1236
Test Equipment
DCAE
Course Numbers 1236 and 3853
Avionics Technician
TEST EQUIPMENT MODULE
TRAINING USE ONLY
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ISSUE 1
1236
Test equipment
ELECTRICAL SAFETY
1.
Electricity can kill or main – directly or indirectly.
2.
Directly by the shock effect.
3.
Indirectly from smoke inhalation and burns from fires started by electricity.
4.
All electrical equipment (including ‘battery operated’) presents the hazards of electric
shock and electrical fire due to misuse or damage to the equipment.
5.
When high voltage supplies are used, the danger of LETHAL electrical shock must
be considered. Service regulations (1988) define potentially LETHAL voltages as
those in excess of:
a.
50 V ac (rms.)
b.
120 V dc
Thus, the domestic mains supply of 240 V ac is LETHAL. However, all voltages
must be considered dangerous.
6.
To reduce the risk/severity of electric shock or fire, the following precautions are
recommended:
a.
Examine the equipment and associated leads for damage before connecting to
the supply voltage.
b.
Remove or cover rings, bracelets, watches, medallions, etc.
c.
Have a tidy work area (no drinks, liquids, flammable waste, etc).
d.
When connecting/disconnecting test equipment leads (including the Fluke) do
so one lead at a time using one hand (the other hand in your pocket).
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Test Equipment
DIGITAL MULTIMETERS
INTRODUCTION
1.
The accuracy of readings obtained with single function meters is dependent
on the efficiency of the operator when interpreting the pointer position on the scale
plate. Digital multimeters remove this subjective element from readings, as you only
have to read off the illuminated digits on the display panel.
FLUKE 25
2.
This is a fully self-contained auto-ranging digital multimeter (see figure 1)
housed in a plastic storage case, and can be used in almost any environment in
which the mechanic is likely to encounter. It has the following features:
•
Carrying handle/stand
•
Four digit (max count 3200) Liquid Crystal Display (LCD)
•
10-function rotary selector switch
•
Manual/Auto range selector
•
Hold facility
•
Analog bar graph
•
Low battery warning
•
Range overload warning
•
Audible bleeper
•
Diode/continuity test facility
CARRYING HANDLE/STAND
3.
To enable the tilt bail to be used as a stand, pull the base out approximately
4" and rest the DMM on its end and the stand. To use it as a carrying handle, pull
the bail up approximately 1" and relocate the two bottom lugs into the alternate holes
provided.
DISPLAY PANEL
4.
This is a four digit LCD with a maximum count of 3200. Also displayed are
polarity and other various annunciators (indicators) for range selection, function
selection, battery indication etc. This display updates two times per second.
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Test equipment
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Test Equipment
Figure 1
ROTARY SELECTOR SWITCH
5.
The ten-function rotary selector switch selects the various functions, separate
selections required for ac and dc voltage and current ranges. On the Ohm’s range,
the common terminal is the negative terminal.
6.
As the rotary switch is moved from the OFF position, the meter performs a
brief self-check, culminating in all indications on the LCD panel being displayed.
7.
When the Fluke 25 DMM is in voltage mode the meter requires a high internal
impedance approximately 10M to ensure that the measurements taken are as
accurate as possible.
MANUAL/AUTO RANGE SELECTOR
8.
On initial range selection, the DMM is in the auto-ranging mode. Press the
range button (top left of the control panel) once to hold the minimum range, and
press repeatedly to step through, in ascending order, all possible ranges for that
particular function selected. To return to the auto-ranging mode once more, press
the range button and hold for 2 seconds. During range selection, auto or manual,
shunts or multipliers are selected as required to effect the range change.
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Test equipment
HOLD FACILITY
9.
There are two hold modes:
a.
Auto-Touch Hold. Press the hold button (top right corner of the
control panel) once, with the range selected, and the stable measurement will
be captured and displayed (except for readings around zero) only updating
when another stable measurement is taken - accompanied by an audible
bleep. This is useful when taking measurements in a difficult environment, as
the display can be read when convenient. To exit from the auto-touch hold
mode, press the Hold button for 2 seconds and release when an audible
bleep has been heard.
b.
Manual Touch Hold. Press and hold the Hold button whilst moving
the range selector switch from the OFF position to the desired range.
Release the hold button after 2 seconds and then press it again momentarily.
The display will now only be updated when the hold button is depressed
momentarily. To exit from the manual touch hold mode, press the hold button
for 2 seconds and an audible bleep will signify that the hold function has been
terminated. The corresponding annunciator on the display panel will also
disappear. To enter the auto-touch hold mode, the instrument must first be
switched off and then back on again, followed by the instructions in
sub-paragraph an above.
ANALOG BAR GRAPH DISPLAY
10.
The analog bar graph display shows, in a graphic form, the measurement
being taken and performs the same function as an analog needle, but it eliminates
the mechanical overshoot inherent in needle movements. Care must be exercised,
however, as the hold mode, whilst freezing the digital display, does not freeze the
bar graph display. Therefore, when using the hold facility, it is best to ignore the
indications provided by the bar graph. The display is updated 25 times per second.
11.
A negative (-) annunciator is displayed at the left end of the bar graph when
taking a reverse polarity dc measurement. Assume that a slowly varying dc voltage
is the input. As the input goes more +ve (from zero), a segment is displayed and
additional segments are displayed from left to right, to indicate that the input is
increasing. Now assume that the input is slowly decreasing. Fewer segments are
displayed and the -ve annunciator flashes as the input passes through zero. As the
input goes more -ve, the -ve annunciator stops flashing (remains on) and additional
segments are displayed from left to right, indicating a more -ve input. If the input is
equal to or exceeds the range selected, then the bar graph displays an arrow at the
far right of the display.
LOW BATTERY WARNING
12.
Each time the function switch is moved to a new position, battery voltage is
tested. Under normal usage, the battery life should be in excess of 1000 hours.
When the low battery indicator is displayed on the LCD panel, it indicates that less
than 60 hours life remains in the battery and that it should be changed.
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Test Equipment
RANGE OVERLOAD WARNING
13.
Range overload warning is indicated by ‘OL’ being displayed. This is caused
by the input exceeding the particular range selected. Refer to the range table in the
handbook for the maximum inputs for the particular range selected.
AUDIBLE BLEEPER
14.
The audible bleeper sounds when either the range button or the hold button is
depressed, or when using the diode/continuity test function (see below).
DIODE/CONTINUITY TEST FACILITY
15.
The diode/test facility measures the voltage dropped across the test
component utilising a calibrated current produced by the DMM. Developed voltages
in excess of 2.08 V result in an overload indication. As the voltage developed falls
below 0.7 V (corresponding to a resistance of approximately 1000 ohms) a single
bleep is emitted, and if the voltage falls below 0.1 V (corresponding to a resistance of
approximately 150 ohms) a continuous tone is emitted. The LCD panel indicates
voltage drop (in volts) and not ohms.
16.
Audible continuity testing is also performed in this mode. A continuous tone
sounds for test resistances below approximately 150 ohms. An intermittent
connection produces erratic beeps, and can be a valuable troubleshooting aid. Test
resistances from approximately 150 ohms to 1000 ohms produce a short tone similar
to a forward biased diode. Test resistances less than 20 Kilo-ohms will produce an
on-scale reading.
CONDUCTANCE MODE
17.
Conductance measurement is performed with the function selector switch in
the ohms function. The conductance range can only be entered using manual range
selection; auto-range cannot enter the conductance range. The conductance range
can be used to measure conductance (1/ohms, the inverse of resistance) or to
measure very high resistances (greater than 32 Mohms).
18.
Conductance measurements are displayed in nanosiemens (nS). Calculate
mega-ohms by dividing 1000 by the number of nanosiemens displayed.
Example: 2 nS = 1000  2 = 500 Mohms.
PRE-USE CHECKS
19.
a.
Labels. Check that the calibration certificate and the routine service
labels are in date.
b.
Cables. Ensure that there is no physical damage to the supply or test
leads.
c.
Case. Ensure there is no physical damage to the instrument.
d.
Face. Ensure that the display is not damaged and that all the controls
are free to operate in a positive manner.
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Test equipment
e.
Extras: (1)
Examine all accessories and leads for signs of damage, fraying,
cracks or splits.
(2)
Check the leads using the ohms range.
(3)
Check the fuses in accordance with paragraph 23.
WARNING
TO AVOID ELECTRICAL SHOCK OR DAMAGE TO THE METER, DO NOT
APPLY MORE THAN 1000V BETWEEN ANY TERMINAL AND
EARTH/GROUND.
WARNING
INSTRUMENT DAMAGE AND OPERATOR INJURY MAY RESULT IF THE
FUSE BLOWS WHILE CURRENT IS BEING MEASURED IN A CIRCUIT
WHICH EXHIBITS AN OPEN CIRCUIT VOLTAGE GREATER THAN 600V.
DO NOT ATTEMPT AN IN-CIRCUIT CURRENT MEASUREMENT WHERE
THE POTENTIAL IS GREATER THAN 600V.
Caution
During resistance measurement turn test circuit power off and discharge
all capacitors before attempting in-circuit resistance measurements.
METER CONNECTION
Table 1 shows input terminals and limits for connection of this meter.
FUNCTION
Black Lead
MIN DISPLAY
READING
MAX DISPLAY
READING
MAXIMUM
INPUT
1000V
1000V
INPUT TERMINALS
Red Lead
V
V
V
COM
0.001V
mV
mV
V
COM
0.1 mV
320.0 mV
V
COM
COM
0.1
0.01 nS
32.00 M
32.00 nS
V
COM
0.001V
2.08V
COM
0.01A
COM
0.01 mA
320.0 mA
320mA 600V
COM
0.1 A
3200 A
320mA 600V

(nS)
A
mA/A
mA/A
mA
A
A
A
mA
A
500V
10A*
600V
7252/24
20.
* 10 A CONTINUOUS
Table 1
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Test Equipment
BATTERY REMOVAL AND REPLACEMENT
21.
The DMM uses one PP3 type battery. To gain access, ensure that the rotary
selector switch is in the off position and remove the test leads. Turn the instrument
over and remove the four cross-point screws located under the stand. Pull the
battery cover/holder out and disconnect and remove the battery. Fitting is the
reverse of removal. Care must be taken to ensure that the battery leads are located
in the slots provided in the holder prior to fitment as damage to these leads could
otherwise occur.
FUSES
22.
Three fuses are provided, all of the fast blow type; 630 mA, 3 A and 15 A.
These are located in the battery compartment, access being identical to that of
battery replacement (see above).
23.
Testing of these fuses are carried out as follows:
a.
To test the 15 A fuse (which protects the Amps range) connect a test
lead to the V terminal and connect the other end the A terminal. Select the
Ohms range and an indication of 0.0 - 0.3  indicates a serviceable fuse.
b.
To test the 3 A and 630 mA fuses (which protect the milliamps and
microamps ranges respectively), connect a test lead to the V terminal and
connect the other end to the mA/µA terminal. Select the Ohms range and an
indication of 5.3 - 6.0  indicates both fuses are serviceable. A ruptured fuse
will result in an overload reading.
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Test equipment
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Test Equipment
INSULATION AND CONTINUITY TESTERS
INTRODUCTION
1.
Introduction testing may be divided into two basic categories, testing of
components and testing of cables. In both cases the principle is the same. The
insulation is subjected to a higher than normal voltage, whilst at the same time its
resistance is measured. This test voltage is at least twice the normal working
voltage of the circuit under test. The test is carried out using the high voltage, to try
to pass a current where normally no significant current would flow. If the voltage
used to supply the current is known, then by simple application of Ohm’s Law, the
resistance of the insulation may be calculated. For example:
R
V
I
Where the voltage applied is 200 volts and current is measured at 0.0001 amps:
R=
200
 2 Mohms
0.0001
2.
Thus the resistance of the circuit being tested is 2 M. In practice, the
insulation tester will produce a known voltage at the test lead terminals, this is then
used to try to pass current through an insulator, ie, and the insulation resistance is
high. The instrument will have a dial calibrated in kilohms or megohms, and thus a
direct reading of insulation resistance may be made.
SAFETY PRECAUTIONS
3.
Because high voltages are employed to stress the insulation, it is important
that insulation tests are carried out in the approved manner, and only when an
approved maintenance schedule is being used or with the authority of a suitably
qualified engineering officer. In particular, insulation tests are never to be carried out
on circuits containing electro-explosive devices (EED), also, because most
semiconductors are damaged by high voltages, circuits or components containing
these devices are not subject to high voltage insulation tests.
4.
Although the voltage employed in the instrument (250 V dc – 1000 V dc) is
high there is normally no risk of injury while in use as the current is limited, due to the
way the instrument is designed.
5.
Safety Precautions to prevent injury
a.
Ensure that a pre-use check has been carried out on the tester.
b.
If possible, avoid carrying out insulation tests on damp equipment or in
damp conditions.
c.
Ensure no EEDs are fitted to the circuit to be tested.
d.
Disconnect capacitors, if practicable, or ensure that they are
discharged after testing.
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6.
Test equipment
Safety Precautions to prevent damage
a.
Ensure that testing is carried out in accordance with an authorized
procedure.
b.
Ensure that the correct test voltage is being applied.
c.
Never connect an insulation tester to a live circuit.
d.
Avoid using a tester in the presence of strong magnetic fields.
e.
Never test circuits containing semiconductor devices.
Figure 1 – Robin KMP 3075DL Insulation/Continuity Tester
DESCRIPTION
7.
The tester (see figure 1) is a compact high specification digital continuity and
insulation tester. The case uses themomory plastics to give an enhanced look as
well as durability. The design of the case is such that it is an integral part of the unit.
The instrument is protected in transit by its own integral lid. Microprocessor
technology provides advanced functionality and maximizes the user-friendly aspects.
In the past digital insulation testers have been removed for the excessive scatter of
digits as capacitive circuits are charging, ie, digital flicker. The effects have been
eliminated with this unit.
•
Display panel
•
Rotary selector switches
•
‘TracLoc’ selector switch
•
Back light button
•
Press-to-test button
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Test Equipment
•
Analogue bar graph displaying applied voltage
•
Low battery warning
•
Out of Range (OR) warning
•
Live circuit warning indicator including audio alert
•
Auto null
•
Accessories
8.
Display Panel. This is a four-digit display with a maximum insulation
resistance (IR) reading of 0-2000 M also in IR mode an analogue display bar is
shown to give a reading of the applied voltage of the test. When selected to
Continuity mode the display reads up to 2000 .
9.
Rotary Selector Switches. The two rotary switches are similar in style but
carry out separate tasks switch 1 provides an off position, voltage applied in
insulation testing mode and an all-purpose ohms reading position plus an auto null
position. Rotary switch 2 is the range position switch red numbers for insulation and
green for continuity.
10.
‘TracLoc’ Switch. An additional feature of this unit is a function called
‘TracLoc’. This enables the unit, when in Loc mode, to maintain a display of the
reading after the test source voltage has been removed, and a continuous
assessment of the circuit when selected to Trac Mode.
11.
Backlight Button. A backlight for the display is provided in low light
conditions.
12.
Press to Test Button. Press to carry out a test, additionally if a continuous
test is to be carried out the button can be twisted and will remain in the test condition
until it is pressed again.
13.
Analogue Bar Graph. Displays the applied voltage while the circuit is under
insulation testing.
14.
Low Battery Warning. Is displayed when the internal battery is not holding
enough charge as to continue the test. The batteries are housed inside the panel
underneath the unit. Six AA cells are required to power the unit.
15.
Out of Range Warning (OR). This is displayed whenever the circuit under test
cannot be measured within the selected range. The range should be moved up to a
greater one and tested again.
16.
Live Circuit Warning Indicator. Insulation testing should never be carried out
on circuits that have power still applied, to warn the operator of a live circuit a static
flash symbol will be illuminated on the display there is also a low audible buzzer which
will sound while the warning sign flashes. If this symbol is displayed, testing should
cease immediately.
17.
Auto Null. This function allows for the test leads resistance values to be
removed from the final reading on the display when undertaking continuity testing.
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Test equipment
Connect the test leads to the instrument and switch to the Auto Null and 20 
continuity range. Short the leads out and return to the  selection.
18.
Accessories. The kit will also come with a bag set comprising two sets of
test leads. Set one is a short set and Set two a much longer set of leads.
PRE-USE CHECKS
19.
a.
Labels. Check that the calibration certificate and the routine service
labels are in date.
b.
Cables. Ensure that there is no physical damage to the supply or test
leads.
c.
Case. Ensure there is no physical damage to the instrument.
d.
Face. Ensure that the display is not damaged and that all the controls
are free to operate in a positive manner.
e.
Extras. Ensure battery is serviceable.
OPERATION
20.
Insulation resistance testing as with continuity testing has no hard or fast rules
that can be laid down to cover every eventuality. However, there are certain basic
rules, which must be followed whenever insulation testing is to be undertaken.
These are as follows:
a.
Isolate the circuit to be tested from the power supply.
b.
Remove the circuit fuses or trip circuit breakers and fit appropriate
dummy servicing devices.
c.
Disconnect all earth connections. Disconnecting at the earth terminal
block(s) will normally do this. Do not disconnect at the earth stud.
d.
Short circuit any normally open relay contacts.
e.
Any capacitor in the circuit should be disconnected before commencing
the test.
LETHAL WARNING
IF CAPACITORS HAVE BEEN CHARGED UP DURING THE
TESTING PROCESS, THEY MUST BE DISCHARGED
IMMEDIATELY THE TEST IS CONCLUDED.
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Test Equipment
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Test equipment
Safety Ohmmeter 1681
INTRODUCTION
1. The safety ohmmeter 1681 is a hand held tester that can be used to measure
resistance values between 1 milliohm and 20,000 ohms.
2. The instrument enables measurement of low resistance of electrical bonds
and wiring in electrical installations, contact resistance of circuit breakers and
switches, the resistance of bus bar joints, fuses etc.
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Test Equipment
SAFETY PRECAUTIONS
3. This tester may be used by suitably trained personnel in potentially explosive
atmospheres. It must not be connected to any other powered source.
4. To avoid any possibility of electric shock do not use the tester on live
installations. If in doubt, check for the presence of high voltages with suitable test
equipment against a known “good” earth prior to any resistance measurement
being made.
DESCRIPTION
5.
The safety ohmmeter is a portable, battery powered tester. It is comes in its
own carrying case, which also houses the array of test leads provided. The
tester is used from within the case and the front panel incorporates a range
selector switch, a liquid crystal display incorporating a battery condition
annunciator. an on button and a backlight switch. The test leads also plug
into the unit on this panel and there is access to the zero adjustment screw.
6. The safety ohmmeter testing is carried out using the four wire test this
technique would highlight the following common faults:







Individual strands of wire broken
Squashed wires
Wrong gauge wire fitted
Dirty connections
Poor crimp connections
Dry solder joints
Poorly mating connectors
When measuring low resistance measurements using the four-wire technique the
test lead or test interface wiring will be automatically nulled out.
PRE-USE CHECKS
7.
a.
Labels. Check that the calibration certificate and the routine service
labels are in date.
b.
Cables. Ensure that there is no physical damage to the test leads.
c.
Case. Ensure there is no physical damage to the instrument.
d.
Face. Ensure that the display is not damaged and that all the controls
are free to operate in a positive manner.
e.
Extras. Ensure battery is serviceable.
OPERATION
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8.
Test equipment
To avoid any possibility of electric shock, do not use tester on live
installations.
a. Switch the Tester ON
b. Connect one test lead to one side of the bond to be tested, making
sure that a clean, reliable connection is made.
c. Apply the second test lead to the other side of the bond to be tested.
d. Note the bond resistance indicated and verify that the resistance is
within required limits.
OFFSET CONTROL AND EXTENSION LEADS
9.
In normal use, no pre-calibration or pre-setting of the zero is necessary.
Accurate measurements can be made with all of the test leads supplied up
to and including the 5-meter lead. The OFFSET control is provided to
compensate for offsets introduced during testing when long extension
leads or probe adaptors are used. In normal use the zero control is set to
counter clockwise, when using extensions over 5 meters connect the ends
together and adjust the screw clockwise to give a zero indication on the
display.
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Test Equipment
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Test equipment
TIME DOMAIN REFLECTOMETER
INTRODUCTION
1. The Time Domain Reflectometer (TDR) is a pulse reflection Cable Test set, for
locating cable faults and evaluating changes in impedance caused by
connectors, taps, terminations etc. Pulses transmitted into a cable are reflected
by cable imperfections. The transmitted pulse and the reflected pulse(s) are
shown on the display. The time taken by the pulse to travel to the fault and return
is a measure of the distance to the fault. Distance to fault is displayed on the
screen after the cursor is positioned to coincide with the start of the fault pulse.
The type of fault can be determined by analysis of the displayed waveform.
2. The TDR test set was designed principally for 50, 75 and 93 coaxial cables it is
equally effective on other cables types as a fault locator. Impedance mismatches
can be measured in terms of Return Loss (dBRL) with the location displayed in
feet, meters or time.
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Test Equipment
DISCRIPTION
3. The TDR Model T631 comprises off the unit, carry bag, AC Adaptor,
rechargeable batteries (8) user guide and test leads
4. The TDR Model T631 has the facility to store up to 15 traces with the ability to
transfer to a printer or PC; it also has dual cursors for point-to-point
measurements.
5. The test set can be power by its own internal rechargeable batteries or by the
mains adaptor. The fully charged batteries will give up to 8 hours operation and
the test set will automatically switch off before the batteries are fully discharged.
6. The test set has a LCD display panel, with backlight (will auto switch off after 5
mins). The 24 press buttons give the operator access to all functions of the test
set, some buttons have dual operation.
7. A BNC socket allows connection via test lead to cable under test. A 9 way D
connector give interface connection to printer or PC.
8. The AC adaptor connects into the side via jack socket and access to the
rechargeable batteries is from the rear.
PRE-USE CHECKS
9.
a.
Labels. Check that the calibration certificate and the routine service
labels are in date.
b.
Cables. Ensure that there is no physical damage to the test leads.
c.
Case. Ensure there is no physical damage to the instrument.
d.
Face. Ensure that the display is not damaged and that all the controls
are free to operate in a positive manner.
e.
Extras. Ensure the AC Adaptor if required is serviceable.
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Test equipment
SAMPLE TRACES
10. Open circuit/high impedance series faults
Note: Positive (upward) reflection
Reflected Pulse
Transmit Pulse
11. Short circuit/low impedance shunt faults
Note: Negative (downward) reflection
Reflected Pulse
Transmit Pulse
12. Inline connection and Aerial Termination
Joint gives ‘S’ shaped reflection
Transmit Pulse
Reflected Pulse Aerial
(Reflection could be positive
dependent on aerial type)
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Test Equipment
OPERATION
13. The unit has 4 display modes
a.
b.
c.
d.
A ‘live’ trace
A stored trace recalled from memory
A live and stored trace together for comparison
The difference between a live and stored trace
These can be selected using the ‘Mode’ button on the front control panel
14. For correct operation the cable under test should be taken out of service with all
sources of supply removed. Any RF signals present on the cables may corrupt
the display.
15. Power the unit from previously charged internal batteries or from the AC adaptor.
Press the ON button and the display should appear, rotate the contrast control to
obtain a well-defined trace.
16. The display will be similar to Fig 1 below
1.703m
2ns
50
LINE
6m
A1
p667
Figure 1
17. The TDR on initial switch on will be in the ‘Live’ trace mode, on the 6m range, a
propagation velocity factor of 0.667 and impedance of 50. The left hand cursor,
(dotted), will be at the start of the transmitted pulse (0m) and the right hand
cursor, (solid); will be approximately one third across the display (1.703m).
18. The distance units, impedance and propagation velocity factor mode can be reprogrammed via the ‘HELP’ (?) button.
19. Connect the cable under test directly to the BNC socket or via test lead supplied.
Move the left hand cursor to the end of the test lead if used; this removes the
length of the test lead from the distance reading.
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Test equipment
20. The TDR can be used to locate the cable fault using the unit in manual mode.
Full description of the operational procedures for the manual mode can be found
in the operating manual.
21. This TDR can automatically scan a cable and locate the nearest significant
feature and configure the parameters of the unit to optimally display the feature.
To ensure the best possible benefit is achieved in this mode of operation, the left
and right hand cursors must be placed at the point that the cable under test is
connected to the TDR. This will start the scan at the correct point and not include
any test lead connected.
22. Once the cable under test is connected and the cursors set to the correct point,
the operator can press the ‘FIND FAULT’ button to start the automatic sequence.
Pressing the button a second or subsequent time locates the next significant
feature alone the cable.
23. This automatic feature is intended for use on co-axial cables where the reflection
from a fault may be quite small, so the sensitivity used is quite high. On a power
cable or twisted pair, mismatches due to joints, or change of cable type may give
rise to many reflections, which the instrument will detect even though they are not
faults.
24. To save the live trace to memory, press the ‘SAVE’ button and select the required
storage location, note any trace already in the selected location will be
overwritten.
25. To recall a saved trace press the ‘RECALL’ button and select the location as
required. The TDR display will now show the recalled trace and the location it is
held in i.e. M1
26. To compare a live trace against a stored one, press the ‘MODE’ button and select
option 3 (live & memory). The traces are overlaid on one another, but they can be
separated by use of the ‘SHIFT’ buttons. To use the difference between live and
memory, select option 4 from the mode selection.
27. The TDR has an internal help section available when the ‘?’ button is selected.
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