Ok folks. I did some investigating. After hooking everything up, I checked the resistance at 3 amps and at 0.
And now I'm a bit confused. Why? Because what I found seems backwards to me. When putting out 3 amps, I got a reading of 1.67k ohms. And at 0 amps, 16 ohms. Less resistance, less current???
Ummmm....Why?
You can't measure resistance in an active circuit. It simply will not work. You can calculate it. Measuring resistance with a meter involves putting a small voltage on the probes and measuring the current flow. In a powered up circuit the currents in that circuit swamp any expected effect from the meter.
You can, and should measure voltage or current in a powered circuit.
Grumpy_Mike:
You can't measure resistance in an active circuit. It simply will not work. You can calculate it. Measuring resistance with a meter involves putting a small voltage on the probes and measuring the current flow. In a powered up circuit the currents in that circuit swamp any expected effect from the meter.You can, and should measure voltage or current in a powered circuit.
The circuit was not powered when I took the measurements. I powered it up to set the trim pot. And then powered down to measure the resistance across the trim pot.
Less resistance, less current???
Depends on which end of the divider the trimmer is on. Did you measure the voltage across the trimmer at different settings?
edgemoron:
Depends on which end of the divider the trimmer is on. Did you measure the voltage across the trimmer at different settings?
One side and the trimmer are connected. There is a miniscule (0.1 ohm) amount of resistance between them on my meter regardless of setting. This is, of course, the way it was made.
I know it doesn't make sense to me. Wish it did. But it doesn't.
I know it doesn't make sense to me.
It would make sense if you knew where that resistor was in the overall circuit. Basically a trim pot allows you to set a voltage, and it is this voltage that interacts with the rest of the circuitry to produce the required current. This trim pot is not passing the current for the LED through it. It can make no sense to you because you don't know what the rest of the circuit is. It only makes sense to us because we can imagine several circuits where this is what you would see.
Grumpy_Mike:
It would make sense if you knew where that resistor was in the overall circuit. Basically a trim pot allows you to set a voltage, and it is this voltage that interacts with the rest of the circuitry to produce the required current. This trim pot is not passing the current for the LED through it. It can make no sense to you because you don't know what the rest of the circuit is. It only makes sense to us because we can imagine several circuits where this is what you would see.
Point taken.