Relay Plug-In Modules - Agilent Technologies 34980A Service Manual

Relay Plug-in Modules

There are two methods you can use to verify relays:
• Read the relay cycle count.
• Measure the relay contact resistance.
Relay Cycle Count
The instrument has a Relay Maintenance System to 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
• You can also query the state of the six relays on the internal DMM. These relays open
• You can reset the count but the instrument must be unsecured (see
• The 34923A, 34924A, and 34933A modules can be configured for 2-wire
• The FET switches on the 34925A FET Multiplexer module have an infinite life when
• On the RF Multiplexer modules (34941A, 34942A), the signal path to the COM
34980A Service Guide
and bank relays. Note that you cannot control the state of these relays from the front
panel but you can query the count.
or close when a function or range is changed on a module.
Security" on page 49 to unsecure the instrument).
(differential) or 1-wire (single ended) measurements. Since two coils are required to
drive each channel relay in the 2-wire mode, the module stores the cycle count for
each coil and returns the greater of the two. To determine the cycle count for each
coil, reconfigure the module for the 1-wire mode (a power cycle is required) and
query the count.
used under normal operating conditions. Therefore, the cycle count is not recorded
and this command always returns "0" (will not generate an error). Although the count
on the FET switches is not recorded, you can read the actual cycle count on the
mechanical Analog Bus relays.
terminal consists of both a channel relay and a bank relay. For each bank, the module
stores the cycle count for each channel relay, the bank relay, and returns the greater of
the two. For example, to determine the cycle count on Channel 11, the module recalls
the count on Channel 11, the count on the Bank 1 relay, and returns the greater of the
two. In addition, the cycle count on the two channels within the same physical relay
package, will always be equal. Therefore, the cycle count for Channels 11 and 12 will
always be equal.
Calibration Procedures
"Calibration
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