AC Clamp Meter Uni-T UT202A toolboom.com/en/digital-clamp...
AC/DC Clamp Meter Uni-T UT203 toolboom.com/en/digital-clamp...
First let's find out what is clamp meter. It is a meter device capable of measuring current in a non-contact way. That is a main advantage of a clamp meter compared to traditional amperemeters or multimeters. You don't need to break the circuit to conduct measurements - you may actually conduct measurements of the line under voltage, as well as measuring high currents. Operation safety is one more advantage - you may measure current of the insulated conductor.
Measuring current with these meters is simple. You should switch to the required current measurement range (in our case it is 600 Amperes), press the trigger to open the jaws, and place the conductor under test inside and close the jaws. The display will show the measurement results.
The main element of a clamp meter is currents sensor. There are two types of sensors used: a current transformer or a Hall sensor. Depending on the sensor used the meter may measure either alternate current, or direct and alternate current.
So, the clamp meter with a current transformer:
In this meter, under this plastic lid, there is a magnetic core. If you open the jaws you may see parts of it. The role of a primary winding is played by the conductor that measures current, and the secondary winding is placed under the platic lid, we can not see it.
The main advantage of such kind of design is a rather low price and simplicity. The drawback is that it is a transformer, so you may measure alternate currents only.
Another type of design is a clamp meter with a Hall sensor. There is no magnetic core, if you open the jaws you may notice that. The advantage is that the Hall sensor is sensitive to both alternate and direct currents. And the disavantage is a higher price.
So, let's start with alternate current measurements. The main condition for measuring current is that you have to clench exactly the conductor that you need to measure. Like this. So if we clench both wides at a time or the wole cable, we will get a zero result beacause the meter will detect the difference between the currents. As both these conductors carry the same current - the difference will be a zero. So if you have a cable consisting of several wires and you need to measure each of them, you don't need to strip it like we have here, you just need to find a place where the cable is divided into separate wires, for example somewhere in the electric cabinet, and than start measuring.
And the second important condiition is setting the correct measurement range. If you are not sure about what is the current of the network, you have to start with the maximum range.
I will demonstrate this. Now I'll measure the current used to power the electric kettle. Let's imagine I don't know what current is used, but it has to be lower than 600 Amperes. I turn the kettle on and switch the meter to alternate current measurements within 600 Amperes range. Now I clench the wire. The kettle uses some current about 7 Amperes. I switch to a lower range - 200 Amperes, I get 7.6 Amperes. And to measure the current with the best accuracy I switch to 20 Ampere range - the meter shows 7.73 Amperes. If I clench both wires I'll get something about zero. You have to follow the rule of clenching one certain conductor.
Now I take the meter with a Hall sensor - the measurement procedure is similar. One difference is that you have to set the readings to zero before starting the new measurement, as the Hall sensor is magnetic sensitive. So I zero the display readings and measure - we've got a current slightly less than 8 Amperes.
Now I will use UT203 Clamp Meter to measure current in real-time conditions un a three-phase circuit.
And now I'm demonstrating the direct current measurements. We have a power supply unit providing 3 Ampere current in the circuit. I switch the meter to 40 Ampere range. As the Hall sensor is very sensitive we need to zero the display readings. And now we measure the conductor - it shows 3.15 Amperes. The absolute accuracy is about 150-170 milliAmpere, but it is not much taking into account that our measuring range is 40 A. AC clamp meter can not measure DC current at all.
These two models, as most of the modern clamp meters, apart from current, are capable of measuring AC/DC voltage, resistance, they have a continuity buzzer and diode test functions. These are fully functional multimeters with a non-contact current measurement function. I recommend you to watch the video “How to Use a Multimeter” where you may find a detailed demonstartion of these functions.
In this review I tried to answer the main questions that appear while using digital clamp meters. Thank you for attention and take care!