ANALOG VOLTMETER
Indotech Analog Voltmeter – Analog Voltmeter is a voltage meter. Which measures the voltage between the two nodes. We know the unit of potential difference is volts. So it is a measuring instrument which measures the potential difference between the two points.
Indotech Analog Voltmeter use solid-state components and display values digitally. Typically, Analog voltmeter (analog voltmeter) can be used to locate excessive resistance that may indicate an open circuit or ground. They are also used to identify low voltage or voltage drops that may indicate a poor connection. The positive lead is connected to the circuits positive side and the negative lead is connected to the circuits ground. The analog voltmeters internal resistance is the impedance, which is usually expressed in ohms per volt. This amount is relatively high in order to prevent the device from drawing significant current and disturbing the operation of the circuit being tested. The sensitivity of the voltmeter determines the range of voltages that analog voltmeters can measure.
‘‘INDOTECH’’ Voltmeters have been found indispensable by Laboratories and Industrial Houses. All the components used in the manufacture of the instruments are selective and are designed to ensure long term accuracy and service. All parts/sub-assemblies are thoroughly inspected and gauged at all stages with utmost care by experts.
TYPE OF METERS : ANALOG VOLTMETER
The movements are strongly constructed incorporating synthetic sapphire jewel bearings, hard chrome plated highly polished pivots and phosphor-bronze cadmium copper hair springs. Moving coil meters are fitted with high flux density magnets resulting in linear scale. All these meters have zero adjuster accessible from the front.
MOVING COIL TYPE METERS :
Classification or Types of Voltmeter
According to the construction principle, we have different types of voltmeters, they are mainly –
- Permanent Magnet Moving coil (PMMC) Voltmeter.
- Moving Iron (MI) Voltmeter.
- Electro Dynamo meter Type Voltmeter.
- Rectifier Type Voltmeter
- Induction Type Voltmeter.
- Electrostatic Type Voltmeter.
- Digital Voltmeter (DVM).
These are meant for measuring AC quantities. However, DC quantities could also be measured but with slightly low accuracy. These are available in 90O movement.
Permanent Magnet Moving coil (PMMC) Voltmeter: When current carrying conductor placed in a magnetic field, a mechanical force acts on the conductor, if it is attached to a moving system, with the coil movement, the pointer moves over the scale.
Moving Iron Voltmeter:MI instruments mean moving iron instrument. It is used for both AC and DC measurements, because the deflection θ proportional square of the voltage assuming impedance of the meter to be constant, so what ever is polarity of the voltage, it shows directional deflection, further they are classified in two more ways.
Electro dynamo meter Type Voltmeter : Electro dynamo meter instruments are used because they have the same calibration for both AC and DC i.e. if it is calibrated with DC, then also without calibrating we can measure AC.
Moving Coil Rectifier Voltmeter Meter : Moving Coil instruments are meant for the measurement of DC voltages and currents. All the meters are fitted with high flux density magnets resulting in linear scale. These are available in both 900&2400 movements.
Electrostatic Instruments Principle : When electric field created by the charged particles are allowed to act on the conductors which is charged by the current, a deflecting torque is produced. This can be done by using-
- Two electrodes which are oppositely charged in which one of them is fixed and the other is movable.
- Force between two electrodes which causes rotary motion of the moving electrode.
Digital Voltmeters (DVM): The Digital Voltmeter is an instrument which can give the output voltage not by deflection but directly indicating the value. It is a very good instrument to measure the voltage as it eliminates completely the error due to parallax, approximation in measurement, high-speed reading can be done and it can also be stored in memory for further analysis. The main principle is that the value is measured by the same circuit arrangement but that value is not used to deflect the pointer, but it is fed to the analog to digital converter and displayed as the digital value.
SPECIFICATION : PARAMETER
Meters are available for the measurement of mV, V,mA & A, KV meters are calibrated in terms of PT ratio & high range Voltmeter in terms of CT ratio.
NOTE :
1. Mode l s SR72/MR72, SR96/MR96 & SR144/MR144 have changeable dial for different CT Ratios in case of Moving Iron Meters and different FSD for Shunt opreated meters in case of Moving Coil Meters of 90′ movements.
2. Dials for 2400 movement meters are not changeable.
TESTS : Following tests are performed as per BIS 1248-03
| Test | Result |
| VIBRATION TEST | The meters are subjected to vibrations. This test ensures that if there is any loose component, it will be detected before the meter is passed. |
| LIFE TEST | The meter is subjected from zero to full scale and the counter meter records the number of operations. |
| OVER LOAD TEST | The meter is over loaded 120% of its rated capacity for 2 hours. |
| HIGH VOLTAGE BREAKDOWN TEST | The meter should withstand 2kV, AC, if applied between electrical circuit and any metallic point of the meter for 1 minute. |
| INSULATION RESISTANCE TEST | BIS1248-03 specifies that the insulation resistance should be above 5 mega ohms. The test is performed accordingly. |
| ACCURACY TEST | The accuracy test is performed as per BIS 1248-03.The error is calculated on the basis of full scale deflection of the meter. |
