Analog Input impedance, power and documentation PXIe-6363

[johngardner58]

Hi,

I have a clarification question.   Datasheet indicates the analog input impedance of > 10GΩ when the device is powered on and 820Ω when off.   My question is: "what does it mean for power on and power off"   Does it refer to the power applied to the card itself or some power state of the particular analog input?   I assume the former but want to be absolutely clear.  I have a PXI-4071 that I can switch around to various pins on the DUT using a PXI-2530b matrix.   One of the DUT pins I may fix an Analog Input to as a secondary way of measuring voltage.  This means that on occassion both the DMM and Analog Input will be connected to the same pin at the same time.   I don't want the Analog Input introducing errors to the DMM.

The reason I want an analog input as a secondary voltage measurement source is that the DUT pin connects to analog test pin that mux's to many other test points.   This way I can have the DMM at a different location and measure for example the voltage at the input of an opamp and the voltage at the output at roughly the same time.   But I will also want to switch the  DMM to the text_mux for precision measurements.   This avoids switch matrix complications.

[johnsold · Accepted solution]

Those input impedance specifications refer to the power state of the PXIe-6363. When the module has power applied, the inputs are high impedance. With no power applied to the module the lower impedance can occur.  Most likely the input multiplexer on the 6363 has some protection diodes which are reverse biased when powered. If the device has no power applied, then the diodes can conduct resulting in a very low input impedance.

As long as everything is in the same chassis I do not think you will have any problems with loading inputs.

Lynn

[johngardner58]

Thanks that what I was expecting!