Keithley 7038, Instruction Manual

Servicing

4-2

4.3.2 Recommended verification equipment

Table 4-1 summarizes the test equipment recommended for
performance verification. Alternate equipment may be used
as long as the corresponding specifications are at least as
good as those listed.

4.3.3 Insertion loss tests

Insertion loss tests are performed by applying a 10MHz-
2GHz signal from a 75

Ω

 network analyzer to the Model

7038 channel inputs and then measuring the amount of atten-
uation as the signal passes through the card.

Proceed as follows:

1. Set the network analyzer to sweep the 10MHz to 2GHz

frequency range.

2. Normalize the analyzer reference channel to 0dB on the

display.

3. Connect the network analyzer to the Model 7038 as

shown in Figure 4-1. Be sure to use 75

Ω

 cables for all

insertion loss tests.

4. Install the Model 7038 in the Model 7001 or 7002 main-

frame.

5. Close channel 1 on the Model 7038 card.
6. Verify that the insertion loss values are within the limits

shown in Table 4-2.

7. Open the closed channel.
8. Repeat steps 3 through 7 for channels 2 through 12. For

each channel:

• Connect the analyzer signal to the input jack of the

channel being tested.

• Be sure the signal output cable is connected to the cor-

rect output jack.

• Close only the channel being tested.

• Verify that the insertion loss values at the various fre-

quencies are within the limits stated in Table 4-2.

4.3.4 Isolation resistance tests

These tests check the isolation resistance between various
Model 7038 terminals using the ohms function of a Model
6517A Electrometer.

CAUTION

The following tests use the Model 6517A
voltage source to measure resistance. Do
not apply more than 24V to the Model
7038 to avoid card damage.

4.3.5 Channel isolation tests

Perform the following steps to check channel isolation:

1. Connect the Model 6517A Electrometer to the center

conductors of channels 1 and 2, as shown in Figure 4-2.

2. With the power off, install the Model 7038 card in the

mainframe.

3. Turn on the mainframe and the Model 6517A power,

and allow the electrometer to warm up for at least one
hour before making measurements. Make sure the volt-
age source is turned off. 

Table 4-2

Insertion loss values

Frequency

Insertion loss

10MHz

<0.25dB

100MHz

<0.5dB

500MHz

<1.0dB

900MHz

<1.5dB

2GHz

<3.0dB

Table 4-1

Recommended verification equipment

Description

Manufacturer and Model Specifications

Test

Network Analyzer Hewlett Packard 8713C

(Option 1EC, 75

Ω

)

10MHz–2GHz

Insertion loss

Electrometer

Keithley 6517A

100M

Ω

, ±0.151%

1G

Ω

, ±0.226%

Isolation