NI PXI-2501/2503 2-Wire Dual 12×1 Multiplexer Topology

NI Switches Help

Edition Date: April 2015

Part Number: 375472H-01

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When using the NI PXI-2501/2503 as a 2-wire dual 12×1 multiplexer, connect your signals using the NI TB-2605 terminal block. In this topology, you can connect to a Cold-Junction Sensor Channel for cold-junction compensation. The following figure is a representation of the NI PXI-2501/2503 in this mode.

Making a Connection

The NI PXI-2501/2503 in this topology contains two banks of 12 2-wire input channels connected to a common 2-wire channel. These input channels are referred to as ch<0..23> and the two common channels are referred to as com0 and com2. You can only connect to the common channel that is in the same bank. The banks are organized as follows:

Input Channels Common Channel
ch0, ch1, ch2, ch3, ch4, ch5, ch6, ch7, ch8, ch9, ch10, ch11, cjtemp com0
ch12, ch13, ch14, ch15, ch16, ch17, ch18, ch19, ch20, ch21, ch22, ch23com2

For example, you can connect ch5 to com0; however, you cannot connect ch5 to com2 in this topology. When connecting signals for ch5, you would connect them to CH5+ and CH5– for HI and LO of the signal, respectively. For com0, connect to COM0+ and COM0– for HI and LO of the signal, respectively.

Notice that in the first bank you can connect cjtemp to com0. This connects com0 to a temperature sensor on the NI TB-2605 terminal block. Refer to Cold-Junction Sensor Channel for more information.

During scanning, an example scan list entry is ch2->com0;. This entry routes the signal connected to CH2+ to COM0+ and the signal from CH2– to COM0–.

During immediate operations when calling the niSwitch Connect Channels VI or the niSwitch_Connect function with ch2+ and com0, the signal connected to CH2+ is routed to COM0+ and the signal connected to CH2– is routed to COM0–. To route the signals to AB0, use the niSwitch Connect Channels VI or the niSwitch_Connect function with com0 and ab0.

Pinout

The following figure and tables identify the pins for the NI PXI-2501/2503 in the 2-wire dual 12×1 multiplexer topology.

Caution  Do not connect to RESERVED pins.
Software Name Polarity Hardware Name
NI PXI-2501/2503
Connector Pin Number
NI TB-2605
Terminal Name
ch0 + 67 CH0+
33 CH0–
ch1 + 66 CH1+
32 CH1–
ch2 + 65 CH2+
31 CH2–
ch3 + 64 CH3+
30 CH3–
ch4 + 63 CH4+
29 CH4–
ch5 + 62 CH5+
28 CH5–
ch6 + 59 CH6+
25 CH6–
ch7 + 58 CH7+
24 CH7–
ch8 + 57 CH8+
23 CH8–
ch9 + 55 CH9+
21 CH9–
ch10 + 54 CH10+
20 CH10–
ch11 + 53 CH11+
19 CH11–
ch12 + 50 CH12+
16 CH12–
ch13 + 49 CH13+
15 CH13–
ch14 + 48 CH14+
14 CH14–
ch15 + 47 CH15+
13 CH15–
ch16 + 46 CH16+
12 CH16–
ch17 + 45 CH17+
11 CH17–
ch18 + 40 CH18+
6 CH18–
ch19 + 39 CH19+
5 CH19–
ch20 + 38 CH20+
4 CH20–
ch21 + 37 CH21+
3 CH21–
ch22 + 36 CH22+
2 CH22–
ch23 + 35 CH23+
1 CH23–
com0 + 61 COM0+
27 COM0–
com2 + 44 COM2+
10 COM2–
ab0 + 52 AB0+
18 AB0–
ab1 + 51 AB1+
17 AB1–
No Connect1 + 60 COM1+
26 COM1–
No Connect1 + 43 COM3+
9 COM3–
1 Not used in this topology

Additional Pin References

NI PXI-2501/2503
Connector Pin Number
Signal name
7, 56 GND
41 TRIG IN
42 SCANADV
8 RESERVED
68 CJS+
34 CJS-
22 1wireREF

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