NI 5761 input voltage range

[hht3lasers]

Hello,

What is the simplest way to change the input range for the NI 5761?  I've tried reading the CLIP reference under the help and looked at the Texas Instruments data sheet for the ADC, but it's not clear to me how to piece everything together.

Thanks.

[A_Donfigulation_Error_Has]

Hi hht3lasers,

The NI 5761 does not have an adjustable input range. From the specifications on page 13 http://www.ni.com/pdf/manuals/375509a.pdf , you can see that the voltage range is only specified for a range of 2.07Vpk-pk in AC coupled mode and on page 16 as 1.23 Vpk-pk for DC-coupled mode.  You can change the device between AC-coupled or DC-coupled. Check out the NI 5761 folder in the LabVIEW example finder, as this code is implemented in one of the shipping examples. From the Example Finder, navigate to Hardware Input and Output >> FlexRIO >> IO Modules >> NI 5761 >> NI 5761 Getting Started.lvproj.

Regards,

Jason L.

[Dave.T]

Hello hht3lasers! 

What voltage range do you need?  

Register 55 in the ADC is the one responsbile for adjusting the gain.  We haven't don any testing on changing that gain and can't guarauntee the performance of the 5761 when you change it, but you do have the power!  

You would have to write a vi that does a SPI write to that register.  While it's not exactly the same, you can look at the 5752 configure ADC example and model the code after that.  

Again, we haven't tested this, and therefor it's not supported.  

[hht3lasers]

Thank you!  I will give it a shot and see how it goes...

[mvdhoef]

Did you have any luck with this?  I am attempting to do the same configuration.  I need to set the ADC gain to 6db but the SPI communication does not seem to be working...

[hht3lasers]

Unfortunately, I have not had a chance to try it out. 

[shef1]

I am also trying to change the input voltage range of NI 5761 (dc coupled version). The current voltage range is 1.23 V peak to peak. I want to reduce the range to 0.5 V peak to peak. Has anyone succeeded to change the input voltage range of NI 5761? Please help me.

[DollaBrillz]

Hi,

Are you using the method suggested by Dave T (a few posts back) to adjust the Vpk-pk for DC coupled mode?. To reiterate what was said here, this is something that is possible but is not tested, so you cannot guarantee the performance of the card. What are the requirements that you are working with, and is changing this your only option?

[mvdhoef]

Yes.  I have been able to successfully change the ADC gains on the 5761 using SPI communications.  I set the ADC gain to 6db (Max gain according to ADC datasheet, there are a couple other gain options) to cut the input voltage range in half.  This gain must be set every time the card is initialized.  It is possible and it does work well.

[shef1]

Hi Mattias,

Thanks a lot for you reply. Can you please share the VI you have used to change the gain of NI 5761, if it possible for you?