NI USB 6008 Analog Inputs

[prasan89]

Hello Everyone,

Currently I am using NI6008 devices for some projects & I am having some issues while taking Analog inputs. When I look into the schematics of the Analog inputs of the NI 6008 datasheet, I can see a series resistor & a resistor divider just before the MUX. But when i check the actual hardware, I can see a Varistor in between each channel & GND which is not shown in the datasheet.
Now I know the article description of that Varistor.

[PahlM]

Hello Prasan89,

What exact issues are you seeing when taking analog inputs?

Regards,

Michael Pahl

 Applications Engineer

 National Instruments

 www.ni.com/support 

[prasan89]

Hello Michael,

When I measure voltages upto somewhere 9V. Sometimes it consumes some mA current. likewise sometimes i got lower voltage values than actual value.

Can you let me know the value of that Varistor. so that I can measure, if it is within the limits or not.

Thanks,

Prasanna

[PahlM]

Prasanna, 

How much current is the 6008 consuming?

Also, how far off is the voltage measurement?

Regards,

Michael Pahl

 Applications Engineer

 National Instruments

 www.ni.com/support 

[prasan89]

Hello Michael,

Current around 2mA.

Is it possible you to tell me the exact value of the varistor which is added to the measurement line.

Thanks,

Prasanna

[PahlM]

Prasanna,

No, we do not disclose that information. If you tell us more about your set up and what you are seeing then we can troubleshoot the issue together, but we do not disclose that.

Regards,

Michael Pahl

[prasan89]

Hello Michael,

Can you support me to find a compatible protection device which can be fix in between NI6008 & analog measuring points.

It should have a capability of stop unnecessary surge pluses such as Back EMF. Because my application also having 200mH inductor on one measurement path. likewise it should not disturb to my measurement values.

[PahlM]

Hello Prasan,

I think your best help would be to contact our sales department. They work at the system level of projects and they can help you generate a quote for a product. 

They can also bring technical support in if they need a technical question answered that they do not know immediately.

Their number is : (877) 387-0015

PahlM