05-25-2016 03:58 AM
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 😃
05-25-2016 04:20 PM - edited 05-25-2016 04:20 PM
What kind of signal are you reading in? Is it just noisy? Could you please attach screenshots?
05-25-2016 09:14 PM
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.
05-26-2016 12:37 PM
Have you tried reading a known signal from a power supply of something like that?
05-30-2016 03:26 PM - edited 05-30-2016 03:30 PM
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.
05-31-2016 06:13 AM
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.
05-31-2016 08:56 PM
06-01-2016 09:08 AM - edited 06-01-2016 09:13 AM
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)