3 Calibration Procedures
64 Keysight 34980A Service Guide
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 and bank relays. Note that you cannot control the state of these relays
from the front panel but you can query the count.
– You can also query the state of the six relays on the internal DMM. These relays
open or close when a function or range is changed on a module.
– You can reset the count but the instrument must be unsecured (see
“Calibration Security” on page 35 to unsecure the instrument).
– The 34923A, 34924A, and 34933A modules can be configured for 2-wire
(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.
– The FET switches on the 34925A FET Multiplexer module have an infinite life
when 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.
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