I did a soak test, pending Kleinstein’s exact instructions.
Test Initiation
The intent of the test was to monitor the E-Load’s performance at 10v/1a=10w, over time.
Because I am unfamiliar with my oscilloscope, it took me about thirty minutes to find the waveforms and adjust the scope. The E-Load was working during this time. Meaning the E-Load and all the test equipment was fully warmed, when I took the first readings.
Initial Readings
Ambient temp was about 23.8*C.
Time: 2pm
PSU as DUT: set at 9.99Vdc @ 1.4A available. The extra 0.4A on the PSU was allowed to see if the E-Load would drift.
E-Load was set at 0.099945A x 10 (Shunt Factor). The E-Load does not have provision to limit the voltage, so the voltage was the full voltage available.
MOSFET Face Temp: 36.7*C
Shunt/Sink Resistor Touch Test: Tepid, not hot, or cold.
See PNG2 for waveforms.
Yellow: Probe1 was attached to a flywire soldered to the output of R6, which is tied directly to the input of the MOSFET.
Purple: Probe2 was attached to the input pin of the Shunt/Sink Resistor; R9
Both probe ground leads were tied to circuit ground/neutral.
![](https://www.eevblog.com/forum/projects/electronic-load-project-ltv171-irfp250-with-kicad-files/?action=dlattach;attach=904140)
One Hour Soak Readings
Ambient temp was about 23.8*C.
Time: 3pm
PSU as DUT: set at 9.99Vdc @ 1.4A available. The extra 0.4A on the PSU was allowed to see if the E-Load would drift.
E-Load drifted slightly to 0.099928A x 10 (Shunt Factor). The E-Load does not have provision to limit the voltage, so the voltage was the full voltage available.
MOSFET Face Temp: 37.0*C
Shunt/Sink Resistor Touch Test: Tepid, not hot, or cold; no discernible change.
See PNG3 for waveforms.
Yellow: Probe1 was attached to a flywire soldered to the output of R6, which is tied directly to the input of the MOSFET.
Purple: Probe2 was attached to the input pin of the Shunt/Sink Resistor; R9
Both probe ground leads were tied to circuit ground/neutral.
![](https://www.eevblog.com/forum/projects/electronic-load-project-ltv171-irfp250-with-kicad-files/?action=dlattach;attach=904136)
Conclusion
At 10v/1a = 10w, the E-Load exhibited minimal drift in the load sunk. 0.99945A – 0.99928A = 0.00017A. 0.00017A/0.99945A = 0.000017% Current Drift.
The MOSFET Face Temperature drifted from 36.7*C to 37.0*C, being a drift of only 37.0 – 36.7 = 0.3. 0.3/36.7 = 11.01%
The Shunt/Sink Resistor performed without labor/heat.
No errant waveforms were encountered.
The minimal current change is considered excellent for a DIY device. The temperature change is attributed to ambient influences and is considered not significant.
I performed the test under my best-guess as to what Kleinstein might instruct. If I did the test mostly correctly, then I am impressed with the results. Pushing the E-Load to its designs limits will be interesting.