A miniature Chinese voltmeter can simplify the process of measuring the voltage and the amount of current consumed on a power supply or homemade charger. Its cost rarely exceeds 200 rubles, and if you order it from China through partner programs, you can also get a tangible discount.
To the charger
Those who like to design chargers on their own will appreciate the opportunity to observe the voltages and amperes of the network, without the help of bulky portable devices. It will also appeal to those who work on expensive equipment, the operation of which can be adversely affected by a regular drop in mains voltage.
With the help of a Chinese ampere-voltmeter, which is no larger than a matchbox in size, you can easily monitor the state of the electrical network. One of the perceptible problems faced by newcomers to electricians can be the language barrier and different wire markings from the standard one. Not everyone will immediately understand which wire to connect to, and the instructions are usually only in Chinese.
Devices for 100 V / 10 A are very popular among independent designers. It is also desirable that the device has a shunt to refine the connection process. A tangible advantage of this device is that it can be connected to the power supply of the charger or to an independent battery.
* The voltage of the power supply of the ammeter, voltmeter should be in the range from 4.5 to 30 V.
The connection diagram is as follows:
- The black wire is a minus. It must also be connected to a minus.
- The red wire, which should be thicker than the black one, is a plus and must be connected to the power supply accordingly.
- The blue wire connects the load to the mains.
If everything was connected correctly, two scales should be highlighted on the display.
To the power supply
Power supplies play an important role, equalize the network readings to the desired state. If not properly operated, they can severely harm expensive equipment, causing overheating. In order to avoid problems during their operation, and especially in cases where the power supply is made by hand, it is advisable to use an inexpensive ammeter, voltmeter.
A variety of models can be ordered from China, but for standard devices operating from a home network, those that measure current from zero to 20 A, and voltage up to 220 V. Almost all of them are small-sized and can be installed in small power supply cases.
Most devices can be adjusted using built-in resistors. In addition, they are highly accurate, almost 99%. The scoreboard displays six positions, three for voltage and current. They can be powered either from a separate or from a built-in source.
To connect a voltmeter, you need to deal with the wires, there are five of them:
- Three thin. Black minus, red plus, yellow to measure the difference.
- Two fat ones. Red plus, black minus.
The first three cords are most often combined for convenience. The connection can be made through a special socket connector, or by means of soldering.
* The connection by soldering is more reliable, with slight vibrations, the socket mount of the device may come loose.
Step by step connection:
- It is necessary to decide from which power source the device will operate, separate or built-in.
- Black wires are connected and soldered to the minus PSU. Thus, a general minus is created.
- In the same way, you need to connect the thin red and yellow contacts. They are connected to the power contact.
- The remaining red contact will be connected to the electrical load.
If connected incorrectly, the instrument panel will show zero values. In order for the measurements to be as close as possible to the actual ones, the polarity of the supply contacts must be correctly observed. Only connecting the thick red wire to the load will give an acceptable result.
Note! Accurate voltage values can only be obtained from a regulated power supply. In other cases, the display will only show the voltage drop.
A popular voltmeter model that is often used by radio amateurs. Possesses the following characteristics:
- Operating voltage DC 4.5 to 30 V.
- Power consumption less than 20mA.
- The display is two-color red and blue. Resolution 0.28 inches.
- Performs measurements in the range 0 - 100 V, 0 - 10 A.
- The lower limit is 0.1 V and 0.01 A.
- The error is 1%.
- Temperature conditions of work from -15 to 75 degrees Celsius.
Connection
Using a voltmeter, you can measure the current voltage in the power supply network. To do this, you need the following:
- Connect the black thick wire to the minus of the power supply.
- Red is connected to the load, and then to the power supply.
This wiring diagram does not require the use of a thin black contact.
If a third party power supply is used, the connection will be as follows:
- The thick cords are connected in the same way as in the previous example.
- Subtle red connects to the plus side of a third party source.
- Black with a minus.
- Yellow with a plus source.
This voltmeter, ammeter is also convenient in that it is implemented in an already calibrated state. But even if inaccuracies were noticed in its work, they can be corrected using two tuning resistors on the back of the device.
What are the most reliable digital voltmeters
The electrical equipment market is overflowing with manufacturers who provide a wide variety of choices. However, not every device brings positive emotions from use. For a large number of products, it is not always possible to find a reliable and inexpensive copy.
Trusted and reliable voltmeters include:
- TC 1382. Inexpensive Chinese, the average price of which rarely rises above 300 rubles. Equipped with tuning resistors. Carries out measurements in the ranges 0-100 Volts, 0-10 Amperes.
- YB27VA. Almost a twin of the previous voltmeter, it differs in wire marking and a reduced price.
- BY42A. It is more expensive than previous models, but also has an increased upper measurement limit of 200 V.
These are the most popular representatives of this type of voltmeter, which can be freely purchased for alteration on the radio market or ordered via the Internet.
Calibration of Chinese voltmeter ammeter
Over time, any technique wears out. Since the operation of measuring devices is affected not only by their own faults, but also by failures in the connected devices, sometimes it is necessary to make adjustments.
Most models have special resistors on their case. By rotating them, you can redo the zero values.
All measuring devices have a measurement error, which is indicated in the documentation.
Conclusion
The inclusion of inexpensive voltmeters in the circuit avoids problems with inappropriate mains voltage. For a small fee, you can find out if the equipment is working under the right conditions. To connect them, you need to know the marking of all wires and the location of the plus and minus of the energy source.
Quite often in our life a situation arises in which we need to measure the current strength. For what? To find out the estimated power of a particular equipment, for example. To determine the potential level of heating of the cable, and so on. For approximately these purposes, we will need an alternating current ammeter. It is he who serves to measure the current strength. By the way, with the help of the device you can measure the strength of not only alternating, but also direct current. How do I use this tool?
To understand how to connect an ammeter, you need to understand the principle of the measuring range. That is, the instrument operates within a specific range, measuring from μA values to kA values. Taking into account the technical connection diagram, the maximum current level of the scale should be outstripped. The connection itself takes place in series, and not in parallel with the existing load. Otherwise, there is a danger of overvoltage of the device. Accordingly, it will become non-functional, in other words, it will burn out.
An important point is that the measured current is highly dependent on the total resistance of the circuit. It follows from this that the internal resistance of the device should be extremely small. Otherwise, the accuracy class of the results may be questionable. After all, the equipment itself will affect the numeral. To understand more precisely, you need an ammeter connection diagram.
Shunt
How to connect an ammeter if the amount of current required for measurement exceeds the capabilities of the device? For this, a variety of shunts are used. They allow you to expand the measurable current range. The load will be distributed in favor of the shunt, it will take over most of it. In fact, the shunt will simply show a decrease in current, which the device will fix. In this case, it will work on the principle of a millivoltmeter, however, its readings will be in amperes, which means that the final information will be correct.
For a more detailed understanding, a circuit for connecting an ammeter through a shunt is required.
Where is the ammeter used?
The DC ammeter is used everywhere. If we exclude household needs, then the first option would be large industrial enterprises. Naturally, only those who, in one way or another, are engaged in the creation (generation) and further consumption of electrical or thermal energy.
In addition, the device has found wide application in construction. No serious project goes without this little helper.
Variety of equipment
The ammeter device can be quite different depending on the model. If you classify them by the type of reference, you can distinguish arrow, light and electronic options.
A DC ammeter can be different as well as the way it functions. Here the row is wider, and it is worth dwelling on it in more detail.
Electromagnetic ammeters are necessary for measuring alternating current with a low frequency. The ammeter circuit of this type is the simplest, respectively - they are the cheapest on the market.
If you are wondering what is the name of a device for measuring high frequency current, then this is a thermoelectric meter. The principle of operation of an ammeter of this kind consists in the operation of a conductor and a thermocouple. The conductor, using the current passing through it, heats the thermocouple, which serves as a way to calculate the current strength.
Ferrodynamic devices are required for stressful environments with increased magnetic fields. They are more resistant to external and internal influences. The latest technology is the digital ammeter. These are the most progressive models that are not afraid of strong stress and mechanical damage. They are much easier to learn and use. How to connect a digital ammeter? In most cases, unless the manufacturer has indicated otherwise, just like the usual one.
On this, the main types of ammeters can be considered exhausted. Some users, however, think that we missed one view. Namely a voltmeter.
Differences between a voltmeter and an ammeter
First, let's just break down the etymology of words. It is immediately clear that the devices originated from the words "ampere" and "volt". And although the first one can be connected to the same circuit as the voltmeter, their purpose is completely different. Ampere is a unit for measuring current, while volt is a unit for measuring voltage. So how is an ammeter different from a voltmeter? That's right, the first measures strength, and the second measures tension.
We come across the measurement of current strength very often. In order to find out the power of the device, the cross-section of the cable for its power supply, the heating of wires and other elements - it all depends on the strength of the current. In order to directly measure this force, a device called an ammeter was invented. The ammeter is connected to the measured circuit only in series. Why? Let's take a look below.
As you know, the current strength is the ratio of the number of charges ∆Q that have passed through a certain surface during the time ∆t. In SI it is measured in amperes A (1 A = 1 C / s). In order to measure the amount of passed charges, the ammeter must be connected to the circuit in series.
To minimize the effect of the measuring resistance of the ammeter and, accordingly, reduce the power loss during measurement, it is made as small as possible. If an ammeter with such an internal resistance is connected in parallel, then a short circuit will occur in the circuit. An example of a wiring diagram:
Direct current is measured by devices in the range of 10 -3 - 10 2 A, electronic analog, digital, magneto-electric, electromagnetic, electrodynamic devices - milliammeters and ammeters. If the current is more than 100 A, a shunt is used:
Shunts are usually made for different currents. A shunt is a copper plate that has a certain resistance. When current flows through the plate, some voltage drops on it, according to Ohm's law U = I * R, that is, a voltage appears between points 1 and 2, which will act on the coil of the device.
The shunt resistance is usually selected from the ratios:
Where R and is the resistance of the measuring winding of the device, is the shunting coefficient, I is the measured one, and I and is the maximum permissible current of the measuring mechanism.
If an alternating current is measured, then it is important to know what value is being measured (amplitude, average, effective). This is important, since all scales are usually calibrated in terms of the effective values.
Variable values above 100 μA are usually measured with rectifying microammeters, and below 100 μA - with digital microammeters. For measurements in the range from 10 mA to 100 A, rectifier, electrodynamic, electromagnetic devices are used that operate in the frequency range up to several tens of kilohertz, as well as thermoelectric ones, the frequency range of which is up to hundreds of megahertz.
To measure variables from 100 A and above, devices are used, but using current transformers:
A current transformer is a device in which the primary winding is connected to a current source (or, as can be seen from the figure below, the primary winding is "put on" a bus or cable), and the secondary winding is connected to the measuring winding of a measuring device (the winding of a measuring device or sensor should have low resistance).
We all know that an ammeter is a device for measuring current, which is measured in amperes. It measures amperes, which means an ammeter.
But, in order to measure the current, it is necessary to correctly connect the ammeter to the circuit. Whether it is a DC or AC circuit. After all, incorrect switching on of the device can lead to its failure.
The ammeter is connected to the electrical circuit in series
That is, we have a wire, an electric current flows through it from the source of this very current to the consumer, which can be an electrical device.
To measure the current with an ammeter, we need to de-energize (disconnect) the power supply. Then you need to break the chain - literally and figuratively. Roughly speaking, cut the wire.
We now have two wires. We take an ammeter, connect two halves of the cut wire to the device. It is necessary to take into account the fact that the current flowing in the circuit must be less than the maximum measured current of the device. The maximum measured current of the device must be written on the device itself or in the documentation for it.
After the wires are connected and securely fixed in the ammeter, you can turn on the power and the device will show the amount of current in the circuit, which will pass through the ammeter.
But no one does this, because the cut wires do not lead to good.
The ammeter has a low internal resistance, this is done so that it minimally affects the value of the measured current. When connecting an ammeter to an alternating current circuit, it does not matter where to connect the device.
When connecting the ammeter to the DC circuit, if the arrow deviates in the other direction, or if it shows zero, the polarity should be reversed, the wires should be reversed.
Connecting an ammeter through a shunt
If the current in the circuit turns out to be greater than the current of the device, then a shunt can be calculated and used to measure the current of a larger value. In this case, the chain will split into two branches. One will have a small resistance of the ammeter, and the second will have a large resistance of the selected shunt. The large current will be divided in proportion to the resistances and a small current will pass through the ammeter, and a large one through the shunt. ().
Current measurement with an ammeter through a current transformer or clamp meter
There are times when you need to measure the current in a cable, on a bus ... an insulated bus. A tire is a strip of a certain section through which a current flows, not a car wheel ...
Cutting a cable or bus can be costly and pointless. In this case, you can use a clamp meter or a current transformer.
The current transformer has two windings - the highest and the lowest, which are not interconnected. The current comes to the highest one, then an EMF () is created and a current flows in the secondary winding proportional to the number of turns of the windings. So, if there is a need to measure the current, then a "donut" is hung on the cable, it is also a TT. And already. The main thing here is to be properly instructed and not to get things done. It turns out that we remove the current with an ammeter from the secondary winding, converted to the lower side and safe for measurement and ammeter.
The same principle is used in the measuring clamp, only the ammeter and the CT are in the same case. And on top of that, the primary winding of the tongs is opened at the touch of a button on the case and then closed.
Very often, novice radio amateurs ask the same question: - How to connect a universal Chinese voltmeter ammeter to a homemade charger or regulated power supply? Recently, I have been literally inundated with questions about how to connect, where to connect. Therefore, I decided to write a specially separate article in which I will tell you in detail how and how to connect a Chinese voltmeter ammeter to a charger or a homemade regulated power supply.
Today there are two popular Chinese, universal models of voltmeters ammeters with a built-in shunt, which all beginners and professional radio amateurs, without exception, love to buy in China on Aliexpress.
Let's take a closer look at two models of the most popular Chinese-made voltmeters and ammeters.
Both devices have five wires for connecting to the power supply. The first one on the left has three thick wires (black, blue, red) and two thin (black, red). Thin wires are designed to power the device: red plus, black minus. Thick wires: Black minus ammeter, blue ammeter output, red voltmeter input.
The second device also has five wires, three thin (black, red, yellow) and two thick wires (black, red). Thin wires are designed to power the device: red plus, black minus, yellow input of the voltmeter. Thick wires: black minus ammeter, red ammeter output.
Every Chinese universal measuring device (CUIP) has a built-in measuring shunt for an ammeter, and this is a big plus, because there is no need to "farm" anything, it is done according to the "set and forget" principle. In some KUIPs, the shunt is curved with the letter "M" and shiny, I got copies with a copper "P" shaped shunt. As I understand it, the shape and color of the shunt does not affect the quality of measurements.
The devices on the board have trimmer SMD resistors with which it is possible to correct the readings of the voltmeter and ammeter.
This figure shows a diagram of connecting a voltmeter of an ammeter of the first model to a charger from a computer power supply.
The device is powered from a separate power source, in this case it is a five-volt phone charger, which can be easily placed in the power supply case. The fact is that if you connect a voltmeter-ammeter to the regulated output of the power supply, then when the voltage drops below 4.5V, the device will simply stop working. The fan speed will also decrease, but at low voltage the radiators of the power supply unit will be a little warm and nothing terrible will happen.
With an output voltage of more than 12V, the L7812CV voltage stabilizer is turned on and thereby maintains a constant voltage on the fan of no more than 12V.
This figure shows a diagram of connecting a voltmeter of an ammeter of the second model to a charger from a computer power supply.
With a charger from a computer power supply, everything is clear. Let's look at the wiring diagram of a Chinese voltmeter ammeter of the first model to an adjustable power supply. The upper part of the diagram shows an adjustable power supply with short circuit protection, consisting of a diode bridge, a capacitor, an LM317 voltage regulator, an MJE13009 transistor, a variable resistor and three fixed resistors.
In the lower part of the circuit, the fan and the Chinese voltmeter ammeter are connected through the L7812CV voltage regulator to the output of the diode bridge in parallel with the capacitor C1. The stabilized voltage on the fan and control unit is not more than 12V.
This figure shows a diagram of connecting a Chinese voltmeter ammeter of the second model to an adjustable power supply.
Many radio amateurs prefer to install analog Chinese measuring devices (KIP) into chargers and regulated power supplies, which have not lost their popularity for many years. Therefore, I propose to consider the connection diagram of a classic dial voltmeter and ammeter.
This figure shows a wiring diagram for a voltmeter and ammeter with a built-in current-measuring shunt.
The voltmeter is connected in parallel to the power source, observing the polarity. There should be plus and minus marks on the device. The ammeter is usually connected to the gap in the negative wire after the voltmeter. You can also connect the positive wire to the break, the method of connecting the device does not affect the accuracy of measurements. The main condition is the observance of polarity.
Sometimes there are ammeters without a built-in current-measuring shunt. Then the shunt has to be bought separately. So that you do not have additional costs, before buying an ammeter, always check with the seller for the presence of a shunt inside the device. Sometimes the cost of a separate shunt is more than the cost of a device with an integrated shunt.
This figure shows a wiring diagram for connecting a voltmeter and ammeter with a separate current-measuring shunt to the power supply.
The shunt is always connected in parallel with the ammeter. Without it, the device will simply burn out. How to choose a shunt? If the device is rated for 10A, then the shunt must be 10A. Each shunt has a mark indicating what amperage it is rated for.
Well that's all, my article has come to an end, you now have new food for thought.
Friends, I wish you good luck and good mood! See you in new articles!
