Ammeters are devices that are used to determine the current strength in a circuit. Digital modifications are made on the basis of comparators. They differ in accuracy of measurement. It is also important to note that the devices can be installed in a circuit with direct and alternating current.
According to the type of design, there are panel, portable, as well as built-in modifications. There are pulse and phase-sensitive devices for their intended purpose. Selective models are highlighted in a separate category. In order to break into devices in more detail, it is important to know the device of the ammeter.
Ammeter circuit
A typical digital ammeter circuit includes a comparator along with resistors. A microcontroller is used to convert the voltage. Most often it is used with reference diodes. Stabilizers are installed only in selective modifications. Broadband filters are used to increase measurement accuracy. Phase devices are equipped with transceivers.
DIY model
It is quite difficult to assemble a digital ammeter with your own hands. First of all, this will require a high-quality comparator. The sensitivity parameter should be at least 2.2 microns. The minimum resolution he must withstand at a level of 1 mA. The microcontroller in the device is installed with reference diodes. The display system is connected to it through a filter. Next, to assemble a digital ammeter with your own hands, you need to install resistors.
Most often they are selected by the switched type. The shunt in this case should be located behind the comparator. The division ratio of the device depends on the transceiver. If we talk about a simple model, then it is used of a dynamic type. Modern devices are equipped with ultra-precise analogues. A stable current source can be a regular lithium-ion type battery.
DC devices
The digital DC ammeter is produced on the basis of highly sensitive comparators. It is also important to note that stabilizers are installed in the devices. Resistors are suitable only for switching type. The microcontroller in this case is installed with reference diodes. If we talk about the parameters, then the minimum resolution of the devices is 1 mA.
AC Modifications
The ammeter of the (digital) AC can be done independently. Microcontrollers in models are used with rectifiers. To increase the accuracy of measurements, filters of broadband type are used. The shunt resistance in this case should not be less than 2 Ohms. The sensitivity of the resistors must be 3 microns. Stabilizers are most often installed expansion type. It is also important to note that a triode is required for assembly. Solder it directly to the comparator. The permissible error of devices of this type fluctuates around 0.2%.
Pulse Measurement Instruments
Pulse modifications are distinguished by the presence of counters. Modern models are available on the basis of three-digit devices. Resistors are used only orthogonal type. As a rule, their division coefficient is 0.8. Allowable error, in turn, is 0.2%. The disadvantages of the devices include sensitivity to environmental humidity. Also, they must not be used at sub-zero temperatures. It is problematic to assemble the modification yourself. Transceivers in models are used only dynamic type.
Phase sensitive device
Phase-sensitive models are sold at 10 and 12 V. The parameter of the allowable error for the models fluctuates around 0.2%. Counters in devices are used only two-digit type. Microcontrollers are used with rectifiers. Ammeters of this type are not afraid of high humidity. Some modifications have amplifiers. If you are assembling the device, you will need switched resistors. A stable lithium-ion battery can be a source of stable current. A diode is not needed in this case.
Before installing the microcontroller, it is important to solder the filter. A converter for lithium-ion will require a variable type. The sensitivity indicator is at the level of 4.5 microns. With a sharp drop in voltage in the circuit, it is necessary to check the resistors. The division ratio in this case depends on the throughput of the comparator. The minimum pressure of devices of this type does not exceed 45 kPa. The current conversion process itself takes about 230 ms. The clock speed depends on the quality of the counter.
Selective Device Diagram
A selective digital DC ammeter is manufactured on the basis of high throughput comparators. Permissible error of the models is 0.3%. Devices work on the principle of one-step integration. Counters are used only two-digit type. Sources of stable current are installed behind the comparator.
Resistors are switched type. For self-assembly of the model, two transceivers will be required. Filters in this case can significantly improve the accuracy of measurements. The minimum pressure of the devices lies in the region of 23 kPa. A sharp drop in voltage is observed quite rarely. Shunt resistance, as a rule, does not exceed 2 Ohms. The current measuring frequency depends on the operation of the comparator.
Universal measuring instruments
Universal measuring instruments are more suitable for domestic use. Comparators in devices are often not set very sensitive. Thus, the permissible error lies in the region of 0.5%. Counters are used three-digit type. Resistors are used on the basis of capacitors. Triodes are found both phase and pulse type.
The maximum resolution of the devices does not exceed 12 mA. The resistance of the shunt, as a rule, lies in the region of 3 ohms. Permissible humidity for devices is 7%. The pressure limit in this case depends on the installed protection system.
Panel models
Panel modifications are made on 10 and 15 V. Comparators in devices are installed with rectifiers. The permissible error of the devices is at least 0.4 5. The minimum pressure of the devices is about 10 kPa. Converters are used mainly of variable type. For self-assembly of the device can not do without a two-digit counter. Resistors in this case are installed with stabilizers.
Embedded Modifications
The digital built-in ammeter is produced on the basis of reference comparators. The throughput of the models is quite high, and the permissible error is about 0.2%. The minimum resolution of the devices does not exceed 2 mA. Stabilizers are used both expansion and pulse type. Resistors are installed high sensitivity. Microcontrollers are often used without rectifiers. On average, the current conversion process does not exceed 140 ms.
DMK Models
Digital ammeters and voltmeters of this company are in great demand. The assortment of this company has many stationary models. If we consider voltmeters, then they withstand a maximum pressure of 35 kPa. In this case, the transistors are of the toroidal type.
Microcontrollers are usually installed with converters. For laboratory tests, devices of this type are ideal. Digital ammeters and voltmeters of this company are manufactured with protected cases.
Torex device
The specified ammeter (digital) is produced with increased current conductivity. The device withstands maximum pressure of 80 kPa. The minimum permissible temperature of the ammeter is -10 degrees. The specified measuring device is not afraid of high humidity. It is recommended to install it near a current source. The division ratio is only 0.8. The ammeter (digital) withstands maximum pressure at 12 kPa. The current consumption of the device is about 0.6 A. The triode is used phase type. For domestic use, this modification is suitable.
Lovat device
The indicated ammeter (digital) is made on the basis of a two-digit counter. The current conductivity of the model is only 2.2 microns. However, it is important to note the high sensitivity of the comparator. The display system is simple, and it is very comfortable to use the device. The resistors in this (digital) ammeter are set to a switched type.
It is also important to note that they are able to withstand heavy loads. The shunt resistance in this case does not exceed 3 ohms. The current conversion process is pretty fast. A sharp voltage drop can only be associated with a violation of the temperature regime of the device. The permissible humidity of the indicated ammeter is as much as 70%. In turn, the maximum resolution is 10 mA.
DigiTOP Model
This digital DC voltmeter ammeter is available with reference diodes. The counter is provided for a two-digit type. The conductivity of the comparator is at around 3.5 microns. The microcontroller is used with a rectifier. The sensitivity of the current is quite high. The power source is a regular battery.
Resistors are used in a switched type device. The stabilizer in this case is not provided. Only one triode is installed. Direct conversion of current occurs quite quickly. For domestic use, this appliance is well suited. Filters to increase measurement accuracy are provided.
If we talk about the parameters of the voltmeter – ammeter, it is important to note that the operating voltage is at 12 V. The current consumption in this case is 0.5 A. The minimum resolution of the presented device is 1 mA. The resistance of the shunt is located at around 2 ohms.
The division coefficient of the voltmeter-ammeter is only 0.7. The maximum resolution of this model is 15 mA. The current conversion process itself takes no more than 340 ms. The permissible error of the specified device is at the level of 0.1%. The system withstands minimum pressure of 12 kPa.