Hi sma,
1. From your post, it sounds like you want to separate the measurements into 2-wire and 4-wire configurations. In addition, you want to use the PXI-2527's 2-Wire 32x1 Multiplexer Topology instead of its Independent Topology. You can do this, but you need to control a configuration relay (KBC01) when moving back and forth between 2- and 4-wire measurements. You would control the configuration relay using the Relay API of NI-SWITCH or DAQmx Switch.
The Relay API of NI-SWITCH includes niSwitch Relay Control, Get Relay Position, and Get Relay Count VIs (or functions). The Relay API of DAQmx Switch includes DAQmx Switch Open Relays, Close Relays, Get Relay Count, and Get Relay Position VIs (or functions).
Looking at the Independent Topology of the PXI-2527, you must organize your signal connections in an appropriate manner to be able to use both 2-wire and 4-wire configurations. One such method is to have your 2-wire measurements using ch0-12 and ch16-28 (26 channels total), ch13 and ch29 as your first 4-wire measurement, and ch14 and ch30 as your second 4-wire measurement. The reason you must separate the 2-wire signals is because you want to have channels available on both sides of the KBC01 configuration relay for the 4-wire signals.
When you configure the PXI-2527 in its 2-Wire 32x1 Multiplexer Topology, the KBC01 configuration relay is closed. Upon connecting a 2-wire measurement, CHX +/- are connected to COM0 +/- (where X is any number from 0 to 31). This is shown in 2wire.jpg, attached to this post in Pics.zip.
Upon connecting a 4-wire measurement, you will want to open the KBC01 configuration relay, because CHX +/- are connected to COM0 +/-and CHY +/- are connected to COM1+/- (where X is any number from 0 to 15, and Y is any number from 16 to 31). This is shown in 4wire.jpg. If you forget to open the KBC01 configuration relay, your V+ and Sense+ will be shorted together (and your V- and Sense- will also be shorted together). This is undesired, as V+ and Sense+ should be connected together at your load, not within the switch.
Lastly, remember to close KBC01 before connecting another 2-wire measurement.
Because you have to individually control the configuration relay, you will no longer be able to scan the PXI-2527 in this configuration. If you configured the PXI-2527 in its Independent Topology, you would still be able to perform scanning. Is there any reason you do not want to use the PXI-2527's Independent Topology?
2. The PXI-2527 does not have a cable assembly option for connectivity. We offer a TB-2627 terminal block with screw terminal connectivity, as well as a 100-pin HDI right-angle mating connector (P/N 779311-01) for custom connectivity options. If you are interested in third-party accessories, we recommend the following mating front panel connectors from AMP:
Mating front panel connector, vertical (P/N 533285-1)
Mating front panel connector, right-angle (P/N 532903-2)
Let me know if you have further questions!
Chad Erickson
Switch Product Support Engineer
NI - USA
