9411 Digital Input Issue

[jwright30]

I have an issue with a 9411 digital input module. With nothing connected to it I am seeing 1.5V between the digital input and ground. It is causing me to get erratic readings with an encoder. Has anybody else experienced this before?

Thanks,

-Jonathan

[JÞB]

---

@jwright30 wrote:

I have an issue with a 9411 digital input module. With nothing connected to it I am seeing 1.5V between the digital input and ground. It is causing me to get erratic readings with an encoder. Has anybody else experienced this before?

Thanks,

-Jonathan

---

How are you measuring the @1.5V if nothing is connected to it?  Something is obviously connected or there could be no measurement!  

[jwright30]

Flying leads

[GerdW]

Hi JWright,

---

@jwright30 wrote:

Flying leads

---

Why do you measure voltage on flying leads connected to a digital input?

The more interesting questions:

• What does the DI module tell you about the state of that DI channel?
• How much current does the DI deliver on those "flying leads"?
• Why do you care about unused DI channels?
• What do you want to coneect to that DI channel?
• Which of the possible connection types do you intend to use?

[jwright30]

I'm measuring the voltage because the digital input signals are showing as on with nothing connected. I was having issues with a single ended encoder and during investigating it I noticed every channel was showing as on, which led me to measure the voltage with a multimeter. I don't know the current it delivers. I'm about to replace the module and see if the problem is still there.

[jwright30 · Accepted solution]

found the answer to the 1.5V reading: https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z0000015CiOSAU&l=en-US

[jwright30]

Fixed the issue with a pull down resistor from the digital input to ground. Thanks for the helpful questions