# Digital Multimeters (DMMs) and Precision DC Sources

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## PXI 4110 parallel 2 isolated ouputs

Hello ,

I am going to use PXI 4110 to supply DUT. If DUT current is larger than 1A, is there any risk to parallel 2 isolated output to supply more current? Is there any notes I should take?

Thanks,

Leo

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## Re: PXI 4110 parallel 2 isolated ouputs

Hey Leo,

Do you already own the 4110 modules?  If not, take a look at the 4130, which has a 2A output on channel 1.  If you do already own the 4110 modules, go ahead and hook them up in parallel; since they're single quadrant modules (they can only source power), there's no risk that they'll sink into each other.  Even if the voltage is different, there's no risk, but obviously you'll want the voltage levels to be the same so that the voltage doesn't drop to the lower of the two supplies once you exceed 1A. To get the total current, just add the measured values from both modules.  I recommend keeping the leads between the two modules short.

Note that you can't tie multiple 4130 modules (or any SMU for that matter) in parallel because those modules can both source and sink current... still won't cause any damage to the modules, but they'll sink current into each other (specifically, the higher voltage module will sink current into the lower voltage module), resulting in inaccurate current measurements.

-John Sullivan
Problem Solver
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## Re: PXI 4110 parallel 2 isolated ouputs

Thanks John,

I only have one 4110 module, I am not going to tie 2 modules together but tie 2 chanel of the 4110. Is it OK?

Leo

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## Re: PXI 4110 parallel 2 isolated ouputs

Hey Leo,

On the 4110 you can tie channels 0 and 1 together, but unfortunately you can't tie channels 1 and 2 because they share a common floating ground and channel 2 is negative only.  Theoretically, you could tie channels 0 and 2 together, which would be useful if you then needed a more positive voltage than that combined rail.  Note that channel 0 is only 0-6V, so you'll need to limit the overall output voltage to that range.

-John Sullivan
Problem Solver
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Message 5 of 8
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## Re: PXI 4110 parallel 2 isolated ouputs

Hi TH64,

The conversation above is referring to connecting modules in parallel to increase the overall current output.  John was correct in saying that it isn't possible to connect channel 1 and 2 of a single 4110 module in parallel to achieve a higher current output.  If you look at section 2 of the white paper you linked, you'll see that channel 1 and 2 are never connected in parallel.

However, it is possible to connect channels 1 and 2 together in series to increase the voltage output of the module as Figure 1 B in your link shows.

Let me know if you'd like any further clarification.

Regards,

Jared R.
Precision DC Product Support Engineer
National Instruments
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## Re: PXI 4110 parallel 2 isolated ouputs

My mistake, didn't read the post thoroughly.

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## Re: PXI 4110 parallel 2 isolated ouputs

Hey there,

Which part was unclear.  I'd like to make sure our white paper isn't confusing users.  Let me know what was unclear and I can clarify.

-John Sullivan
Problem Solver
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