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Chapter 4: Testing Performance

To test input impedance

This test checks the input impedance of the vertical inputs. A four-wire measurement is used to

accurately measure the 50  and 1 M inputs.

Specification: 1 M±1% and 50 ±2.5%

Equipment Required

Procedure

Set up the multimeter to make a four-wire resistance measurement.

2 Assemble the test cables.

a Use the two BNC-to-banana adapters to connect one end of each BNC cable to the four-wire

resistance connections on the multimeter.

b Connect the free ends of the cables to the BNC tee.

See Figure 4-1.

Figure 4-1

Input Resistance Equipment Setup

3 Connect the male end of the BNC tee to the channel 1 input of the oscilloscope.

4 Press Default Setup to set the oscilloscope to default conditions. Then set the sensitivity for

Channel 1 to 5 mV/div.

5 Open the Channel Setup dialog box for Channel 1 (Setup > Channel 1) to set the channel input

resistance to 50  and verify a resistance reading of 50

 ±1.25 .

6 Record the readings in the Performance Test Record at the end of this chapter (Impedance Test

table).

7 Repeat steps 5 and 6 for the remaining 50 vertical sensitivities in the Impedance Test table

located at the end of this chapter.

8 Repeat steps 3 through 7 on the remaining channels of the oscilloscope.

9 Repeat steps 3 through 8 using an input resistance of 1 M instead of 50  and verify resistance

readings of 1 M

 ±10 k.

Equipment Critical Specifications Recommended Model/Part

Digital Multimeter Measure resistance (4-wire) at better than

±0.1% accuracy

Agilent 34401A

Cables (2) BNC Agilent 10503A

Adapter BNC Tee (m)(f)(f) Agilent 1250-0781

Adapters (2) BNC (f) to dual banana (m) Agilent 1251-2277

To ohmmeter

4-wire inputs

To oscilloscope

channel input

1 2 ... 46 47 48 49 50 51 52 53 54 55 56 ... 165 166

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Agilent Technologies Ininiium 9000 Dokumentacja Strona 51