Diagnostic Instruments; Using A Multimeter To Check The Electrical Systems - Ducati Diavel Workshop Manual

Diagnostic instruments

11 - Diagnostic instruments

Using a multimeter to check the electrical systems

Introduction
This instrument allows you to measure resistance, voltages, and current values. Multimeters can be divided into two basic
types: analogue and digital display multimeter. An analogue multimeter has a pointer display. The dial is marked with the
scales to be used for measurement of the various parameters. Digital units are equipped with a dial that displays numbers
corresponding to the values of the measured parameters. The type of measurement to be carried out (voltage, current or
resistance) is set by means of a selector or by means of several different sockets in which to insert the two test probe
connector terminals. In certain cases it is essential to set the full scale value before proceeding. For example, in order to
measure a 12 V signal, you need to set a full scale that is close to this value (e.g. 15 V or 20 V). It would be illogical
to set a full scale value of 10 V; the same applies when setting current (Amperes) or resistance (Ohms). Sometimes the
instrument can set the required full scale value automatically. Never exceed the maximum value allowed by the tester
when measuring voltage or current signals.
Note
The DDS diagnosis instrument (Sect. 6 -13, DDS diagnosis instrument) can fulfil the function of digital multimeter.
Voltage measurement
Voltage measurements must be carried out by connecting the terminals of the tester in parallel to the load (e.g. to the
wires feeding a light bulb or a relay, the two battery terminals, or the two wires supplying power to a control unit).
Voltages can be constant over time (DC voltage) or variable over time (AC voltage). In the first case, it is important to
consider the negative and positive polarity of the application. It is therefore necessary to select on the multimeter the
type of voltage you intend to measure. (DC voltage is shown by the symbol = while AC voltage is denoted by ~).
Current measurement
Current measurements must be made by connecting the multimeter terminals in series with the load (e.g. disconnect one
of the wires feeding power to a light bulb and connect one terminal of the multimeter to the free end of wire and the
other terminal to the light bulb. When the lights switch is set to ON, the bulb will illuminate normally and the tester will
show the absorbed current, i.e. the amount of current passing through the wire. Warning: connections in series must be
made and removed only when the power is switched off. Never attempt to make or break a series connection when a
device is powered. Always make sure that the connection in series of the tester terminals on the electrical device is made
is a safe manner in such a way that it cannot be broken accidentally.
Measurement of resistance values and electrical continuity
Resistance measurements must be taken only when the electrical device or section of the circuit is not powered and
isolated from the main electric system (i.e. not connected to the main electrical system). These measurements can be
utilised to check the resistance value across several sensors. For example, after disconnecting the electrical wiring to the