Transformer Based Current Sensor Test

In this video we take a look at a transformer based current sensor from AllieExpress. i bought this thing for about a dollar thinking it would be fun to play with. There are no active components here, only a transformer and some header pins. I was unable to get a reliable reading in either DC or AC current.

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[learnelectronics]

Get solderstick at 20% OFF with discount code "LE20" at www.solderstick.com/sale"

[Dronebotworkshop]

Paul, these current transformers are designed for AC, not DC, as they work via induction. That's why you saw that brief reading when you first turned it on. To take a non-contact reading of DC current, you would use a different type of sensor, such as a hall-effect sensor, that measures magnetic fields.

[PhoenixRevealed]

At the end your meter is set to DC. It needs to be on ACV mode.

[edisont.picard]

Your meter was set on DC volts. If you were putting AC through the resistor, then AC would be coming out of the transformer. Your meter wasn't set to AC volts.

[Kteknik.]

Current transformer = Current in- Current out, your current in is the wire going thrugh the hole, current out is the two pins from the device on the pcb.
Never let a current transformer operate with an open output, so put a load on it.
And as other points out, AC.
The data on that current transformer could look like, 5A max, 1000:1, shunt resistor 200 ohm, 20-2000 Hz.
So place a 200 ohm resistor over the output pins and then measure the voltage in ac. 1 volt @ 5A.

[nigeljohnson]

I think the problrm is your meter appeared to be set to DC voltage. This is a transformer, so AC in gives AC out.
There is a lot of scope for building output circuits, both for measurement and triggering.

[garydirkse]

Try setting meter to ac milliVolts, then increase the current. I use a current transformer that has a 500 to one turns ratio so, one Ampere yields only two milliAmperes out. Many others will give you about 10 mV out per Ampere

[Roman.Pavelka]

Many pointed out mistakes here already: It works for AC only, it is a transformer. Also there will be current ratio, 1:1000 means that 5 A AC would get to 5 mA AC. This is to be added with an resistor to measure voltage on it, I would use something like 100R to get 500 mV signal for full range. It seems that some resistor is already provided on the board, check that as well. You can not measure it in circuit, because then you would measure also coil resistance in parallel... I am building the meter to be used for rush in current for large SMPS, these things works...

[Enigma]

I wonder if 2ma is too low to effectively detect. The max current rating on these is 5A. As a suggestion, you could try passing one leg of a line power card through it with the device being on. For example, a 60W bulb would draw about 1/2A.

[davidh]

DVM set to DC volts won't measure AC volts. Also note that you are running at 10kHz. Measuring directly out of my FG, 24v at 10kHz gives a vAC reading of 4v. At 60Hz it is 8.5vAC

[rcard-ehqi]

Current transformers.have a rating mv per Amp. So a common one is 1mv per Amp. So for every amp of current you put on you get 1mv of voltage out. Also a thing you can do is put the output of the current transformer into your scope and you will be able to see the AC sine wave on your display when you turn your current on. But only if the current through the transformer is sufficient to generate a readable voltage signal

[bblod]

A magnetic field develops along the wire when energized and that same field collapses when de-energized The coil picks up the expanding and collapsing magnetic field which creates a difference of potential in the coil.
You can do the same thing with an ignition coil and 12 vdc. But be careful, that can hurt.
☮️ Brother

[hellosir]

Not sure if the header pins & mod plug are common. Try to mod plug, you were reading continuity there. Also meter is set to DC vlt.

[FanicaBotezatu]

TA12-100 transformation ratio is 1000:1 , input current is 0-5A and output current is 0-5mA

[rcard-ehqi]

I found one on eBay it is a 1000 to 1 transformer. 5 amps in equals 5 ma out. Try increasing the current through your transformer.

[JohnKnutsson]

Try using a scope in AC mode instead of a meter

[karljay]

I don't have a good answer for this sensor, but I'd like to make a video suggestion: I just bought a pocket scope and want to protect it from voltage/current spikes. Is there a good scope probe add on circuit that can protect a cheap scope from blowing up as I probe around things like car amps and stuff?

[harryshector]

As edisont.picard commented below, current transformers are A.C. only devices. Additionally, you did establish continuity between the current xformer and the connector pins, but you didn’t show continuity through the xformer coil itself. I wouldn’t expect super accuracy from a component such as this, which cost only a dollar. The markings on the case may give a clue to the sensitivity… Or, they may not. But, once you have established that you have a coil, you can work out the sensitivity by experiment.

[frankowalker]

Try using an AC transformer instead of a signal generator. (?)

[jfalbo]

When you get this figured out I hope you make another video. I agree with many I think a c v setting on meter.