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measuring a 20A power diode

Model 2651A
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kellekellner
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Joined: March 10th, 2015, 8:19 am
Country: Germany

measuring a 20A power diode

Post by kellekellner » March 10th, 2015, 8:30 am

Hello,
we want to measure a 20 Amps power diode. But we don't get a nice result. The result seems to be distorted.
I'm thinking there is a fault in our plan. We sweep the voltage from 0V to 1V linear and we are reading the current. But the current only stays at 15 Amps at 1V.
Did we get to the limit of the 2651A SMU? Or should we sweep the current from 0 Amps to 20 Amps and read the voltage.

Thank you for your help and excuse my bad English.

Andreas Kellner

brian.d.smith
Keithley Applications
Keithley Applications
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Country: United States

Re: measuring a 20A power diode

Post by brian.d.smith » March 11th, 2015, 4:12 am

My experience is that you should force current and measure voltage. Depending on the inductance of the device and your setup, you may have to integrate over a longer time to find the place where ringing has subsided.

Are you using remote sense? You should definitely use remote sense.

Are you using TSP Express? If so please post a snapshot of the setting. It would be good to also post a snapshot of your device and cabling.

kellekellner
Posts: 2
Joined: March 10th, 2015, 8:19 am
Country: Germany

Re: measuring a 20A power diode

Post by kellekellner » March 12th, 2015, 8:07 am

Thanks for the fast answer.
what did you mean with force the current? Actually i tried to sweep the current from 0 A to 20A. But the voltage curve isn't right. At 15 Amps the voltmeter measure strange thinks.
So i tried a simple resistor and the result is that the curve is linear until about 15 Amps but then the voltage dropped for 1 Amp and then it rises a little bit. But not linear. Is there a fault in the SMU or our cabling. At the moment I can't send you a - of our cabling. I think the cables are about 50 cm each and at the end we put the source high with the sense high at a clamp.

I hope you can help me.

Thank's a lot

Andrea C
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Re: measuring a 20A power diode

Post by Andrea C » March 13th, 2015, 2:53 am

When sweeping current, what is the setting for the voltage compliance limit?

Are you operating in a pulse mode or continuous?

brian.d.smith
Keithley Applications
Keithley Applications
Posts: 402
Joined: June 10th, 2013, 6:00 am
Country: United States

Re: measuring a 20A power diode

Post by brian.d.smith » March 13th, 2015, 6:08 am

kellekellner wrote:Thanks for the fast answer.
what did you mean with force the current? Actually i tried to sweep the current from 0 A to 20A. But the voltage curve isn't right. At 15 Amps the voltmeter measure strange thinks.
So i tried a simple resistor and the result is that the curve is linear until about 15 Amps but then the voltage dropped for 1 Amp and then it rises a little bit. But not linear. Is there a fault in the SMU or our cabling. At the moment I can't send you a - of our cabling. I think the cables are about 50 cm each and at the end we put the source high with the sense high at a clamp.

I hope you can help me.

Thank's a lot
Your cables and connections are very important. SENSE HI and LO connections should not be stacked with the output/force connections. The SENSE HI and LO connections should be as close to the device as physically possible while the FORCE HI and LO should be a little further away from the device than the SENSE connections.

Also, are you using remote sense? Are you sweeping DC or pulsed?

If you are using DC, there will most likely be self-heating of the device at higher currents and the resistance will change with temperature. Pulsed mode reduces self-heating.

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