How to measure amperage of LED lights

I have Bridgelux EB LED strips with a HLG-320H-C2800A. I’m turning the Potentiometer down a bit but I have no idea what current I’m using. I have an ammeter, but not sure how to measure the current.

Do I add wire to the positive and negative wire nuts (wago in this case) and touch the probes of the ammeter to it?

With an ammeter, you have to insert it in “series” with the LED, not in parallel. In other words, you’d have to insert it between the potentiometer and the LED and make it act like a “wire” that goes between these two. Here is a diagram I made quick to help visualize:


Hi @tilopa108,

Kaleb is correct that an ammeter must be placed in series with the circuit to measure current. He just didn’t realize that the HLG-320H-C2800A has a built-in potentiometer.

So you can use his diagram and just omit the potentiometer from the circuit. Connect the red lead of your ammeter to the positive output of the HLG-320H-C2800A and connect the black lead to the positive input of your LED strip. Connect the negative lead of your LED strip back to the supply and then you can apply power.

Make sure your ammeter is set to the right scale, as some of them use a low current fuse for low milliamp currents and a higher current rated fuse for measuring higher currents. If it is in the wrong range, you may blow the ammeter fuse.

1 Like

Sorry for the delayed reply. I just got around to trying to measure the current, and it didn’t work for me, zero on the meter.

One thing I should explain, I have 15 led strips connected in 3 sets of 5 in series, so 5 series together and each set of 5 is paralleled together. And, I put the red lead of ammeter to the positive output wire (coming out of the driver). And the black lead is on that same positive wire where it connects to the strips that are paralleled together. I’m using wago lever nuts and I have 3 positive wires and the positive output (from the Driver) wire wagod together. This is where I am putting my black ammeter probe.

Am I doing something wrong?

Here is a poorly drawn diagram of my wiring.

Hi @tilopa108,

Sounds like you are trying to measure in parallel with the positive lead wire, which is what you would do if you were trying to measure the voltage drop across the wire rather than the current running through it.

To measure current, you must place your leads in series with the wire, so you must disconnect either your positive lead or your negative lead and put your test leads in line with the circuit.

CAUTION: Your LED driver can output up to 118Vdc, which enough to cause SERIOUS harm. DO NOT TOUCH WHEN LIVE

So, in your circuit, before powering up, disconnect the “+” wire coming from the LED driver and connect the “+” lead from your ammeter to the LED driver. Then connect the “-” lead from your ammeter to the “+” input wire which goes to the “+” Wago connector. Make sure your ammeter is set to the right scale and that the leads are connected correctly on your meter (most multi-meters use different connections when measuring current rather than voltage). Once you have double-checked your connections, and ensuring that you are not touching any live wires or contacts, you can apply power and measure the current.

If interested, you can also measure the current in each of the three branches by following the same procedure. Just disconnect the lead going to any one of the three branches and put your ammeter leads in series there. The currents should be very similar between the three branches, but they may not be identical, due to variances in characteristics of each LED strip.

Thanks. I get what I did now, connecting parallel instead of series. It worked this time. I did have to switch my positive lead to the other port on the ammeter that said DC10A.

Strangely, the reading for my HLG-320H-C2800A is 3.24A when I turn the potentiometer to max, yet the datasheet says that the current adjustment is from 1.4 - 2.8. Maybe I need to ask Meanwell this question but I’m assuming that this is an error in reading from my device, if so what could be causing this?

Hmm, that does not sound right. It should max out right near 2.80A. I would double check how you reading it, and possibly see if you can use a different meter to see if you get the same results.

Yeah, I just have one of those cheap multimeters, I’ll try it with a better one later. Thanks.

Measurement error is very much a possibility, but some measure of slop in the output current range specification in to be expected; the datasheet indicates the adjustment range over which the device is stated to function; in order to meet that spec, the hardware will often have capabilities which exceed it by some margin, at least in some regions of its operating range.

Does that mean that it is possible that my device was accurately reading a current of 3200mA? If so that could be dangerously high for my LEDs, or at least could create a heat issue. I did dim them down to about 2700mA, so I should be ok. But my goal is to get them to 2100mA which I think is optimal efficiency.