully read MCC DAQ HAT LIBRARY (https://mccdaq.github.io/daqhats/c.html#c.mcc172_a_in_sensitivity_write).

It says:

"Write the MCC 172 analog input sensitivity scaling factor for a single channel.

This applies a scaling factor to the analog input data so it returns values that are meaningful for the connected sensor.

The sensitivity is specified in mV / mechanical unit. The default value when opening the library is 1000, resulting in no scaling of the input voltage. Changing this value will not change the values reported by mcc172_info() since it is simply sensor scaling applied to the data before returning it.

Examples:

- A seismic sensor with a sensitivity of 10 V/g. Set the sensitivity to 10,000 and the returned data will be in units of g.

- A vibration sensor with a sensitivity of 100 mV/g. Set the sensitivity to 100 and the returned data will be in units of g."

So I think that when we are using the sensitivity parameter, the polling program shows the value in "g".

Is it correct?

 

Why nobody answers you? I'm as confused as you are.

[Joshua_W]

As far as I am aware from my testing all this setting does is apply some multiplicative factor to the data collected. It does not preform any amplification afaik.

[JRys]

That is correct; the sensitivity setting scales the voltage to g's. For velocity, you need to integrate the data. Usually, the FFT data gets integrated once for velocity and twice for displacement. Unfortunately, the MCC 172 API has no signal processing functions. 

Best regards,

John