Keithley 2657A-PM-200 User Manual page 12

Model 2657A-PM-200 Protection Module
Verify Model 2657A-PM-200 operation
A simplified block diagram of the Model 2657A-PM-200 is shown below.
Figure 8: Simplified diagram of the Model 2657A-PM-200
The voltage protection device is connected between Guard and LO. Low-leakage diodes are used to connect both
HI and Sense HI to the Guard terminal. This enables the protection module to protect a SMU connected to the IN
terminals from overvoltage.
The Zener diodes between LO and chassis and Sense LO and chassis limit the maximum voltage between LO and
chassis ground to 30 V to 40 V.
Use the following procedures to verify that the Model 2657A-PM-200 is operating properly.
12 PA-1055 Rev. A / February 2012