HP 34970A manual System-Related Operations

Chapter 4 Features and Functions

System-Related Operations

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The instrument has a ext”x fxto help you predict relay end-of-life. The instrument counts the cycles on each relay in the instrument and stores the total count in non-volatile memory on each switch module. You can use this feature on any of the relay modules and the internal DMM.

∙In addition to the channel relays, you can also query the count on backplane relays and bank relays. Note that you cannot control the state of these relays from the front panel but you can query the count. For more information on channel numbering and layout, refer to “Module Overview” starting on page 163.

∙You can also query the state of the three relays on the internal DMM. These relays are numbered “1”, “2”, and “3”. These relays open or close when a function or range is changed on a module.

∙ The HP 34908A multiplexer contains 40 channels which are switched 4

(HI only) using only 20 relays. Each relay is used to switch HI on two different channels (and only one channel can be closed at a time). The channels are arranged such that channels 01 and 21 use different contacts on the same relay. The remaining channels are also paired in the same manner (channels 02 and 22, channels 03 and 23, etc.). Therefore, when you query the relay count on a channel, the number reflects the number of times that the relay was closed. For example, the relay count will always be the same on channels 01 and 21.

∙You can reset the count (allowed only from remote) but the instrument must be unsecured (see “Calibration Overview” on page 155 to unsecure the instrument).

∙For more information on relay life and load considerations, refer to “Relay Life and Preventative Maintenance” starting on page 399.

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