Ammeter Precautions When using in Circuit

Ammeter Precautions When using in Circuit

PRECAUTIONS WHEN USING A VOLTMETER & AMMETERS

• Observe the correct polarity.
• Wrong polarity causes the meter to deflect against the mechanical stop and this may damage the pointer.
• Place the voltmeter across the circuit or component whose voltage is to be measured.

 

• When using a multi range voltmeter, always use the highest voltage range and then decrease the range until a good up-scale reading is obtained.
• Always be aware of the loading effect.

 

• The effect can be minimized by using as high a voltage range as possible. The precision of measurement decreases if the indication is at the end of the scale.

Probable Causes- 

1. Discontinuity in measurement terminals,
2. selector switch,
3. attenuator or the shunt; or
4. A fault PMMCC movement.

PRECAUTIONS WHILE USING AN AMMETER

• Never connect an Ammter across a source of emf.
• Because of its low resistance it would draw damaging high current and destroy the delicate movement.
• Always connect an ammeter in series with a load capable of limiting the current.

 

• Observe the correct polarity.
• Reverse polarity causes the meter to deflect against the mechanical stop and this may damage the pointer.

 

• When using a multi range meter, first use the highest current range, the decrease the current rage until substantial deflection is obtained.

 

• To increase accuracy of the observation, use the range that will give a reading as near to full-scale as possible.

       Probable causes-

• Faulty circuit,
• Open load,
• High resistances,
• Open connections of shorts meter terminals.