Tracker-2800-2800S.pdf - 第14页
14 2-4 Alternate Mode The Alternate (ALT) mode of the Tr acker 2800 is provided to automatically switch b ack and forth between Channel A and Channel B. This allo ws easy comparison between two devices or the same points…
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2-3. Channel Selection
There are two channels on the Tracker 2800 (channel A and channel B) which are selected by pressing
the appropriate front panel button. When using a single channel, the red probe should be plugged into
the corresponding channel test terminal and the black probe or common test lead should be plugged
into the common test terminal. When testing, the red probe should be connected to the positive
terminal of a device (i.e. anode, +V, etc.) and the black probe should be connected to the negative
terminal of a device or a common reference (i.e. cathode, ground). Following this procedure should
assure that the signature appears in the correct quadrants of the LCD display.
Figure 2-3
Manual probing of
components on a printed
circuit board is accomplished
using hand held probes
connected to the Tracker 2800
front panel.
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2-4 Alternate Mode
The Alternate (ALT) mode of the Tracker 2800 is provided to automatically switch back and forth
between Channel A and Channel B. This allows easy comparison between two devices or the same
points on two circuit boards. The Alternate mode is selected by pressing the ALT button on the front
panel. The alternation frequency is varied by pressing the RATE control button on the Tracker LCD
then pressing the and buttons until the desired alternation frequency is reached. The RATE is
numbered from 1 (fastest) to 10 (slowest). Press the RATE button to return to the power-up menu.
Figure 2-4 shows how the instrument is connected to a known good board and a board under test. This
test mode uses the supplied common test leads to connect two equivalent points on the boards to the
common test terminal. Note that the black probe is plugged into the channel B test terminal.
When using ALT mode, a green check mark or red “X” on the bottom right portion of the LCD will
indicate a pass or fail comparison.
Figure 2-4
Channel A and B
with the ALT mode
can be used to make
direct comparisons
of two PCBs.
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To set the allowed maximum deviation or “Tolerance” when comparing the A channel versus the B
channel select the MENU front panel button to display the Main menu on the LCD (left image in
figure 2-6). Press the SCAN button on the LCD to display the Scan menu (middle image in figure 2-6).
Press TOL to display the Tolerance menu (right image in figure 2-6). Use the and arrow buttons
to adjust the tolerance allowed during comparison. It is adjustable from 0 to 90.
Figure 2-6. Selecting tolerance setting used during A vs. B comparison
2-5 Resistance Selection
The Tracker 2800 is designed with nine resistance ranges (10, 50 100, 500, 1k, 5k, 10k,
50k and 100k). A resistance range is selected by pressing the appropriate button on the front panel.
Each button has a dual function. For example, pressing the 100 button (steady LED indication)
selects 100 as the resistance value. Pressing it again (blinking LED indication) selects 500 as the
resistance value. It is best to start with one of the middle resistance values (i.e. 100 or 1k). If the
signature on the LCD display is close to an open (horizontal trace) select the next higher resistance for
a more descriptive signature. If the signature is close to a short (vertical trace), go the next lower
resistance. An optimum resistive signature is approximately at a 45° angle to the horizontal and
vertical lines of the graticule.
The SCAN feature will allow for sequencing through the resistance ranges at a speed set by the RATE
selected. This feature allows the user to see the signature of a component in different resistance ranges
while keeping their hands free to hold the test leads.
Figure 2-5
LCD displays
indicating a pass
A/B comparison
(green check mark –
left image) and fail
A/B comparison (red
X – right image).
Press the SCAN button Press the TOL button Use and to select the Tolerance