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PXI-4130

Assume, I have a UUT that momentarily shuts off due to insufficient peak current from the PXI-4130.  My UUT is rated for ~1.7A, 12V.  The PXI-4130 is using the NI Auxiliary Power Source APS-4100 that provides the up to 20V, 2A on channel 1 of the PXI-4130.

 

Are there power ratings for peak current when using the PXI-4130 w/ Auxiliary power?  

If I take a AC/DC adapter rated at 12V, 2A the UUT successfully operates. 

 

 

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20V 2A with aux PS is a continuous power rating. Given this is a power supply, there is a control loop that limits the current and maintains the voltage, whereas in a regular AC/DC adapter there is no strict current limiting and in reality, your UUT might need more than 2A for a short burst and the adapter was forgiving.

 

One way to work around this is to add a significantly sized capacitor near the DUT so that any short bursts of current requirements are satisfied by the capacitor and not be the 4130.

Santhosh
Soliton Technologies

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Santhosh, thanks for the information.  I'll keep the capacitor idea in mind.

 

Btw, I went seeking for a way to program the PXI-4130 current limit mode but that's not an option.  Usually, programmable PS can be set to current limit (maintaining Voltage) instead the PXI-4130 cutting off current at its 2A limit.

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When in Source Voltage mode all NI DcPower instruments try to maintain the sourced voltage within the current limit. If the current limit is reached, the current is maintained while the voltage is reduced appropriately to maintain the current limit.

 

The reality could be as soon as it reached the 12V 2A limit, PS had to reduce the voltage to below 12V to not exceed the 2A limit due to increased UUT requirements but this reduced voltage may be affecting the UUT.

 

If you have an oscilloscope, you can probe the voltage rail and observe this voltage drop.

Santhosh
Soliton Technologies

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@santo_13 wrote:

When in Source Voltage mode all NI DcPower instruments try to maintain the sourced voltage within the current limit. If the current limit is reached, the current is maintained while the voltage is reduced appropriately to maintain the current limit.

 

The reality could be as soon as it reached the 12V 2A limit, PS had to reduce the voltage to below 12V to not exceed the 2A limit due to increased UUT requirements but this reduced voltage may be affecting the UUT.

 

If you have an oscilloscope, you can probe the voltage rail and observe this voltage drop.


Thanks for the response, can you point me to documentation explaining that NI PS products do jus that - "current is maintained while the voltage reduced".  

 

Prior to your response, I did just that, put a programmable load on the NI PXI-4130 w/ APS-4100 set the load current to 1.99A then 2.00A hit the enable button and the load Voltage dropped to 0!  When I used 1.98A (12V I believe) all was well, meaning power was maintained.

 

I"m quite sure the PXI-4130 is setup for Voltage Source aka Source Voltage.

 

Oh, forgot to mention, I was looking at the DCV using a O-scope and the voltage dropped off the screen, immediately, then the voltage returned to the DC setting, the load then read 0W (power).

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I over-turned every stone on the PXI-4130 properties and methods.  It doesn't support programmatically when the outputs are "latched", i.e. turned off.  Only way to enable the output is to setup a new session and set the output to enabled.  

 

I found a property that enables values 105% over the limits but the PXI-4130 doesn't support that and the values are too low for passing peaks anyhow.  

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Anyone,

Is there a way to set the PXIe-4130 to limit current ONLY and not shut-off power when 2A is reached, then it immediately reapplies the setup voltage.  

 

If you take any other programmable power supply, Keysight, Tektronics etc. , they provide a setting to limit current but not shut-down power.  Shutting down power ruins testing.

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I am pretty sure that once compliance current is reached, the voltage is regulated to limit the current in CV mode and the output does not turn off unless the load is a short circuit.

 

One more property you can try is this,

santo_13_0-1649619939445.png

 

One more experiment, use the E-Load in constant R mode at 5 ohms, operate the power supply, now, if the power supply is really behaving as you say, it should turn Off immediately, but if it is behaving as per my understanding, the voltage should drop to 10V while maintaining 2A.

 

Santhosh
Soliton Technologies

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The Output Cutoff property is not supported by the PXI-4130. An "x" in the list below means it is not supported by the PXI-4130.

 

I was able to solve my issue by putting the PXI-4130 in constant current mode.  A voltage level still needs to be set when this is done or the default voltage is 20V.  This essentially turns off the feature to kill the power when the 2A limit is reached.  I plotted I and V while in constant current mode, you can see the voltage vary, slightly, as the peak currrent (2A) is reached.  Anyhow again, in this mode the power is not killed.

 

Thanks for the suppport.

 

PXI4130_Output_Cutoff.PNG

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