Keysight 34921A-34925A User’s Guide 89
The overcurrent protection devices will be rated, or the snubber circuits will limit the current, according to:
1. Peak voltage, channel-to-channel or channel-to-earth.
2. With input resistors bypassed. Bypassing resistors will reduce the lifetime of relays. See the rated load relay life characteristics.
3. With input protection resistors: 2 x 100
±5%; 0.5W; TC = ±200 ppm/°C. The series resistance of the 34923/24 limits the use of the 100
range.
5. Limited to 6 W of channel resistance power loss per module.
6. Into analog bus. System errors are included in the internal DMM measurement accuracy specifications.
7. Channel resistance is typically < 1.5
but can go as high as 50 when a channel is used in measurement applications with < 10 mA load
current. Increased relay channel resistance for measurements with load currents below 10 mA can occur on cards that have been out of
service or following relay inactivity for periods of greater than 1 week. Switching relays for 2K cycles prior to use may reduce the variation in
channel resistance. Keysight recommends the use of 4-wire Ohms for resistance measurements. For high accuracy voltage measurements,
select the DMM input resistance setting of >10 G ohms to minimize the impact of relay contact resistance.
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