Not sure what thread you'd be referring to since that was ages ago - but usually people round here measure current with a shunt and a voltmeter. Something like a big wirewound 1ohm resistor makes it easy, so 1A=1V
He posted this , but i want to know how he got this , i know that its an oscilloscope but its a current clamp plugged in or else ?Startup spikes are downright terrifying. And it would probably be worse (to the point of blowing up my test load perhaps??) If the voltage set point was higher. As always, note the time base in each image because they change to show detail.
At 1.8A switched before the driver:
Is that what you where talking about :Not sure what thread you'd be referring to since that was ages ago - but usually people round here measure current with a shunt and a voltmeter. Something like a big wirewound 1ohm resistor makes it easy, so 1A=1V
If i have a 1ohm +-5% or 10% i will still be able to see the current spike (on the dso) if there is one , and i can check the current precisely via my multimeter?I have some 1% 1 ohm resistors in power ratings from 5 watts up to 100 watts. It is important to get the most accurate resistors you can to measure current using a shunt resistor. It is easier to incorporate either a 1 ohm or a 0.1 ohm resistor in a dummy load to measure the current as you don't have to interrupt your circuit to put an ammeter in series with it. Also, you needn't worry about blowing a fuse in your ammeter if you select the lower range than the current passing through your circuit.
I have found a 3w 0.1ohm 1% resistor .Yes, you should be able to see noise on your line if it exists, but you won't have an accurate measure of your current. In order to get that you need large, short connections between components in your dummy load and the most accurate resistors you can find.
Close, but a differential probe isn't necessary if your power supply is floating. Yours almost certainly will be, but you've surprised me several times before here, so we shall wait and see what ungodly setup emerges from this.
Not only will the resistance and readings wander all over town, it'll explode or begin smoking once you pass higher current though it. I promise.Resistor way (used a potentiometer set to 1ohm)
Not if you can measure and apply a calibration constant. The temperature coefficient is a far more substantial specification when it comes to accuracy. 0.001% resistor is useless as a shunt if it has a tempco of 10,000ppm/CIt is important to get the most accurate resistors you can to measure current using a shunt resistor.
...What? Please elaborate, because I suspect KCL is about to prove you wrong unless I'm misreading something or unless you retract something.In order to get [accuracy] you need large, short connections between components in your dummy load
It's not only for long conductive paths, it's not just above 4 amperes, and it's not just resistance and inductance either. ALL leads have ALL parasitics (in varying quantities) at ALL currents. It's a law of physics. How exactly are you insisting these affect the accuracy of the current reading at the shunt?for currents exceeding 4 amps where small, long conduction paths can add resistance and inductance to your circuit.
The issue with the equipment that you've defended here is that it "might" (read that as "will") miss information that you need to see. I get that you're only looking for a rough picture of what the supply is doing - but your DSO138 may not even give you that.Hey , i just want to check the input current for a brief moment , i dont need a ultra precise measurement. Just on/off for 2 s.