Clive W. Humphris

**ANALOGUE MULTI-METER: Measuring Voltage. (Voltmeter) **

To enable an analogue meter movement to measure voltages greater than its designed capability, a resistor needs to be inserted in series to limit the current flowing through the meter coil, to that which produces a full scale needle deflection (FSD).

A typical circuit diagram is shown in the lower half of the display which has four voltage ranges. 1Volt, 10V, 100V and 1kVolt. In practice these would be switched positions from a single input.

Each of the series resistor values is calculated using the formula shown. Here you can experiment with not only different voltage ranges, but also various values for the meter movement.

Suppose you are measuring 50V and using our values for FSD and Ra. You would select the 100V input. The total circuit resistance would be 999k + 1k = 1Mohms. Therefore the current would be 50 ÷ 1000,000 = 50µA = half full scale deflection. Note. The total meter circuit resistance (Rm + Ra) always equals input voltage range ÷ the current required to give a full scale needle deflection on the meter.

- Table of Contents
- Interactive eTextbooks
- Basic Electronics
- Conductor And Insulator
- Resistor Value Test
- Simple Dc Circuits
- Types Of Switching
- Variable Voltages
- Ohm's Law
- DC Voltage
- DC Current
- Series and Parallel Resistors
- AC Measurement
- AC Voltage and Current
- AC Theory
- RCL Series
- RCL Parallel
- Capacitance
- Capacitors
- Inductance
- Inductors
- Impedance
- Radio and Communication
- Tuned Circuits
- Attenuators
- Passive Filters
- Active Filters
- Oscillators
- Circuit Theorems
- Complex Numbers
- DC Power
- AC Power
- Silicon Controlled Rectifier
- Power Supply
- Voltage Regulation
- Electro-Magnetism
- Electrical Machines
- Transformers
- Three Phase Systems
- Energy Transfer and Cost
- Atomic Structures
- Diode Theory
- Diode Applications
- Transistor Theory
- Bipolar Transistors
- Transistor Configurations
- Active Transistor Circuits
- Field Effect Transistors
- Basic Operational Amplifier
- Op-Amp Theory
- Op-Amp Applications
- Sum and Difference Amplifiers
- Analogue Multi-Meter
- Component Testing