AC/DC coupling in LabVIEW

[nagesh15]

Hello all,

              Need help. I have used  AC coupling for voltage acquisition in LabVIEW for NI 9215 earlier but now I am unable to use it. I have to remove AC coupling. When I select AC coupling. A message pop-up that shows DC coupling is possible. Where is the wrong. 

LabVIEW 15

DAQmx 15.5.1

[GerdW · Accepted solution]

Hi nagesh,

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@nagesh15 wrote:

Need help. I have used  AC coupling for voltage acquisition in LabVIEW for NI 9215 earlier but now I am unable to use it. I have to remove AC coupling. When I select AC coupling. A message pop-up that shows DC coupling is possible. Where is the wrong. 

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What's wrong here?

According to the datasheet the NI9215 does not offer any "AC coupling" (atleast I didn't find it mentioned in there).

So what do you expect here?

[nagesh15]

But I have used AC coupling in 9215. 

When I am taking data using no AC/DC, I am getting offset in signal. Is that always give offset with AC/DC coupling

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@GerdW wrote:

Hi nagesh,

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@nagesh15 wrote:

Need help. I have used  AC coupling for voltage acquisition in LabVIEW for NI 9215 earlier but now I am unable to use it. I have to remove AC coupling. When I select AC coupling. A message pop-up that shows DC coupling is possible. Where is the wrong. 

---

What's wrong here?

According to the datasheet the NI9215 does not offer any "AC coupling" (atleast I didn't find it mentioned in there).

So what do you expect here?

---

---

@GerdW wrote:

Hi nagesh,

---

@nagesh15 wrote:

Need help. I have used  AC coupling for voltage acquisition in LabVIEW for NI 9215 earlier but now I am unable to use it. I have to remove AC coupling. When I select AC coupling. A message pop-up that shows DC coupling is possible. Where is the wrong. 

---

What's wrong here?

According to the datasheet the NI9215 does not offer any "AC coupling" (atleast I didn't find it mentioned in there).

So what do you expect here?

---

?

[GerdW · Accepted solution]

Hi nagesh,

---

@nagesh15 wrote:

But I have used AC coupling in 9215. 

When I am taking data using no AC/DC, I am getting offset in signal. Is that always give offset with AC/DC coupling

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The datasheet does NOT mention any "AC coupling" for the NI9215. DAQmx also says "no AC coupling available".

But you insist on using AC coupling? I don't see any option for that…

[RTSLVU]

Put a capacitor in series with the input to block any DC offset.

BTW: That's exactly what "AC Coupling" does in an oscilloscope.

[GerdW · Accepted solution]

Hi nagesh,

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@RTSLVU wrote:

Put a capacitor in series with the input to block any DC offset.

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I guess you already know how AC coupling is implemented.

When NI hardware supports such a feature then the datasheet will also mention the feature explicitely - like NI does for the NI9232 module…

[nagesh15]

Thankyou for reply. 

1. Why it used AC coupling in NI 9215?

2. Does 9215 gives offset during aquisition with no coupling selection? I am getting offset but when I selected AC coupling I am getting no offset.

 Please , explain.

[GerdW]

HI nagesh,

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@nagesh15 wrote:

1. Why it used AC coupling in NI 9215?

2. Does 9215 gives offset during aquisition with no coupling selection? I am getting offset but when I selected AC coupling I am getting no offset.

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1. We don't know, it shouldn't offer AC coupling for this hardware…
2. What "offset" are you talking about? Why do you get "no offset" with AC coupling enabled when your DAQmx/VI says it does not support AC coupling?

All the time you missed to attach your VI and some measurement results when we discuss about your hardware and the options it does not support…

[billko]

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@nagesh15 wrote:

Thankyou for reply. 

1. Why it used AC coupling in NI 9215?

2. Does 9215 gives offset during aquisition with no coupling selection? I am getting offset but when I selected AC coupling I am getting no offset.

 Please , explain.

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#2 - Basic electronics.  Serious question: are you sure you're qualified to be operating this equipment?

[nagesh15]

Blue curve is with No AC/DC coupling and red curve is for AC Coupling. These signals I got using same NI 9215 and same time back to back.