I have a DC electronic system that takes approx. three minutes to boot up, and I have to decide what gauge wire to make power cables. During boot up, this system powers on several different sub-systems, cooling fans, LCD display, processor etc... each producing their own current spike. With what tool can I measure max inrush current (amps rounded to .5) over approx 3 minutes?

  • 4
    \$\begingroup\$ A datalogger with a current sensor. \$\endgroup\$
    – Solar Mike
    Commented Sep 27, 2023 at 18:16
  • \$\begingroup\$ Thanks Mike, but would a datalogger have a high enough sample rate to catch a spike at only 100s/s? \$\endgroup\$
    – mikey B
    Commented Sep 27, 2023 at 18:24
  • \$\begingroup\$ @All - Please don't answer a question in comments - that is not an allowed use of comments. See here & here. || Even short answers are answers and should be posted as such. As explained here regarding answers: "Brevity is acceptable, but fuller explanations are better." so a clear single sentence answer is acceptable, if that's all it needs. || There are many problems with answering in comments, too many to list here and some that people probably didn't realise, but they can harm the site. Thanks. \$\endgroup\$
    – SamGibson
    Commented Sep 27, 2023 at 18:25
  • \$\begingroup\$ Why do you think you're going to have current spikes when the various parts of the system power on? And what controls the power turn on of those pieces? Well designed power supplies, for example, ramp up their output voltages over tens of milliseconds, or longer. \$\endgroup\$
    – SteveSh
    Commented Sep 27, 2023 at 20:37

2 Answers 2


A Tektronix scope with a current probe. Most of the newer tek scopes can measure in the minutes range. If you needed to catch a spike you could trigger. Othwise set it into roll mode and integrate over 3 minutes. You do need to be able to do a calibration on the scope and back convert voltage (on the scope) back to current.

  • \$\begingroup\$ Is that "tek" or "Tek"? \$\endgroup\$
    – Transistor
    Commented Sep 27, 2023 at 20:44
  • \$\begingroup\$ Tektronix... I'll update\ \$\endgroup\$
    – Voltage Spike
    Commented Sep 27, 2023 at 20:45

Ammeter with a peak hold function. But look carefully at your assumption that the max current draw will be at bootup. Are the cooling fans temperature controlled? Is the processor at maximum load?


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