Multifunction DAQ

cancel
Showing results for 
Search instead for 
Did you mean: 

Using Accelerometer on NI 9220

Hi all,

 

I am having trouble connecting my accelerometer to NI 9220. The output does not make sense at all.

 

Please find attached the photos (file name Figures.pdf of what I use to connect the accelerometer (Figure 1). Please ignore the wires as they belong to another device.

Basically I use the blue and grey connectors to power the accelerometer, and the NI 9220 to obtain the output. As seen in Figure 2, the accelerometer has 4 wires. Figure 3 shows how the wires are supposed to be connected. By following Figure 3, I connected the accelerometer's wires as such:

1. Red and black to the positive and negative power source (i.e. the blue and grey boxes) respectively.
2. Green to one of the AI+ slot on the NI 9220.
3. White to one of the AI- slot on the NI 9220.

This connection gives me some results that do no make sense at all, and with significant amount of noise. May I know what have I done wrong in the connection?

 

The specification of the accelerometer has also been attached.

 

Thank you very much. Any help is highly appreciated 😃

0 Kudos
Message 1 of 8
(4,236 Views)

What kind of signal are you reading in? Is it just noisy? Could you please attach screenshots?

0 Kudos
Message 2 of 8
(4,219 Views)

Thank you for the reply. 😃

 

Please find attached the output graph from the accelerometer. I haven't done the sacling yet so y-axis is in terms of Voltage. 

 

I didn't move the accelerometer at all when logging the data. As you can see, the output voltage is stucked at about 10.5V, and can fluctuate down to 8.5V. I don't understand why it is behaving like this. I think there could be something wrong with my connections.

0 Kudos
Message 3 of 8
(4,208 Views)

Have you tried reading a known signal from a power supply of something like that?

0 Kudos
Message 4 of 8
(4,189 Views)

Your source seems to float. ... and there is no bias path ...

 

From pos and neg exitation connect a 10k ohm resistor to the COM input , so two resistors total ;). 

OR connect the GRN sensor wire to pos input and a 1M Ohm from the pos input to COM

 

and you can try to connect the shield to COM too.

 

Greetings from Germany
Henrik

LV since v3.1

“ground” is a convenient fantasy

'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'


0 Kudos
Message 5 of 8
(4,141 Views)

The max output of the sensor is +-400mV  and your fixed input range is +-10V .

you loose about 4-5  most significant digits. depending of the task you want to solve I recommend a instrmentation preamplifier (INA) with a gain of 10 to 20.

 

And you should investigate your supply voltage. This type sensor is only specified for a 10V supply and the output is ratiometric to the powersupply.

If you add an amplifier it's woth to monitor the bridge supply.

Greetings from Germany
Henrik

LV since v3.1

“ground” is a convenient fantasy

'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'


0 Kudos
Message 6 of 8
(4,131 Views)
Thank you for the reply! After connecting the negative output (AI-) to COM, the noise seems to be lowered. However, two issues remain: 1. The measurement I got (before any scaling) is between 4.6-4.7V if I use an input voltage of 9V (I don't have 10V power supply at the moment). This is very different from the output I expected according to the datasheet, which is 400mV maximum output as you mentioned. 2. I changed the output to real time V-t graph. However, it does not have any response even when I shake the accelerometer. Again, thank you in advance!
0 Kudos
Message 7 of 8
(4,111 Views)

Please provide a schematic of the wirering ....  Seems not one of the two I proposed 😉

 

You have a differential input and COM. IF you have a floating source use the two resistor method. OR   If you look at the sensor datasheet you see two 500Ohm resistors to complete a full bridge, they are connected to the GRN (pos) output, that why I recomment an additional bias path resistor from the GRN (pos signal) to COM with a value of 10k to 1M ... 

 

If you (ab)use the 10V supply for other sensors/things add them in the schematic including ground impedances.

 

 

 

If you shake the sensor  I expect about 600µV signal amplitude....  easely buried in the noise, that why I recommend a preamplifier ....  look for industrial signal conditioners with 10V bridge supply +-10V output and a gain of ~20.  (DEWETRON and others makes Labversions)

 

 

Greetings from Germany
Henrik

LV since v3.1

“ground” is a convenient fantasy

'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'


0 Kudos
Message 8 of 8
(4,095 Views)