Solenoid voltmeter
Encyclopedia
A solenoid voltmeter is a specific type of voltmeter
used by electrician
s in the testing of electrical power circuits.
Wiggy is the registered trademark for a common solenoid voltmeter used in North America derived from a device patented in 1918 by George P. Wigginton.
or digital electronics, the solenoid voltmeter simply uses a spring
-loaded solenoid
carrying a pointer (it might also be described as a form of moving iron meter
). Greater voltage creates more magnetism
pulling the solenoid's core in further against the spring loading, moving the pointer. A short scale converts the pointer's movement into the voltage reading. Solenoid voltmeters usually have a scale on each side of the pointer; one is calibrated for alternating current
and one is calibrated for direct current
. Only one "range" is provided and it usually extends from zero to about 600 volts.
A small permanent magnet rotor is usually mounted at the top of the meter. For DC, this magnet flips one way or the other, indicating by the revealed color (red or black) which lead of the voltmeter (the red or the black lead) is positive. For AC, the rotor simply vibrates, indicating that the meter is connected to an AC circuit. Another form of tester uses a miniature neon lamp
; the negative electrode glows, indicating polarity on DC circuits, or both electrodes glow, indicating AC.
Models made by some manufacturers include continuity test lights, which are energized by a battery within the tester. This is particularly advantageous when testing, for example, fuses in live circuits, since no switching is required to change from continuity mode to voltage detecting mode.
The probes (test prods) are very sturdy and they can be stored within the meter's body. A probe may also be extended from the meter's body, allowing one hand to both probe and hold the meter in a useful position. Probes are usually securely or permanently attached to the unit, so leads are unlikely to slip out if the tester is dropped.
The solenoid voltmeter has no switches that can be set incorrectly, simplifying operation.
For "go/no go
" testing, there is no need to read the scale as application of AC power creates a perceivable vibration and sound within the meter.
Solenoid voltmeters draw appreciable current
when operating. This makes them useful for testing residual-current device
s (GFCIs
) because the current drawn will trip most RCDs when the solenoid voltmeter is connected between the live and earth conductors. Also, when testing power supply circuits, a high-impedance connection (that is, a nearly open-circuit fault such as a burned switch
contact or wire joint) in the power path might still allow enough voltage/current through to register on a high-impedance digital voltmeter
, but it probably will not actuate the solenoid voltmeter. For use with high impedance circuit applications, however, they are not so good, as they draw appreciable current and therefore alter the voltage being measured.
Some manufacturers include a continuity test lamp function in a solenoid meter; these use the same probes as the voltage test function. This feature is useful when testing the status of contacts in energized circuits - the continuity light will display if the contact is closed, and the solenoid voltmeter will show voltage presence if open (and energized).
, ohmmeter
, or capacitance meter); they are just simple, easy-to-use power voltmeters. Solenoid voltmeters are useless on low-voltage circuits (for example, 12 volt circuits). The basic range of the voltmeter starts at around 90V (AC or DC).
Solenoid voltmeters are not precise. For example, there would be no reliably perceptible difference in the reading between 220 VAC and 240 VAC.
They draw a moderate amount of power from the circuit under test and are meant for intermittent operation and will overheat if used continuously.
The low impedance and low sensitivity of the tester may not show high-impedance connections to a voltage source, which can still source enough current to cause a shock hazard.
Voltmeter
A voltmeter is an instrument used for measuring electrical potential difference between two points in an electric circuit. Analog voltmeters move a pointer across a scale in proportion to the voltage of the circuit; digital voltmeters give a numerical display of voltage by use of an analog to...
used by electrician
Electrician
An electrician is a tradesman specializing in electrical wiring of buildings, stationary machines and related equipment. Electricians may be employed in the installation of new electrical components or the maintenance and repair of existing electrical infrastructure. Electricians may also...
s in the testing of electrical power circuits.
Wiggy is the registered trademark for a common solenoid voltmeter used in North America derived from a device patented in 1918 by George P. Wigginton.
Operation
Rather than using a D'Arsonval movementGalvanometer
A galvanometer is a type of ammeter: an instrument for detecting and measuring electric current. It is an analog electromechanical transducer that produces a rotary deflection of some type of pointer in response to electric current flowing through its coil in a magnetic field. .Galvanometers were...
or digital electronics, the solenoid voltmeter simply uses a spring
Spring (device)
A spring is an elastic object used to store mechanical energy. Springs are usually made out of spring steel. Small springs can be wound from pre-hardened stock, while larger ones are made from annealed steel and hardened after fabrication...
-loaded solenoid
Solenoid
A solenoid is a coil wound into a tightly packed helix. In physics, the term solenoid refers to a long, thin loop of wire, often wrapped around a metallic core, which produces a magnetic field when an electric current is passed through it. Solenoids are important because they can create...
carrying a pointer (it might also be described as a form of moving iron meter
Ammeter
An ammeter is a measuring instrument used to measure the electric current in a circuit. Electric currents are measured in amperes , hence the name. Instruments used to measure smaller currents, in the milliampere or microampere range, are designated as milliammeters or microammeters...
). Greater voltage creates more magnetism
Magnetism
Magnetism is a property of materials that respond at an atomic or subatomic level to an applied magnetic field. Ferromagnetism is the strongest and most familiar type of magnetism. It is responsible for the behavior of permanent magnets, which produce their own persistent magnetic fields, as well...
pulling the solenoid's core in further against the spring loading, moving the pointer. A short scale converts the pointer's movement into the voltage reading. Solenoid voltmeters usually have a scale on each side of the pointer; one is calibrated for alternating current
Alternating current
In alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....
and one is calibrated for direct current
Direct current
Direct current is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through...
. Only one "range" is provided and it usually extends from zero to about 600 volts.
A small permanent magnet rotor is usually mounted at the top of the meter. For DC, this magnet flips one way or the other, indicating by the revealed color (red or black) which lead of the voltmeter (the red or the black lead) is positive. For AC, the rotor simply vibrates, indicating that the meter is connected to an AC circuit. Another form of tester uses a miniature neon lamp
Neon lamp
A neon lamp is a miniature gas discharge lamp that typically contains neon gas at a low pressure in a glass capsule. Only a thin region adjacent to the electrodes glows in these lamps, which distinguishes them from the much longer and brighter neon tubes used for signage...
; the negative electrode glows, indicating polarity on DC circuits, or both electrodes glow, indicating AC.
Models made by some manufacturers include continuity test lights, which are energized by a battery within the tester. This is particularly advantageous when testing, for example, fuses in live circuits, since no switching is required to change from continuity mode to voltage detecting mode.
Advantages
Solenoid voltmeters are extremely rugged and not very susceptible to damage through either rough handling or electrical overload.The probes (test prods) are very sturdy and they can be stored within the meter's body. A probe may also be extended from the meter's body, allowing one hand to both probe and hold the meter in a useful position. Probes are usually securely or permanently attached to the unit, so leads are unlikely to slip out if the tester is dropped.
The solenoid voltmeter has no switches that can be set incorrectly, simplifying operation.
For "go/no go
Go/no go
In general go/no go testing refers to a pass/fail test principle using two boundary conditions.The test is passed only when the Go condition is met and also the No go condition fails....
" testing, there is no need to read the scale as application of AC power creates a perceivable vibration and sound within the meter.
Solenoid voltmeters draw appreciable current
Electric current
Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...
when operating. This makes them useful for testing residual-current device
Residual-current device
A Residual Current Device is a generic term covering both RCCBs and RCBOs.A Residual-Current Circuit Breaker is an electrical wiring device that disconnects a circuit whenever it detects that the electric current is not balanced between the energized conductor and the return neutral conductor...
s (GFCIs
Residual-current device
A Residual Current Device is a generic term covering both RCCBs and RCBOs.A Residual-Current Circuit Breaker is an electrical wiring device that disconnects a circuit whenever it detects that the electric current is not balanced between the energized conductor and the return neutral conductor...
) because the current drawn will trip most RCDs when the solenoid voltmeter is connected between the live and earth conductors. Also, when testing power supply circuits, a high-impedance connection (that is, a nearly open-circuit fault such as a burned switch
Switch
In electronics, a switch is an electrical component that can break an electrical circuit, interrupting the current or diverting it from one conductor to another....
contact or wire joint) in the power path might still allow enough voltage/current through to register on a high-impedance digital voltmeter
Voltmeter
A voltmeter is an instrument used for measuring electrical potential difference between two points in an electric circuit. Analog voltmeters move a pointer across a scale in proportion to the voltage of the circuit; digital voltmeters give a numerical display of voltage by use of an analog to...
, but it probably will not actuate the solenoid voltmeter. For use with high impedance circuit applications, however, they are not so good, as they draw appreciable current and therefore alter the voltage being measured.
Some manufacturers include a continuity test lamp function in a solenoid meter; these use the same probes as the voltage test function. This feature is useful when testing the status of contacts in energized circuits - the continuity light will display if the contact is closed, and the solenoid voltmeter will show voltage presence if open (and energized).
Disadvantages
In contrast to multimeters, solenoid voltmeters have no other built-in functions (such as the ability to act as an ammeterAmmeter
An ammeter is a measuring instrument used to measure the electric current in a circuit. Electric currents are measured in amperes , hence the name. Instruments used to measure smaller currents, in the milliampere or microampere range, are designated as milliammeters or microammeters...
, ohmmeter
Ohmmeter
An ohmmeter is an electrical instrument that measures electrical resistance, the opposition to an electric current. Micro-ohmmeters make low resistance measurements. Megohmmeters measure large values of resistance...
, or capacitance meter); they are just simple, easy-to-use power voltmeters. Solenoid voltmeters are useless on low-voltage circuits (for example, 12 volt circuits). The basic range of the voltmeter starts at around 90V (AC or DC).
Solenoid voltmeters are not precise. For example, there would be no reliably perceptible difference in the reading between 220 VAC and 240 VAC.
They draw a moderate amount of power from the circuit under test and are meant for intermittent operation and will overheat if used continuously.
The low impedance and low sensitivity of the tester may not show high-impedance connections to a voltage source, which can still source enough current to cause a shock hazard.