Keithley 7999-2, Instruction Manual

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3-2 Operating Considerations
Introduction
This section contains information about operating considerations for the Model 7999-2
Three-Pole Multiplexer Card. The information is organized as follows:
• Maximum signal considerations
• Relay power and control
• Switching considerations
Maximum signal considerations
WARNING Maximum voltage between any conductor and ground is 42V.
CAUTION To prevent damage to the Model 7999-2, do not exceed the following maxi-
mum signal level specifications of the card:
• Maximum voltage: 30V DC, 42V peak
• Maximum current: 1A DC, switched
Relay power and control
To control relays, an ex24V DC voltage source must be connected to pin 5 of the
CONTROL/MEASURE/POWER connector. A channel is closed by setting the corresponding
control signal low. See Section 2 for complete connection information. Table 2-3 in Section 2
lists switched signals.
Switching considerations
Signals switched by the Model 7999-2 may be subject to various effects that can seriously
affect their integrity. The following paragraphs discuss these effects and ways to minimize
them.
Keeping connectors clean
As is the case with any high-resistance device, the integrity of connectors can be damaged if
they are not handled properly. If connector insulation becomes contaminated, the insulation
resistance will be substantially reduced, affecting high-impedance measurement paths.
Oils and salts from the skin can contaminate connector insulators, reducing their resistance.
Also, contaminants present in the air can be deposited on the insulator surface. To avoid these