Multimeters

Galvanometer

An analog multimeter operating principles is based upon the galvanometers interaction of two magnetic fields.

2 Types of Multimeters

Analog & Digital

Test equipment that must be:

Calibrated annually at a minimum. Prior to using a multimeter check the calibration and its condition.

They load the:

Circuit

Bits and Counts Resolution

Defines the accuracy of DMM (Analog: Infinite # of measures DMM: finite amount)

Bearings

Desired to as friction-less as possible. Taught Band suspension is the best kind of bearing

DMM Construction

Display/Scale Pointer (analog) Mode/Function Control Ampmeter Voltmeter Ohmmeter Measurement Ports: (Com -), V/Ohms (+), A

Kirchoff's Law dictate

How we connect the multimeter

Multimeter Setup

Inspect Calibration Damage Select Model Range A Ohms V Connect Leads

All analog meters work off the principles of:

Magnetism (Galvanometer)

Multimeters

Many measures "I" "E" "R" are the most common (ampmeter, voltmeter, ohmmeter) AC/DC frequency Capacitors Diode checkers Semiconductors Temperature

High Sensitivity

Minimum load

What term is used to describe the calibrated resistance that is placed in series with a multimeters leads in order to extend the useful range when measuring voltage?

Multipliers

Sensitivity for analog meters is defined as:

Ohms/Volt

Voltmeters are set up in:

Parallel

Preparing a Circuit for Measurement

Remove power Set up multimeter Connect meter into the circuit Turn on circuit power ( "I" and "E" only! Not "R") Read measurement Turn off power Remove leads

Most Common Measurements

Resistance (1) Voltage (2) Current (3)

Analog Multimeter Parts

Scale Meter Movements: Pointer Movable coil Hair springs Bearings Magnets Shunts Multipliers Battery Leads

Quality is dictated by:

Sensitivity and/or resolution (Accuracy/Useful Range) Construction Features

Ampmeters are set up in:

Series

Ohmmeters are set up in:

Series or Parallel

What term is used to describe the calibrated resistance that is placed in parallel with a multimeters leads to extend the useful range when measuring current?

Shunts

When measuring the Ohms:

The multimeter provides the source of "I" to make measurements

Continuity

The presence of a complete path for current flow

Factors the will affect the appropriateness of a measurement

User Knowledge Ability DMM quality

Digital Multimeter

Works of microprocessor principles Input Decision (AND or NOT) Output Memory 3 1/2 digit display up to 1999 counts of resolution

DC

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