Agilent 34970A/34972A Data Acquisition / Switch Unit
Agilent 34970A/34972A Data Acquisition / Switch Unit
Agilent 34970A/34972A Data Acquisition / Switch Unit
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Chapter 4 Calibration Procedures<br />
Relay Verification<br />
Relay Verification<br />
There are two methods you can use to verify relays:<br />
• Read the relay cycle count.<br />
• Measure the relay contact resistance.<br />
Relay Cycle Count<br />
The instrument has a Relay Maintenance System to help you predict<br />
relay end-of-life. The instrument counts the cycles on each relay in the<br />
instrument and stores the total count in non-volatile memory on each<br />
switch module. You can use this feature on any of the relay modules and<br />
the internal DMM.<br />
• In addition to the channel relays, you can also query the count on<br />
backplane relays and bank relays. Note that you cannot control the<br />
state of these relays from the front panel but you can query the count.<br />
• You can also query the state of the three relays on the internal DMM.<br />
These relays are numbered “1”, “2”, and “3” (which correspond to<br />
relays K102, K103, and K104 respectively). These relays open or close<br />
when a function or range is changed on a module.<br />
• The 34908A multiplexer contains 40 channels which are switched (HI<br />
only) using only 20 relays. Each relay is used to switch HI on two<br />
different channels (and only one channel can be closed at a time). The<br />
channels are arranged such that channels 01 and 21 use different<br />
contacts on the same relay. The remaining channels are also paired in<br />
the same manner (Channels 02 and 22, Channels 03 and 23, etc.).<br />
Therefore, when you query the relay count on a channel, the number<br />
reflects the number of times that the relay was closed. For example,<br />
the relay count will always be the same on Channels 01 and 21.<br />
• You can reset the count (allowed only from remote) but the<br />
instrument must be unsecured (see “To Unsecure for Calibration” on<br />
page 60 to unsecure the instrument).<br />
• For more information on relay life and load considerations, refer to<br />
“Relay Life and Preventative Maintenance” in Chapter 8 of the<br />
<strong>34970A</strong>/<strong>34972A</strong> User’s Guide.<br />
• A procedure to read the relay cycle count is given on page 65.<br />
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