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TONEOHM 550A USER GUIDE
CAUTION: Disconnect power from the board under test before making
measurements with the TONEOHM 550A Shorts Locator.
Introduction
The TONEOHM 550A Shorts Locator is a precision milliohmmeter incorporating:
•
A resistance-dependent, variable-frequency audio tone output.
•
A liquid crystal display (LCD) screen providing an indication of the
resistance being measured.
The operator locates short circuits between two tracks of a printed circuit board by
connecting a probe to each track and listening for an audio tone. A tone indicates the
presence of a short circuit between the tracks. The frequency of the tone is dependent
on the resistance between the probes. Moving one of the probes along its track will
cause the resistance between the probes to change and cause a corresponding
change in the frequency of the tone. The probe is moved along the track until the tone
reaches its highest pitch, which is the position of the short.
Connecting the TONEOHM 550A to a power supply
Refer to the voltage label on the rear panel of the instrument and make sure that
the marked rating is suitable for the local mains power supply.
Check that the TONEOHM 550A mains switch (on the rear panel) is OFF. Plug the
power cable into the receptacle on the rear panel of the TONEOHM 550A. Plug the
other end into a wall outlet.
Connecting the Probes
Connect the Kelvin Probes supplied with the instrument into the Probe Socket.
Using the headphone socket
When the headphones are connected to this socket the internal speaker is switched off
and the tone switched to the headphones. Use only 3.5mm stereo jack plugs in this
socket. A stereo to mono adapter is required for use with an earpiece.
Selecting the range
Use the
Ω
, 200m
Ω
and 2
Ω
ranges to locate low resistance shorts. When locating faults
on heavier tracks, use the
Ω
range to gain more sensitivity and resolution. Use the
200
Ω
, 20K
Ω
ranges for general resistance measurements.
Summary of Contents for Toneohm 550A
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