EEVblog Electronics Community Forum

Products => Test Equipment => Topic started by: Mike Warren on September 04, 2013, 11:11:38 pm

Title: Electronic Load - Trap for new players
Post by: Mike Warren on September 04, 2013, 11:11:38 pm
This cost me a few minutes yesterday, wondering why the turn-on of my MOSFET at 1 amp was so odd.

First picture is when using the electronic load and the second is with a resistor.
Title: Re: Electronic Load - Trap for new players
Post by: kizzap on September 05, 2013, 01:14:48 am
Care to explain what was happening?

-kizzap
Title: Re: Electronic Load - Trap for new players
Post by: crisr on September 05, 2013, 01:57:12 am
What's channel 1 and what's channel 2? I assume the e-load was used in constant current mode, since you said that the test was @ 1A; have you tried it in constant resistance, since you are comparing it to a resistor? And what brand / model of e-load was it?
Title: Re: Electronic Load - Trap for new players
Post by: uoficowboy on September 05, 2013, 03:46:28 am
Quote from: crisr on September 05, 2013, 01:57:12 am
What's channel 1 and what's channel 2? I assume the e-load was used in constant current mode, since you said that the test was @ 1A; have you tried it in constant resistance, since you are comparing it to a resistor? And what brand / model of e-load was it?
We have a BK Precision 8500 at work and I can say that it acts really strangely in constant resistance mode. I think it might be a digital control loop, not an analog one. So you get funny looking behavior (similar, but not the same, as this) when in constant R mode. Constant I mode tends to work well though.
Title: Re: Electronic Load - Trap for new players
Post by: Mike Warren on September 05, 2013, 06:42:48 am
Quote from: crisr on September 05, 2013, 01:57:12 am
What's channel 1 and what's channel 2? I assume the e-load was used in constant current mode, since you said that the test was @ 1A; have you tried it in constant resistance, since you are comparing it to a resistor? And what brand / model of e-load was it?

The blue channel is not relevant. It's just a signal feeding a voltage booster for the MOSFET gate. I was looking at it to see if it had any bearing on the distorted turn-on of the MOSFET. It didn't.

The load is a REK RK8511. It does pretty much the same thing in CR mode. I'd expect all these common loads (Maynyuo, B&K) to behave the same since they seem t all be based on the same design.