voltmeters

The voltmeter - meter direct reference for determining the voltage or voltage in electrical circuits, as is the voltage Measurement units - volts (V), the indications specified in volts
. Connected parallel to the load or source of electrical energy.
Ideal voltmeter should have an infinitely large internal resistance. Therefore, the higher the internal resistance of the voltmeter real, the less influence renders the device on the object being measured and, consequently, the greater the accuracy and variety of applications.

Classification and principle of action
By the principle of action voltmeters are divided into:
electro - magneto, electromagnetic, electrodynamic, electrostatic, AC-DC converters, thermometers;
e -. analog and digital
By appointment: DC, AC, pulse, phase-sensitive, selective, universal
. According to the construction and method of application: shield, portable, stationary and laboratory

Analog electromechanical voltmeters
Magnetoelectric, electromagnetic, electrodynamic and electrostatic voltmeters are measuring mechanisms showing respective types of devices. To increase the limit of measurement used sequentially included additional resistance. Technical characteristics of the analog voltmeter is largely determined by the sensitivity of the magnetoelectric measuring device. The smaller the current full deflection, the more high-resistance series resistor can be used. This means that the input impedance of the voltmeter will be higher.
Rectifier voltmeter is a combination measuring device that is sensitive to direct current (typically magnetoelectric) and the rectifying device.
Thermoelectric voltmeter - a device that uses electromotive force by one or more thermocouples heated input current

Analog electronic voltmeters general purpose
Analog Digital voltmeters contain, in addition to the magnetoelectric measuring device and the additional resistances, measuring power (AC or DC), that allows to have lower measurement limits (up to tens - millivolts and lower units), significantly increase the input impedance of the device, to receive the linear scale at low within the measuring AC voltage.

Digital electronic voltmeters general purpose
The principle of operation of voltmeters discrete action is to convert the measured DC or slowly varying voltage electrical code using the analog-to-digital converter, which is displayed on the scoreboard in the digital form.