B. Operating Performance Checks
Position a cursor at the most far left position.
The absolute distance measurement for the cursor is the lower limit for cursor readout range.
This number should be less than -1 ft. (-0.3 m).
B.4.13
Cursor Readout Resolution Check
1. Use the
HORIZONTAL SCALE
knob to set the horizontal scale to 0.00330 ft./div or
0.001 m/div.
2. Position a cursor on the screen and note the absolute distance measurement for the cursor.
3. Move the cursor the smallest possible step using the
HORIZONTAL POSITION
knob.
The difference between the new distance measurement and the previous is the minimum
cursor readout resolution.
B.4.14
Distance Measurement Accuracy Check
Accuracy is determined by taking a cable of known length and velocity and comparing the
known values against measured values. Accuracy is reported as a percentage. When determining
accuracy, ensure that horizontal calibration has been performed accurately.
Accuracy should be checked for Short, Medium, and Long settings.
B.4.15
Ohm Readout Range Check
1. Connect the 36 in. reference cable to the CT100B.
2. Position a cursor on the trace well beyond the end of the cable. The vertical impedance
measurement should read
≥
1.5k ohms.
3. Position a cursor on the trace well before the leading edge of the pulse. The vertical
impedance measurement should read
≤
1 ohm.
B.4.16
Resolution Check
Position a cursor at a point of the trace where the vertical impedance measurement is greater
than 1 ohm and less than 1500 ohms. The CT100B should display 3 digits for this
measurement.
B.4.17
Vertical Accuracy Check (ohms)
1. Vertical accuracy is checked by comparing CT100B impedance measurements against a
load of known impedance. The supplied 50 ohm terminator is required.
2. Within the
Main
→
Settings
→
Display
submenu, select the
Ohms Rho
button until
Ohms
is marked with asterisks. An ohms at cursor reading now appears on the right side of the
screen.
3. Connect a 50 ohm terminator onto the front panel cable connector.
4. Move a cursor out to a length greater than 300 ns. Impedance may change a small amount
from point to point.
5. Average impedance amongst a number of points along the trace determines vertical
accuracy. Impedance at cursor should be between 45 and 55 ohms.
6. Vertical accuracy should be checked for Short, Medium, and Long cable lengths.
CT100B TDR Cable Analyzers Operator’s Manual
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