Multimeters are mobile measuring devices that can be universally used for various types of electrical measurements. Common applications include voltage, resistance and current measurements. Which different multimeters can be used to measure current and what you have to pay attention to in each case, we have summarized compactly in this blog post. You will also find handy multimeter instructions.
What is a multimeter?
When we talk about a multimeter, we are talking about a universally applicable measuring device for various electrical quantities. By the way, this is where the name comes from: “Multi” simply stands for the fact that different measurements can be performed. Not least because of this, it can also be used in diverse applications ranging from hobbyist use in a wall socket to resistance determination of circuits in a professional environment.
Multimeters can differ from each other depending on the manufacturer and model, but are often built.Thus, they have sockets for the mass connection and an adjustable measuring range, which is used to specify the type of measurement. In addition, a display is provided, which is an important distinguishing feature between analog and digital multimeters.
Analog multimeters have a visible scale in the display area that shows the measured value with the aid of a pointer deflection. This does not always go in the same direction, but is mostly installed from left to right. This scale has the advantages that even the smallest changes in the measured value can be followed live and a pulsable voltage can be detected directly.
A disadvantage, however, can be that the probability of reading errors increases and the measuring accuracy can also be limited by the scale division. If the measuring range changes, this must be set manually. Lateral viewing angle errors are meanwhile compensated by most manufacturers with reflective surfaces.
In contrast, there are digital multimeters that perform an automatic measurement and show the corresponding value via a display. Even with a high input voltage range, reading errors are very unlikely and any polarity is also directly detected and adjusted by the device. These models are also much cheaper, which is why analog multimeters are rarely bought anymore.
Measure current flow: Use multimeter
Not all current flow is the same – in fact, there are a number of quantities in the electrical field that can be measured with the multimeter. This includes the three different types of current flow: direct current, alternating current and mixed current. Both volts and amps can be measured with the multimeter. In addition, there are other measured values, which often include the following:
|Attention: The setting of the measuring range must be adapted to the current intensity to be measured and must never be smaller than the expected current intensity. Otherwise, the device may be damaged.|
- Current: An electric current flows when two poles of a voltage source are connected together in conductive form via a load. Therefore, electrons must be injected into the circuit. The current level depends on the voltage level and the resistance of the load.
- Voltage: Voltage, on the other hand, is the difference between the excess of electrons at the negative pole and the shortage of electrons at the positive pole. Therefore, the voltage is considered to drive the electric current. The higher the electron difference, the higher the voltage.
- Resistance: Resistors are marked with the formula symbol R and specified in ohms. They indicate how much voltage is required to move a given amount of charge through an electrical conductor. Therefore, the resistance depends on the diameter and conductivity of the conductor.
- Capacity: The term “capacity” is used to describe how much electrical energy can be stored at a given voltage. This can be related to a capacitor, for example.
- Temperature: Some digital multimeters also offer the possibility to determine the temperature with the help of a special probe. These probes are mostly made of nickel-chromium-nickel.
- Frequency: How often a signal oscillates around a mean value per second can be determined by many multimeters when measuring frequency. Both positive and negative oscillations are always taken into account.
Symbols for setting the multimeter
It is important that the setting in the measuring range must be made before the measurement. This must be adapted to the current to be measured on the multimeter and must never be less than the expected value – otherwise the multimeter may be damaged. Common symbols that are present on the device for adjustment are, in particular, these:
|V or two lines, where one is dashed||DC (DC voltage in volts)|
|V or a curved line||AC (alternating voltage in volts)|
|A or two lines, where one is dashed||Direct current (in amperes)|
|A or a curved line||AC current (in amperes)|
|Ω||Resistance (in ohms)|
|Arrow with line in front of the tip||Testing of the diode necessary|
|Point with sound waves||Testing of the passage necessary|
|Lateral “T” and rounded arrow||Measurement of the capacitance of the capacitor.|
|Hz||Measurement of the frequency (in Hertz)|
Measuring current with the multimeter: Instruction
But how can current be measured with the multimeter? Although there are different models, most devices are easy to use and help with a suitable multimeter labeling and various adjustable modes. It is important to set the measured variable and the measuring range optimally first. For example, A stands for amperes and must be selected if, for example, the amperes are to be measured with the multimeter.
Meanwhile, there are also some devices that have an auto-range finderand determine the measuring range automatically. However, this is not the rule, so it often has to be set manually. If there are uncertainties, larger values should be selected first, from which you can slowly feel your way down.
Measure the current voltage with the multimeter (U)
One of the common applications of measuring current with a multimeter is determining a voltage. In the case of a parallel connection, it is the same at all points, which is why the device can simply be connected in parallel with the source or the object being measured.
Select a suitable measuring range in volts (V) and opt for a larger value in case of uncertainties. Then connect the black measuring cable to the COM socket and the red measuring cable to the V socket before applying the test probes.
Measure the current with the multimeter (I)
If, on the other hand, a current is to be measured, the multimeter must first be connected in series – after all, this is a series connection and no longer a parallel connection. Turn the switch to A (amps) and connect the measuring cables in the same way as before.
After that, two measuring points must be created by breaking the circuit. The circuit to be measured must be voltage-free. After disconnection, the power supply can be reconnected and the test probes can be held to the points in the circuit. Alligator clips are best for this, as they clamp onto the desired wires quite easily.
Measure the resistance of a circuit with the multimeter (R)
When measuring the resistance of a circuit, the multimeter calculates the desired value R by dividing the voltage (U) by the current (I). For this purpose, a small measuring current is sent through the resistor so that the voltage drop can be used as a calculation variable. The voltage source is provided by the device battery.
Set the multimeter to the Ohm sign (Ω ) and connect the two measuring cables by connecting the black cable to the COM socket and the red cable to the Ohm socket. Then provide a voltage-free circuit and measure the resistance with the test probes between two selected points.
|Tip: You don’t always have to measure current with a multimeter. In larger plants, a current clamp is particularly suitable for lines.|
Tips for current measurement with the multimeter
To ensure that the measurement of amperes, current consumption and co. is optimally successful, some important precautions should be taken when handling the multimeter. In this way, errors can be avoided – and this in turn contributes to a correct measurement result and prevents damage to the device:
- Operating instructions: The best tip is always to take a look at the operating instructions before use. Not all instructions apply perfectly to all devices, so the manufacturer’s instructions should always be kept in mind.
- Determine sockets: Measurement errors (for example negative values) often occur when the input and output sockets have been reversed. This mistake can also be easily avoided by checking.
- Measuring range: It is important to set the correct measuring range before measuring with the multimeter. If this is unknown, start in the highest measuring range and work down slowly.
- Measuring tips: In addition, safe test leads may only be used with suitable test prods.
- Larger installations: Multimeters are not the only measuring devices that can be used to determine current and voltage. Especially in large plants it is worthwhile to use current clamps instead. These enable simple measurement, as they operate contactless and potential-free.
Multimeters for measuring current are to be operated carefully
Multimeters are characterized by many positive features. This includes the fact that they are particularly easy to operate and provide accurate measured values – provided they are operated correctly and carefully. Therefore, gives thoughtfulness in dealing. If you prepare for the measurement and take a look at the operating instructions to measure current correctly with the multimeter, you are on the safe side.
The best way to measure with a multimeter depends on the type of measurement. In all cases, however, the measuring range must be set and the type of measurement selected. In addition, the measuring cables must be connected to the correct sockets.
To measure a current flowwith the multimeter, the black measuring cable must be connected to the COM socket and the red measuring cable to the ampere socket. The correct measuring range is then set before the measuring tips can be held to the current source.
Most power cables have an outer conductor (brown or black), a protective conductor (yellow) and a neutral conductor (blue or gray). Current is carried by the outer conductor, which is also referred to as the phase. The protective conductor provides grounding, while the neutral conductor carries the current back to the power source.
A current voltage is measured by setting the multimeter to volts and selecting a suitable measuring range. Then the black measuring cable is connected to the COM socket and the red measuring cable to the V socket. The test probes are held at the two points between which the voltage is to be determined.
To measure a voltage drop, the correct measurement type must be selected on the multimeter (AC or DC). This is followed again by the setting of the measuring range. After that, the voltage measurement must be made in parallel with the consumer.
When measuring alternating current, the difference is that a different setting must be selected on the instrument. Otherwise, the red measuring cable is reconnected to the Ohm socket and the measurement is performed as usual.