Page 295 - Electrician - TT (Volume 1)

ELECTRICIAN - CITS

• Deflecting torque is produced due to the interaction of fields produced by fixed and moving coil field
• Deflecting torque is proportional to square of the current.
When it is used as volt meter or ammeter, its scale will be non
Dynamo meter instrument as an ammeter

This instrument could be used as milli or micro ammeter by connecting the fixed and moving coil in series
Dynamo meter instrument as an ammeter
For measuring large current, a moving coil is connected across a shunt
Dynamo meter instrument as a volt meter
The instrument is used as a volt meter,the fixed and moving coils are joined in series along with a high value
resistance (multiplier)

Digital Ammeter

Objectives: At the end of this lesson you shall be able to:
• state the features of digital ammeter
• state the movements, special operation and standard.

Digital Ammeter

Digital Ammeters are instruments that measure the current in ampere and display it in digital. These instruments
provide information about current drawn and current continuty to help users troubleshoot electric loads.
They have both positive and negative leads and low internal resistance. Digital ammeters are connected in series
with a circuit so that current flow passes through the meter.
It can be used to measure the A.C and D.C. Many digital ammeters include a current sensor built in the meter.
Features:
Different types of digital ammeters can measure different ranges of A.C current and D.C current and also A.C
frequency.
Batteries are provided in it to operate without plug-in-power and suitable for cutdoor use Fig 1 shows a typical
digital ammeter.
Standards :
Digital ammeters must have a certain standards and specifications to ensure proper design and functionality refer
IEC 600 51 - 2.

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CITS : Power - Electrician & Wireman - Lesson 50-53