Theory of Operation 5
Keysight 34970A/34972A Service Guide 153
34902A
Components in this discussion are located on the A1 circuit assembly
(34902-66501).
The control circuitry has two groupings of latches, relay drivers, and relays. The 16
voltage and resistance measurement channels are directly driven. Tree switching
controls the 2-wire/4-wire Ohms operation and connections to the analog bus.
The reed relays are non-latching and the relay driver and +5R is applied while a
channel is closed.