PXI-6239 Bank-Isolated Current Input and Output Module
Земля PXI-6239 is a bank-isolated PXI multifunction data acquisition module designed specifically for current measurement and current generation. It provides eight differential ±20 mA analog inputs, two programmable 0 mA to 20 mA analog outputs, six industrial digital inputs and four sinking digital outputs.
With 16-bit resolution, a maximum analog input sampling rate of 250 kS/s and hardware-timed current outputs, the PXI-6239 is suitable for industrial process control, current-loop testing, automated test equipment and monitoring systems. Two 32-bit counter/timers and PXI backplane synchronization support encoder, flow-meter, pulse and coordinated measurement applications.
Key Features of the PXI-6239
- Eight differential current input channels
- ±20 mA analog input range
- 16-bit analog input resolution
- 250 kS/s maximum aggregate sampling rate
- 700 kHz typical small-signal input bandwidth
- 92 Ω nominal differential input impedance
- Two hardware-timed current outputs
- 0 mA to 20 mA analog output range
- 16-bit analog output resolution
- 500 kS/s maximum single-channel output rate
- 450 kS/s per channel with both outputs active
- Six isolated 0 V to 30 V digital inputs
- Four isolated sinking digital outputs
- Up to 350 mA with one digital output active
- Two 32-bit counter/timers
- Programmable digital input debounce filters
- Digital triggering and PXI synchronization
- Bank-isolated field I/O architecture
- 37-pin D-Sub front connector
- NI-DAQmx software support
PXI-6239 Technical Specifications
| Product Model | PXI-6239 |
|---|---|
| Part Number | 779626-01 |
| Product Family | Isolated M Series multifunction DAQ |
| Primary Measurement Type | Current input and current output |
| Шинный интерфейс | PXI, compatible with PXI and PXI Express hybrid slots |
| Analog Input Channels | 8 differential current inputs |
| Analog Input Resolution | 16 bits |
| Maximum Analog Input Sample Rate | 250 kS/s aggregate |
| Simultaneous Sampling | No; multiplexed input architecture |
| Analog Input Range | ±20 мА |
| Input Coupling | DC |
| Analog Input Impedance | 92 Ω ±10% in parallel with 100 pF |
| Maximum Input Impedance | 100 Ω at 55°C |
| Small-Signal Input Bandwidth | 700 kHz typical at -3 dB |
| Analog Input FIFO | 4,095 samples |
| Scan List Memory | 4,095 entries |
| Analog Input Overcurrent Protection | ±40 mA maximum |
| Analog Output Channels | 2 current outputs |
| Analog Output Resolution | 16 bits |
| Analog Output Range | 0 mA to 20 mA |
| Maximum Single-Channel Output Rate | 500 kS/s |
| Maximum Dual-Channel Output Rate | 450 kS/s per channel |
| Analog Output Slew Rate | 0.1 mA/µs |
| Analog Output FIFO | 8,191 samples shared between active channels |
| Analog Output External Supply | 10 VDC to 30 VDC |
| Maximum Resistive Load | Up to 1 kΩ with a 24 V external supply |
| Digital Inputs | 6 isolated input channels |
| Digital Input Range | 0 V to 30 V |
| Digital Input Logic Low | 0 V to 4 V |
| Digital Input Logic High | 10 V to 30 V |
| Digital Outputs | 4 isolated sinking outputs |
| Maximum Digital Output Supply | 30 VDC |
| Digital Output Current | 100 mA per line with simultaneous operation; 350 mA with one line active |
| Counter/Timers | 2 |
| Counter Resolution | 32 bits |
| Digital Filter Settings | 125 ns, 6.425 µs, 2.56 ms or disabled |
| Trigger Bus | PXI_TRIG lines 0 through 7 and PXI_STAR |
| Front Connector | 37-pin D-Sub |
| Operating Temperature | 0°C to 55°C |
| Storage Temperature | -20°C to 70°C |
| Weight | Approximately 144 g |
| Поддержка программного обеспечения | НИ-DAQmx |
| Lifecycle Status | Discontinued with limited NI support |
PXI-6239 Part Number and Accessories
| Item | Part Number | Описание |
|---|---|---|
| PXI-6239 | 779626-01 | Eight-channel isolated current input and two-channel current output PXI module |
| SH37F-37M Cable | 778621-02 | 2 m shielded 37-pin female-to-male D-Sub cable |
| R37F-37M Cable | 779195-01 | 1 m low-cost unshielded 37-pin ribbon cable |
| SH37F-P-4 Cable | 778620-04 | 4 m shielded 37-pin D-Sub to pigtail cable for custom wiring |
| CB-37F-HVD | 779491-01 | High-voltage DIN-rail screw-terminal connector block |
| CB-37FH | 778673-01 | Horizontal DIN-rail 37-pin D-Sub screw-terminal block |
| CB-37FV | 778672-01 | Vertical DIN-rail 37-pin D-Sub screw-terminal block |
| CB-37F-LP | 779353-01 | Low-profile 37-pin connector block |
| TB-2621 | 779444-01 | PXI-mounted high-voltage screw-terminal block |
Verify connector-block voltage ratings, cable shielding and field-wiring requirements before ordering. The PXI-6239 shares a 37-pin connector with several NI modules, but identical connector size does not guarantee identical pin assignments.
Current I/O Architecture
Unlike voltage-oriented multifunction modules, the PXI-6239 measures and generates current directly. Its eight analog inputs are designed for current signals in the ±20 mA range, while its two analog outputs generate programmable current from 0 mA to 20 mA.
This configuration is useful for testing current-loop transmitters, industrial controllers and electronic interfaces without adding separate voltage-to-current or current-to-voltage conversion hardware.
Eight Differential Current Inputs
The PXI-6239 provides eight differential analog input channels. Each channel measures the current flowing between its positive and negative input terminals through an internal precision input impedance.
Differential inputs provide a defined current path and help reduce noise coupled equally onto the two signal conductors. All eight channels are part of the isolated analog input bank rather than being individually isolated.
±20 mA Input Range
The analog input range is fixed at ±20 mA, allowing the module to measure both positive and negative current flow. This supports common industrial 0–20 mA and 4–20 mA signals as well as bipolar current measurements.
The inputs should not be treated as general-purpose voltage channels. Applying voltage without considering the internal impedance can produce excessive current and permanently damage the module.
16-Bit Current Measurement
The analog input converter provides 16-bit resolution. Across the full bipolar ±20 mA span, the converter supplies 65,536 theoretical quantization levels before noise, accuracy and calibration effects are considered.
NI specifies approximately 18.9 µA absolute accuracy at full scale under the documented calibration assumptions and approximately 0.24 µA sensitivity. Actual performance depends on temperature, calibration interval and measurement configuration.
250 kS/s Multiplexed Sampling
The eight current inputs share a multiplexed ADC with a maximum aggregate sampling rate of 250 kS/s. The module does not sample every channel simultaneously.
When multiple channels are included in a task, the total conversion rate is divided among those channels. Applications that require precise phase relationships should account for the conversion delay between adjacent channels.
700 kHz Input Bandwidth
The analog current inputs have a typical small-signal bandwidth of approximately 700 kHz at the -3 dB point. The usable measurement bandwidth also depends on the selected sample rate and the spectral content of the input signal.
For repetitive or dynamic current signals, choose a sampling rate high enough to represent the waveform while accounting for aliasing and channel-scanning timing.
Analog Input Protection
The analog inputs incorporate overcurrent and overvoltage protection, but these features have defined limits. Current exceeding approximately ±40 mA can permanently damage the device.
Use external current limiting and protection when a wiring fault could connect the input to a high-energy voltage source. Internal protection should not replace appropriately rated system-level protection.
Two 0–20 mA Current Outputs
The PXI-6239 provides two 16-bit current output channels with a programmable range of 0 mA to 20 mA. These channels can simulate transmitters, generate controller setpoints and exercise current-input devices.
One output can update at up to 500 kS/s. When both outputs are active, each can update at up to 450 kS/s, allowing hardware-timed dynamic current generation rather than only static setpoints.
External Power for Current Outputs
The current outputs require a user-provided supply from 10 VDC to 30 VDC. The external supply provides the compliance voltage necessary to drive current through the connected load.
With a 24 V supply, the module supports a resistive load of up to approximately 1 kΩ under specified conditions. Available load resistance decreases when a lower supply voltage is used or additional voltage drop is present in the wiring.
Current Output Protection
The current outputs include open-circuit and short-circuit protection. Their default power-on state is 0 mA, and the specified design avoids a power-on output glitch.
Open-circuit protection does not eliminate the need to verify external supply polarity and wiring. Incorrect field connections can still damage the module or connected equipment.
Six Industrial Digital Inputs
Six digital input channels accept signals from 0 V to 30 V. A voltage from 0 V to 4 V is recognized as logic low, while 10 V to 30 V is recognized as logic high.
These inputs can monitor proximity sensors, limit switches, alarms, relay contacts, PLC outputs, encoders and other industrial field devices. At a 24 V input level, typical current is approximately 7 mA.
Programmable Digital Debounce Filters
Each digital input supports programmable debounce filtering with settings of 125 ns, 6.425 µs, 2.56 ms or disabled. Filtering can reject short noise pulses and mechanical contact bounce.
Select the shortest interval that reliably removes unwanted transitions without hiding valid pulses. High-speed encoder and timing signals normally require a shorter filter than switches or relay contacts.
Four Sinking Digital Outputs
The PXI-6239 has four isolated sinking outputs. When an output is active, it provides a low-side current path from the connected load to the digital output bank ground.
All four outputs can sink up to 100 mA per line simultaneously. When only one output is active, that line can sink up to 350 mA under the specified operating conditions.
External Digital Output Supply
The digital output bank supports an external field supply of up to 30 VDC. The load is normally connected between the positive field supply and the selected sinking output.
The field supply, load, wiring and connector block must be rated for the required voltage and current. Use external fusing when a supply can deliver damaging fault current.
Inductive Load Control
The sinking outputs can control compatible relay coils, valves and other inductive loads. A flyback diode, snubber or transient suppressor should be installed across the load to limit reverse voltage when the current is interrupted.
Without suppression, repetitive inductive transients can interfere with analog measurements and reduce output reliability.
Two 32-Bit Counter/Timers
Two general-purpose 32-bit counter/timers support edge counting, period measurement, pulse-width measurement, semi-period measurement, two-edge separation and pulse generation.
Position-measurement functions include X1, X2 and X4 quadrature encoder decoding with index-channel reloading. The counter signals use the module’s isolated digital terminals.
Bank-Isolated Design
The analog input, analog output and digital I/O sections are isolated from the PXI chassis and system ground according to the module’s bank architecture. Isolation helps reduce ground loops and prevents field-side noise from directly entering the computer ground.
Channels within a bank share their corresponding ground reference and are not isolated individually from one another. Review the official isolation diagram when connecting signals that use different field references.
Digital Triggering and Synchronization
The PXI-6239 supports start, reference and pause triggers for analog acquisition. Analog output operations support start and pause triggering, while the counter/timers support gate, source, arm, auxiliary and encoder signals.
Timing signals can be routed through PXI_TRIG lines 0 through 7 and PXI_STAR. This allows the module to coordinate acquisition and generation with compatible PXI instruments without external trigger cables.
Typical PXI-6239 Applications
- 4–20 mA transmitter testing
- Промышленное управление технологическими процессами
- Current-loop simulation
- PLC analog I/O validation
- Автоматизированное испытательное оборудование
- Valve and pump control
- Flow-meter measurement
- Encoder and position monitoring
- Proximity sensor acquisition
- Industrial controller testing
- Production test fixtures
- Laboratory automation
- Electromechanical system testing
4–20 mA Transmitter Testing
The current inputs can directly measure outputs from compatible 4–20 mA transmitters. Test software can verify zero, span, linearity and response time across multiple devices or channels.
The two current outputs can simulate 4–20 mA transmitters to test PLCs, distributed control systems and data acquisition inputs. An external 10 VDC to 30 VDC supply is required for current generation.
Industrial Process Control
The PXI-6239 can monitor current-loop sensors while generating current setpoints for industrial equipment. Digital inputs can record machine states, and sinking outputs can operate relays or compatible field loads.
This mixed-I/O architecture allows one PXI module to combine process measurement, control and timing functions.
PLC and Controller Validation
The module can simulate current transmitters connected to PLC analog inputs and measure current generated by PLC analog outputs. Digital channels can apply or verify associated status, alarm and control signals.
Hardware-timed current generation supports dynamic tests that cannot be performed with a static current source alone.
NI-DAQmx Software Support
The PXI-6239 is controlled through the NI-DAQmx driver. NI-DAQmx provides functions for current input, current output, digital I/O, counter measurements, hardware timing, triggering and PXI signal routing.
The module can be integrated with LabVIEW, LabWindows/CVI, C/C++ and compatible .NET environments. NI Measurement & Automation Explorer can identify the module and perform basic diagnostic operations.
PXI-6239 Lifecycle Status
The PXI-6239 is discontinued and listed by NI with limited support. It may remain appropriate for maintaining existing test systems that depend on its current I/O, 37-pin wiring and NI-DAQmx configuration.
For new projects, confirm the availability of compatible current hardware and consider whether a newer PXI Express or C Series measurement system provides a more suitable long-term platform.
PXI-6239 Troubleshooting
The PXI-6239 is not detected in NI MAX
Confirm that the module is fully seated in a compatible PXI or PXI hybrid slot. Check chassis power, controller communication and NI-DAQmx installation, then restart the system.
A current input always reads zero
Verify that the current loop is complete and that current flows through the positive and negative input terminals. Check field-supply polarity and confirm that the source is operating.
The current input reading is too high
Check whether another shunt resistor or measurement device has been connected incorrectly. Confirm that the current remains within the ±20 mA range and never exceeds the protection limit.
A 4–20 mA transmitter cannot drive the input
Calculate the total loop resistance, including the PXI-6239 input impedance, cable resistance and other connected devices. Confirm that the transmitter’s supply provides sufficient compliance voltage.
A current output remains at 0 mA
Verify that a 10 VDC to 30 VDC external supply is connected to the analog output power terminals. Check supply polarity, load wiring and the programmed output channel.
A current output cannot reach 20 mA
Reduce the load resistance or increase the external supply voltage within the specified range. With a 24 V supply, maximum resistive load is approximately 1 kΩ under the specified conditions.
A sinking digital output does not operate the load
Confirm that the load is connected between the positive field supply and the output. Check the output-bank ground, supply polarity and load current.
Digital inputs change unexpectedly
Inspect the field wiring for electrical noise and poor grounding. Enable an appropriate debounce filter and route digital cables away from motors, contactors and variable-frequency drives.
Counter measurements are unstable
Check pulse amplitude, edge quality, wiring and grounding. Configure a suitable digital filter while ensuring that the filter does not reject valid high-frequency pulses.
PXI-6239 Comparison with Similar Isolated DAQ Modules
| Модель | Analog Inputs | Analog Outputs | Digital Output Type | Best Suited For |
|---|---|---|---|---|
| PXI-6233 | 16 voltage inputs | 2 voltage outputs | Sinking | Isolated voltage measurement and low-side control |
| PXI-6236 | 4 current inputs | Ничего | Источники | Lower-channel-count current acquisition |
| PXI-6238 | 8 ±20 mA inputs | 2 × 0–20 mA outputs | Источники | Current I/O with high-side digital control |
| PXI-6239 | 8 ±20 mA inputs | 2 × 0–20 mA outputs | Sinking | Current I/O with low-side digital control |
| PXI-6704 | Ничего | 16 static current outputs plus voltage outputs | General-purpose digital I/O | High-channel-count static current generation |
PXI-6239 vs PXI-6238
Земля PXI-6238 and PXI-6239 both provide eight ±20 mA inputs and two hardware-timed 0–20 mA outputs. Their primary difference is the industrial digital output architecture.
The PXI-6238 uses sourcing digital outputs, while the PXI-6239 uses sinking outputs. Choose the PXI-6239 for NPN-style, low-side load control and the PXI-6238 for PNP-style, high-side control.
PXI-6239 vs PXI-6233
Земля PXI-6233 is designed for voltage I/O, providing 16 voltage inputs and two ±10 V voltage outputs. The PXI-6239 is designed for current I/O, providing eight ±20 mA inputs and two 0–20 mA outputs.
Both modules include six industrial digital inputs, four sinking digital outputs and two 32-bit counters. Select the model according to whether the field instrumentation communicates using voltage or current.
PXI-6239 vs PXI-6704
Земля PXI-6704 provides a larger number of static current and voltage output channels but does not provide the PXI-6239’s current inputs or high-speed hardware-timed current output capability.
Select the PXI-6239 for bidirectional current-loop testing and dynamic waveform generation. Select the PXI-6704 when the application mainly needs numerous static current setpoints.
Recommended Related Products
- PXI-6238 Isolated Current I/O Module with Sourcing Outputs
- PXI-6233 Isolated Voltage I/O Module with Sinking Outputs
- PXI-6236 Isolated Current Input Module
- PXI-6704 High-Channel-Count Analog Output Module
- PCI-6239 Bank-Isolated Current I/O Device
- View More NI PXI and PXI Express Modules
- View More NI PCI and USB Data Acquisition Products
Selecting the Right Isolated Current I/O Module
Choose the PXI-6239 when the application requires eight high-speed current inputs, two hardware-timed 0–20 mA outputs, industrial digital inputs and sinking digital control.
Select the PXI-6238 when the field wiring requires sourcing digital outputs. Choose the PXI-6233 for voltage rather than current I/O, or the PXI-6704 when additional static current outputs are required.
Why Choose the PXI-6239?
- Directly measures eight ±20 mA current signals
- Generates two programmable 0–20 mA outputs
- Supports hardware-timed current generation
- Provides 16-bit input and output resolution
- Acquires current signals at up to 250 kS/s
- Includes six industrial digital inputs
- Provides four sinking digital outputs
- Includes two 32-bit counter/timers
- Reduces ground-loop problems through bank isolation
- Supports PXI timing, triggers and NI-DAQmx
Frequently Asked Questions
What is the PXI-6239?
The PXI-6239 is a bank-isolated PXI current I/O module with eight ±20 mA inputs, two 0–20 mA outputs, six digital inputs, four sinking outputs and two counter/timers.
What is the PXI-6239 part number?
The standard NI part number for the PXI-6239 is 779626-01.
Does the PXI-6239 measure voltage?
No. Its analog inputs are designed for current measurement with a fixed ±20 mA range. The PXI-6233 should be considered when isolated voltage inputs are required.
How many current inputs does the PXI-6239 provide?
It provides eight differential current input channels with 16-bit resolution.
What is the maximum analog input sample rate?
The maximum aggregate sampling rate is 250 kS/s. This rate is shared among the active channels in a multichannel task.
What current can the analog outputs generate?
Each analog output can generate a programmable current from 0 mA to 20 mA.
Do the analog outputs require external power?
Yes. A user-provided 10 VDC to 30 VDC supply is required to drive the analog current-output loops.
What load can the current output drive?
The module can drive a resistive load of up to approximately 1 kΩ when used with a 24 V external supply under the specified conditions.
Are the digital outputs sourcing or sinking?
The four digital outputs are sinking outputs. The PXI-6238 provides the comparable current I/O configuration with sourcing digital outputs.
What is the digital input voltage range?
The six digital inputs accept 0 V to 30 V signals. Logic low is 0 V to 4 V, and logic high is 10 V to 30 V.
Does the PXI-6239 provide channel-to-channel isolation?
No. It uses bank isolation. Channels within a functional bank share a field reference and are not individually isolated from one another.
Which connector does the PXI-6239 use?
The module uses a 37-pin D-Sub front connector compatible with suitable SH37F-37M cables and 37-pin terminal accessories.
Which software controls the PXI-6239?
The PXI-6239 is controlled with NI-DAQmx and can be integrated with LabVIEW, LabWindows/CVI, C/C++ and compatible .NET environments.
Is the PXI-6239 discontinued?
Yes. NI lists the PXI-6239 as discontinued with limited support. Availability may depend on existing inventory or tested secondary-market units.
Request a Quote for the PXI-6239
Contact us for current availability, condition, lead time and project pricing for the PXI-6239 8-Channel Bank-Isolated Current I/O Module. We can also help identify compatible 37-pin cables, high-voltage terminal blocks, PXI chassis and sourcing or sinking current-I/O alternatives.
