NI PXIe-7868R User Manual
- Updated2023-02-20
- 6 minute(s) read
NI PXIe-7868R User Manual
This document provides compliance, pinout, connectivity, mounting, and power information for the NI PXIe-7868R.
Hardware Overview
The following high-level block diagram represents the NI PXIe-7868R.
Pinout
| Signal | Description |
|---|---|
| AI+ | Positive analog input signal connection |
| AI- | Negative analog input signal connection |
| AISENSE | Reference connection for NRSE measurements |
| AIGND | Ground reference for the analog input signal |
| AO | Analog output signal connection |
| AOGND | Ground reference for the analog output signal |
| DIO | Digital input/output signal connection |
| DGND | Ground reference for the digital signal |
| EXTCLKIN | External clock input source that can be used for source synchronous acquisitions. The provided clock source must be stable and glitch-free. |
| GND | Ground connection |
| Supply (+5 Vout) | 5 V power output connection for external devices |
| NC | No connection |
The NI PXIe-7868R is protected from overvoltage and overcurrent conditions.
Connectivity Options
Use the following connection accessories and cables to access the signals on the I/O connectors.
| Connector Type | Accessory | Description | NI Part Number |
|---|---|---|---|
| RDIO | NI SCB-68 HSDIO | Shielded 68-Pin Connector Block for R Series DIO and HSDIO Products | 782914-01 |
| NI SHC68-C68-RDIO2 | Shielded R Series High Speed Digital Cable (1 m) | 156166-01 | |
| Shielded R Series High Speed Digital Cable (2 m) | 156166-02 | ||
| RMIO/RAO | NI SCB-68A | Noise Rejecting, Shielded I/O Connector Block | 782536-01 |
| NI SHC68-68-RMIO | RMIO Shielded Cable, 68 pin D-Type to 68 pin VHDCI (1 m) | 189588-01 | |
| RMIO Shielded Cable, 68 pin D-Type to 68 pin VHDCI (2 m) | 189588-02 |
Analog Input
The NI PXIe-7868R provides connections for six AI channels. Each channel has an AI+ pin, AI- pin, and AIGND pin to which you can connect both single-ended or differential voltage signals. Use the AISENSE pin to connect non-referenced single-ended signals.
Connecting Single-Ended Voltage Signals
To connect referenced single-ended voltage signals to the NI PXIe-7868R, you must connect the voltage ground signal to AI GND in order to keep the common-mode voltage in the specified range.
To connect non-referenced single-ended voltage signals to the NI PXIe-7868R, you must connect the voltage ground signal to AI SENSE in order to keep the common-mode voltage in the specified range.
Connecting Differential Voltage Signals
You can connect grounded or floating differential signal sources to the NI PXIe-7868R. Connect the positive voltage signal to the AI+ and the negative voltage signal to AI-. To connect grounded differential signals to the NI PXIe-7868R, you must also connect the signal reference to AI GND.
To connect floating differential signals to the NI PXIe-7868R, you must connect the negative and positive signals to AI GND through 1 MΩ resistors to keep the voltage within the common-mode voltage range. If the voltage source is outside the common-mode voltage range, the NI PXIe-7868R does not read data accurately.
Analog Output
The NI PXIe-7868R provides connections for eighteen analog output channels. Each channel has an AO pin and AOGND pin to which you can connect a load.
Digital I/O
The NI PXIe-7868R provides connections for 48 digital input/output (DIO) channels. Connector 0 contains 16 low-speed channels that can run up to 10 MHz signal frequencies and Connector 1 contains 32 high-speed DIO channels that can run up to 80 MHz signal frequencies. Each connector has a fixed logic level of 3.3 V. You can configure each channel as input or output.
- Low-speed signal frequencies up to 10 MHz with logic levels configured as 3.3 V.
- High-speed signal frequencies up to 80 MHz with logic levels configured as 3.3 V.
- LED
The DIO channels connect to the FPGA through buffers, which have overvoltage and undervoltage protection as well as over current protection. Refer to the device specifications on ni.com/manuals for more information about the maximum voltage and current.
When the system powers on, the DIO channels are set as input low with pull-down resistors. To set another power-on state, you can configure the NI PXIe-7868R to load a VI when the system powers on. The VI can then set the DIO lines to any power-on state. Visit ni.com/info and enter RSeries_PowerUpStates to learn more about configuring the power-up states for the NI PXIe-7868R.
All the high-speed DIO channels on Connector 1 are routed with a 50 Ω characteristic trace impedance. Route all external circuitry with a similar impedance to ensure best signal quality. NI recommends performing signal integrity measurements to test the affect of signal routing with the cable and connection accessory for your application.
Field Wiring Considerations
Environmental noise can seriously affect the measurement accuracy of the device if you do not take proper care when running signal wire between signal sources and the device. The following recommendations mainly apply to AI signal routing to the device, as well as signal routing in general.
- Use differential AI connections to reject common-mode noise.
- Use individually shielded, twisted-pair wires to connect AI signals to the device. With this type of wire, the signal attached to the positive and negative inputs are twisted together and then covered with a shield. You then connect this shield only at one point to the signal source ground. This kind of connection is required for signals traveling through areas with large magnetic fields or high electromagnetic interference.
- Route signals to the device carefully. Keep cabling away from noise sources, such as video monitors and analog signals.
- Separate NI PXIe-7868R signal lines from high-current or high-voltage lines. These lines can induce currents in or voltages on the NI PXIe-7868R signal lines if they run in parallel paths at a close distance. To reduce the magnetic coupling between lines, separate them by a reasonable distance if they run in parallel or run the lines at right angles to each other.
- Do not run signal lines through conduits that also contain power lines.
- Protect signal lines from magnetic fields caused by electric motors, welding equipment, breakers, or transformers by running them through special metal conduits.
- To minimize signal-to-signal skew within each digital channel, maintain signal lines' length within 1 inch of difference.
+5 V Power Source
Use the +5 V terminals on the I/O connector supply +5 V referenced to DGND to power external circuitry.
The power rating is 4.75 to 5.1 V DC at 0.5 A.
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