PXI-2501 Overview

PXI-2501 Hardware Diagram


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PXI-2501 Topology

The following table lists the topologies supported by the module. Each topology supports immediate and scanning mode.

Topology Software Name
1-wire 48x1 Multiplexer 2501/1-Wire 48x1 Mux (NISWITCH_TOPOLOGY_2501_1_WIRE_48X1_MUX)
1-wire 48x1 Amplified Multiplexer 2501/1-Wire 48x1 Amplified Mux (NISWITCH_TOPOLOGY_2501_1_WIRE_48X1_AMPLIFIED_MUX)
2-wire 24x1 Multiplexer 2501/2-Wire 24x1 Mux (NISWITCH_TOPOLOGY_2501_2_WIRE_24X1_MUX)
2-wire 24x1 Amplified Multiplexer 2501/2-Wire 24x1 Amplified Mux (NISWITCH_TOPOLOGY_2501_2_WIRE_24X1_MUX)
2-wire Dual 12x1 Multiplexer 2501/2-Wire Dual 12x1 Mux (NISWITCH_TOPOLOGY_2501_2_WIRE_DUAL_MUX)
2-wire Quad 6x1 Multiplexer 2501/2-Wire Quad 6x1 Mux (NISWITCH_TOPOLOGY_2501_2_WIRE_QUAD_6X1_MUX)
4-wire 12x1 Multiplexer 2501/4-Wire 12x1 Mux (NISWITCH_TOPOLOGY_2501_4_WIRE_12X1_MUX)
2-wire 4x6 Matrix 2501/2-Wire 4x6 Matrix (NISWITCH_TOPOLOGY_2501_2_WIRE_4X6_MATRIX)

1-Wire 48 × 1 Multiplexer Topology

Connect your signals using the NI TB-2605 terminal block.

1-Wire 48 × 1 Multiplexer


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1-Wire 48 × 1 Amplified Multiplexer


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Connect your signals using the NI TB-2605 terminal block.

In this topology the module operates the same way as the 1-wire 48×1 multiplexer topology except that an amplifier, indicated in the figure above, can be used.

Making a connection

In 1-wire mode, all channels can connect to COM0+. COM0– is always connected to 1_WIRE_LO_REF and can optionally be used to route the second wire of a different signal (for example, the LO terminal of a DMM) through the switch.

During scanning, an example scan list entry is ch2->com0;. This entry routes the signal connected to 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+. To route the signals to AB0, use the niSwitch Connect Channels VI or the niSwitch_Connect function with com0 and ab0.

Pinout

1-Wire 48 × 1 Multiplexer

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Table 1. 1-Wire 48 × 1 Multiplexer Signal Descriptions
Signal Description
1wireREF Signal connection reference
AB0+ Positive analog bus connection
AB0- Negative analog bus connection
CHx Signal connection
COM0+ Routing destination for all channels
COM0- Routing destination for all 1wireREF connections
EXT_TRIG_IN External trigger input connection
GND Ground connection
RSVD Reserved, do not connect
SCAN_ADV Scan advanced output connection
No connection
Table 2. Terminal Block Connections
Software Name Polarity Hardware Name
Module 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–
ab0 + 52 AB0+
18 AB0–
No Connect[1] + 60 COM1+
26 COM1–
No Connect[1] + 44 COM2+
10 COM2–
No Connect[1] + 43 COM3+
9 COM3–
No Connect[1] + 51 AB1+
17 AB1–

2-Wire 24 × 1 Multiplexer Topology

Connect your signals using the NI TB-2605 terminal block.

You can connect to a cold-junction sensor channel for cold-junction compensation.

2-Wire 24 × 1 Multiplexer


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2-Wire 24x1 Amplified Multiplexer


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Making a connection

The module in this topology contains 24 2-wire input channels connected to a common 2-wire channel. In software, these input channels are referred to as ch<0..23> and the common channel is referred to as com0. All positive leads (CH0+ through CH23+) can connect to COM0+, and all negative leads (CH0– through CH23–) can connect to COM0–.

For example, to connect a 2-wire signal to ch5, wire the HI side to CH5+ and the LO side to CH5–. For com0, connect to COM0+ and COM0– for the HI and LO of the signal, respectively.

You can also route cjtemp to com0, which routes com0 to a temperature sensor on the NI TB-2605 terminal block. Refer to Cold-Junction Temperature 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 connected to 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

2-Wire 24 × 1 Multiplexer

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Table 3. 2-Wire 24 × 1 Multiplexer Pinout Signal Descriptions
Signal Description
AB0+ Positive analog bus connection
AB0- Negative analog bus connection
CHx+ Positive signal connection
CHx- Negative signal connection
CJS+ CJC positive connection
CJS- CJC negative connection
COM0+ Routing destination for all positive channels
COM0- Routing destination for all negative channels
EXT_TRIG_IN External trigger input connection
GND Ground connection
RSVD Reserved, no connection
SCAN_ADV Scan advanced output connection
No connection
Table 4. Terminal Block Connections
Software Name Polarity Hardware Name
Module 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–
ab0 + 52 AB0+
18 AB0–
No Connect[2] + 60 COM1+
26 COM1–
No Connect[2] + 44 COM2+
10 COM2–
No Connect[2] + 43 COM3+
9 COM3–
No Connect[2] + 51 AB1+
17 AB1–

2-Wire Dual 12 × 1 Multiplexer Topology

Connect your signals using the NI TB-2605 terminal block.

2-Wire Dual 12 × 1 Multiplexer


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Making a connection

The module 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, ch23 com2

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 Temperature 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

2-Wire Dual 12 × 1 Multiplexer

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Table 5. 2-Wire Dual 12 × 1 Multiplexer Signal Descriptions
Signal Description
ABx+ Positive analog bus connection
ABx- Negative analog bus connection
CHx+ Positive signal connection
CHx- Negative signal connection
CJS+ CJC positive connection
CJS- CJC negative connection
COMx+ Routing destination for corresponding positive signal connections
COMx- Routing destination for corresponding negative signal connections
EXT_TRIG_IN External trigger input connection
GND Ground connection
RSVD Reserved, no connection
SCAN_ADV Scan advanced output connection
No connection
Table 6. Terminal Block Connections
Software Name Polarity Hardware Name
Module 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 Connect* + 60 COM1+
26 COM1–
No Connect* + 43 COM3+
9 COM3–
*Not used in this topology

2-Wire Quad 6×1 Multiplexer Topology

Connect your signals using the NI TB-2605 terminal block.

You can connect to a cold-junction sensor channel for cold-junction compensation.

2-Wire Quad 6 × 1 Multiplexer


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Making a connection

The module in this topology contains four banks of six 2-wire input channels connected to a common 2-wire channel. These input channels are referred to as ch<0..23>, and the four common channels are referred to as com<0..3>. You can only connect to the common channel that is in the same bank. The banks are organized as shown in the following table.

Input Channels Common Channel
ch0, ch1, ch2, ch3, ch4, ch5, cjtemp com0
ch6, ch7, ch8, ch9, ch10, ch11 com1
ch12, ch13, ch14, ch15, ch16, ch17 com2
ch18, ch19, ch20, ch21, ch22, ch23 com3

For example, you can connect ch5 to com0; however, you cannot connect ch5 to com1 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 Temperature 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 connected to CH2– is routed 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+. To route the signals to ABO, use the niSwitch Connect Channels VI or the niSwitch_Connect function with com0 and ab0 and the signal connected to CH2– is routed to COM0–.

Pinout

2-Wire Quad 6 × 1 Multiplexer

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Table 7. 2-Wire Quad 6 × 1 Multiplexer Signal Descriptions
Signal Description
ABx+ Positive analog bus connection
ABx- Negative analog bus connection
CHx+ Positive signal connection
CHx- Negative signal connection
CJS+ CJC positive connection
CJS- CJC negative connection
COMx+ Routing destination for corresponding positive signal connections
COMx- Routing destination for corresponding negative signal connections
EXT_TRIG_IN External trigger input connection
GND Ground connection
RSVD Reserved, no connection
SCAN_ADV Scan advanced output connection
No connection
Table 8. Terminal Block Connections
Software Name Polarity Hardware Name
Module 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–
com1 + 60 COM1+
26 COM1–
com2 + 44 COM2+
10 COM2–
com3 + 43 COM2+
9 COM2–
ab0 + 52 AB0+
18 AB0–
ab (Not used in this topology) + 51 AB1+
17 AB1–

4-Wire 12 × 1 Multiplexer Topology

Connect your signals using the NI TB-2605 terminal block.

4-Wire 12 × 1 Multiplexer


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4-wire Resistance Measurements

4-wire mode is usually used in 4-wire resistance measurements. One pair of wires supplies the excitation while the other pair makes the voltage measurement. In 4-wire mode, connect your excitation or source leads to CHxA+ and CHxA-, and connect your measurement or sensing leads to CHxB+ and CHxB-, as shown in the following figure.


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Note The previous figure shows the DMM connected to the analog bus (AB) of the switch module. Instead of routing signals to the AB, you can connect COM0A+ and COM0A- to the excitation terminals and COM0B+ and COM0B- to the sense terminals of the DMM.

Making a connection

Both the scanning command, ch2->com0;, and the immediate operation, niSwitch Connect Channels VI or the niSwitch_Connect function with parameters ch2 and com0, result in the following connections:

  • signal connected to CH2A+ is routed to COM0A+
  • signal connected to CH2A– is routed to COM0A–
  • signal connected to CH2B+ is routed to COM0B+
  • signal connected to CH2B– is routed to COM0B–

Pinout

4-Wire 12 × 1 Multiplexer

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Table 9. 4-Wire 12 × 1 Multiplexer Signal Descriptions
Signal Description
ABx+ Positive analog bus connection
ABx- Negative analog bus connection
CHxA+ Positive excitation connection
CHxA- Negative excitation connection
CHxB+ Positive sense connection
CHxB- Negative sense connection
COM0x+ Routing destination for positive channels on the corresponding bank
COM0x- Routing destination for negative channels on the corresponding bank
EXT_TRIG_IN External trigger input connection
GND Ground connection
RSVD Reserved, no connection
SCAN_ADV Scan advanced output connection
No connection
Table 10. Terminal Block Connections
Software Name Polarity Hardware Name
Module Connector Pin Number NI TB-2605 Terminal Name
ch0 + 67 CH0A+
- 33 CH0A-
+ 50 CH0B+
- 16 CH0B-
ch1 + 66 CH1A+
- 32 CH1A-
+ 49 CH1B+
- 15 CH1B-
ch2 + 65 CH2A+
- 31 CH2A-
+ 48 CH2B+
- 14 CH2B-
ch3 + 64 CH3A+
- 30 CH3A-
+ 47 CH3B+
- 13 CH3B-
ch4 + 63 CH4A+
- 29 CH4A-
+ 46 CH4B+
- 12 CH4B-
ch5 + 62 CH5A+
- 28 CH5A-
+ 45 CH5B+
- 11 CH5B-
ch6 + 59 CH6A+
- 25 CH6A-
+ 40 CH6B+
- 6 CH6B-
ch7 + 58 CH7A+
- 24 CH7A-
+ 39 CH7B+
- 5 CH7B-
ch8 + 57 CH8A+
- 23 CH8A-
+ 38 CH8B+
- 4 CH8B-
ch9 + 55 CH9A+
- 21 CH9A-
+ 37 CH9B+
- 3 CH9B-
ch10 + 54 CH10A+
- 20 CH10A-
+ 36 CH10B+
- 2 CH10B-
ch11 + 53 CH11A+
- 19 CH11A-
+ 35 CH11B+
- 1 CH11B-
com0 + 61 COM0A+
- 27 COM0A-
+ 44 COM0B+
- 10 COM0B-
No Connect (Not used in this topology) + 60 COM1A+
- 26 COM1A-
+ 43 COM1B+
- 9 COM1B-
ab0 + 52 AB0A+
- 18 AB0A-
+ 51 AB0B+
- 17 AB0B-

2-Wire 4 × 6 Matrix Topology

Connect your signals using the NI TB-2606 terminal block.

2-Wire 4 × 6 Matrix


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Making a connection

In this topology, connect your positive and negative leads to Cx± or Rx± inside the NI TB-2606 terminal block.

During scanning, an example scan list entry is r2->c1;. This entry routes the signal connected to R2+ to C1+ and connects R2– to C1–.

During immediate operations when calling the niSwitch Connect Channels VI or the niSwitch_Connect function with r2 and c1, the signal connected to R2+ is routed to C1+ and the signal connected to R2– is routed to C1–. To route the signals to AB0, use the niSwitch Connect Channels VI or the niSwitch_Connectfunction with com0 and ab0.

Pinout

2-Wire 4 × 6 Matrix

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Table 11. 2-Wire 4 × 6 Matrix Signal Descriptions
Signal Description
ABx+ Positive analog bus connection
ABx- Negative analog bus connection
COLx+ Positive column connection
COLx- Negative column connection
EXT_TRIG_IN External trigger input connection
GND Ground connection
RSVD Reserved, no connection
ROWx+ Positive row connection
ROWx- Negative row connection
SCAN_ADV Scan advanced output connection
No connection
Table 12. Terminal Block Connections
Software Name Polarity Hardware Name
Module Connector Pin Number NI TB-2606 Terminal Name
c0 + 67, 59, 50, 40 C0+
- 33, 25, 16, 6 C0-
c1 + 66, 58, 49, 39 C1+
- 32, 24, 15, 5 C1-
c2 + 65, 57, 48, 38 C2+
- 31, 23, 14, 4 C2-
c3 + 64, 55, 47, 37 C3+
- 30, 21, 13, 3 C3-
c4 + 63, 54, 46, 36 C4+
- 29, 20, 12, 2 C4-
c5 + 62, 53, 45, 35 C5+
- 28, 19, 11, 1 C5-
r0 + 61 R0+
- 27 R0-
r1 + 60 R1+
- 26 R1-
r2 + 44 R2+
- 10 R2-
r3 + 43 R3+
- 9 R3-
ab0 + 52 AB0+
- 18 AB0-
ab1 + 51 AB1+
- 17 AB1-

PXI-2501 Amplifier

The module has an amplifier with a gain of 1. This amplifier can be switched in-line before the COM0 signal and the AB0 signal. The amplifier helps decrease the settling time of the FET switch. The high-impedance amplifier isolates the Field-effect transistor (FET) switches from the resistance, capacitance, and inductance in the external wiring. This isolation decreases the resistance/capacitance time constant seen by the FET, which improves settling time. When the amplifier is used, the switch module becomes directional, where CHx is for signal inputs and COM0 or AB0 are for signal outputs.

The amplifier has an offset that can be calibrated for more accurate measurements. The calibration data can be stored into and retrieved from the EEPROM on the module.

The module also has an amplifier in the CJS0+ to COM0+ signal path. This amplifier in the cold-junction sensor signal path is used to improve settling time performance. It prevents the impedance of the cold-junction sensor from increasing the settling time when switching the CJS channel. As a result, when scanning thermocouples, the settling time for the cold-junction sensor channel should be about the same as for the channels with the thermocouples.

PXI-2501 Cold-Junction Temperature Sensor Channel

The module has a dedicated temperature sensor channel useful for cold-junction compensation when switching thermocouples. The NI TB-2605 and TBX-68S terminal blocks both have onboard temperature sensors that connect to the dedicated cold-junction sensor channel. You can access the cold-junction sensor channel by connecting to channel cjtemp in the 2-wire 24×1 multiplexer, 2-wire dual 12×1 multiplexer, and 2-wire quad 6×1 multiplexer topologies.

PXI-2501 Current-Loop Receivers

The module has sockets for transforming individual channels to current-to-voltage converters. NI offers a process-current pack of four 249 Ω, 0.1%, 5 ppm, 0.25 W resistors. The reference designator format for the current-loop resistors is such that for input channel x, the resistor is RCLx. For example, the resistor for channel 14 is RCL14.

Note Before installing the resistors in your module, make sure that no signals are connected to your module front connector.

Before installing your module in the NI PXI chassis, you must install the resistors by performing the following steps:

  1. Ground yourself using a grounding strap or a ground connected to your PXI chassis. Properly grounding yourself prevents damage to your PXI module from electrostatic discharge.
  2. Bend and trim the resistor lead as shown in the following figure. Be sure that the resistor does not extend more than 0.5 in. (1.3 cm) above the surface of the circuit board.
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  3. Insert the resistor into the appropriate socket, labeled RCLx.

PXI-2501 Expansion

Matrix Expansion

To expand the matrix of a module, directly connect wire from one terminal block to the other using the NI TB-2606 terminal block. Each module can operate as a 4×6 matrix. To form a 4×12 matrix, use two modules and connect all the rows from both TB-2606 terminal blocks.

To form a 12×6 matrix, you need three modules with three TB-2606 terminal blocks. Connect all the columns from all three terminal blocks.

Note The analog bus connectors cannot be used to expand a matrix.

Multiplexer Expansion

If you need to multiplex through more channels than the number present on your module, you can expand the size of the multiplexer. The NI TB-2605 terminal block has two analog bus connectors that allow analog bus sharing between two other modules. Each NI TB-2605 comes with a plug to share this analog bus between modules.

Refer to the module hardware diagram to see the analog bus relay that connects the multiplexer COM lines to an analog bus. This analog bus relay must be closed for multiplexer expansion. When this analog bus is shared between modules, a single larger multiplexer is formed. For example, connecting two modules using their analog bus in 2-wire 24×1 multiplexer topology, creates a 2-wire 48×1 multiplexer.

You can also use the LV6-BAN4 cable to connect a DMM directly to the analog bus that acts as the COM of the expanded multiplexer.

1 Not used in this topology

2 Not used in this topology