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Chapter 3: Testing Performance

To verify threshold accuracy

High-to-Low Transitions

1 Set the DC Signal Source voltage to the "Initial V1 Setting" as shown in the table below.

The DC Signal Source voltage is referred to as "V1" throughout this procedure.

Table 1: Oscilloscope Threshold Voltage Setting and Initial V1 Setting

Note: In this test, complete steps 2, 3 and 4 for the first threshold voltage setting in the table

above. Then set the threshold voltage to the next value in the table and repeat steps 2, 3 and 4

for this threshold voltage setting. Finally, set the threshold voltage to the last value in the table

and repeat steps 2, 3 and 4 for the last threshold voltage setting.

Check the logic display at the bottom of the screen to ensure that all bits are logic 1.

If this is not the case, check the following:

• Read the DMM to determine if the input voltage is correctly set to the "Initial V1 Setting" value

shown in Table 1. Adjust the DC Signal Source voltage if necessary.

• Check the oscilloscope’s Digital set up to ensure that the logic threshold voltage is set to the

"Oscilloscope Threshold Voltage Setting" value shown in Table 1, and ensure that the display

of all bits is enabled.

• Ensure that the oscilloscope is in Run mode.

• Ensure that the oscilloscope trigger system is properly configured.

• If the oscilloscope is set up correctly and the input voltage is accurately set to the initial V1

setting and at least one bit is displayed as 0, then either the oscilloscope is out of calibration

or it is malfunctioning. If the oscilloscope has been powered on for at least 30 minutes, re-

calibrate the oscilloscope and retry this set up.

Perform the coarse threshold voltage search (to determine the measured threshold

voltage within ±50mV.) You will repeatedly adjust the voltage until all bits change from

logic 1 to logic 0. Record the voltage you applied just before all bits switched.

a Repeat the following steps until all displayed bits are logic 0:

• Reduce V1 by 50mV and examine the logic display.

• If all bits are 0, record the initial value of V1 (the value applied just before all bits

switched) as the V2 value in Table 2 and proceed to the Fine Threshold Voltage search.

• If at least one bit is still 1, reset the input voltage to the initial value of V1 shown in

Table 1. This is done so that when V1 is reduced, a significant voltage transition occurs.

• Reduce V1 by 100mV and examine the logic display.

• If all bits are 0, record the previous value of V1 (the value at which at least one logic bit

was still logic 1) as V2 in the table below. Proceed to the Fine Threshold Voltage search.

Oscilloscope Threshold Voltage Setting Initial V1 Setting

+5V 5.35V

0V 200mV

-5V -4.65V

1 2 ... 50 51 52 53 54 55 56 57 58 59 60 ... 161 162

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Agilent Technologies 8000 Series Spezifikationen Seite 55