RMX-4123 750 W Programmable DC Power Supply
The RMX-4123 is a single-channel, rack-mount programmable DC power supply designed for automated validation, component testing and high-voltage electronic system development. It provides 750 W of output power with rated limits of up to 650 VDC or 3.5 A.
The power supply supports constant-voltage and constant-current operation, front-panel control and remote programming through USB, LAN, RS232 or analog interfaces. Its 1U full-width rack-mount design helps integrate high-voltage DC power into laboratory and automated production systems.
The RMX-4123 is particularly suitable for applications requiring high voltage at moderate current, including power electronics testing, capacitor evaluation, photovoltaic component testing, insulation research and high-voltage device characterization.
RMX-4123 Product Overview
The RMX-4123 uses a flexible voltage-current output architecture rather than limiting users to a single fixed operating point. Voltage and current can be adjusted across a wide range while remaining within the 750 W maximum output-power envelope.
The rated voltage and current limits cannot be delivered simultaneously because 650 V at 3.5 A would exceed 750 W. At higher output voltages, the available current is automatically limited by the maximum power rating; at higher current settings, the available voltage is correspondingly reduced.
Front-panel knobs, buttons and displays support interactive operation. For automated systems, SCPI-compatible commands and multiple communication interfaces allow the power supply to be controlled from LabVIEW, NI-VISA and supported text-based programming environments.
Key Features of the RMX-4123
750 W Output Power
The RMX-4123 provides up to 750 W from a single programmable output. Its wide operating range allows one instrument to support multiple voltage and current combinations within the rated power boundary.
Up to 650 VDC Output
The rated output-voltage range extends from 0 V to 650 VDC. The programmable voltage setting range extends to 682.5 V for control and protection configuration, but normal operation must remain within the documented voltage, power and safety limits.
Up to 3.5 A Output Current
The rated current limit is 3.5 A, with a programmable setting range up to 3.675 A. Current availability depends on the selected voltage and the 750 W maximum output-power limit.
Constant-Voltage and Constant-Current Operation
The power supply automatically operates in constant-voltage or constant-current mode according to the configured limits and connected load. Front-panel indicators show the active operating mode.
- Constant-voltage mode regulates the programmed output voltage
- Constant-current mode limits and regulates output current
- Automatic transition occurs according to the load condition
USB, LAN and RS232 Interfaces
Multiple communication interfaces simplify integration with computers, programmable logic controllers and automated test systems. LAN control is suitable for networked laboratories, while USB and RS232 support direct or legacy system connections.
Analog Control
Analog control connections allow external equipment to adjust or monitor the output without relying entirely on a software communication interface. This is useful for hardware-controlled test stands and systems requiring direct analog feedback.
SCPI-Compatible Programming
SCPI-compatible commands support integration with NI-VISA, LabVIEW and supported text-based languages. Engineers can automate voltage and current sequences, read operating conditions and monitor protection events.
Remote Sensing
Remote-sense connections compensate for voltage drop in the load wiring. The RMX-4123 supports up to 5 V of remote-sense compensation per line, subject to the overall output-voltage and power limits.
Integrated Protection Functions
Protection and limit functions help protect the device under test and the power supply:
- Adjustable overvoltage protection
- Secondary fixed overvoltage protection
- Adjustable overcurrent protection
- Undervoltage limit
- Output power limiting
- Alarm indication and output shutdown
RMX-4123 Technical Specifications
| Product Model | RMX-4123 |
|---|---|
| NI Part Number | 784764-01 |
| Product Type | Programmable DC Power Supply |
| Number of Output Channels | 1 |
| Maximum Output Power | 750 W |
| Rated Output Voltage | 0 V to 650 VDC |
| Voltage Setting Range | 0 V to 682.5 V |
| Rated Output Current | 0 A to 3.5 A |
| Current Setting Range | 0 A to 3.675 A |
| Voltage Setting Accuracy | ±(0.05% of setting + 0.05% of rating) |
| Current Setting Accuracy | ±(0.5% of setting + 0.1% of rating) |
| Voltage Line Regulation | ±67 mV |
| Voltage Load Regulation | ±67 mV |
| Current Line Regulation | ±2.35 mA |
| Current Load Regulation | ±5.7 mA |
| Voltage Ripple and Noise | 330 mV peak-to-peak; 60 mV RMS |
| Current Ripple and Noise | 15 mA RMS |
| Transient Response | 7 ms or less under documented conditions |
| Remote-Sense Compensation | Up to 5 V per line |
| Overvoltage Protection Range | 65 V to 728 V |
| Overcurrent Protection Range | 0.35 A to 3.92 A |
| Operating Modes | Constant voltage and constant current |
| Remote Interfaces | USB, LAN, RS232 and analog control |
| Programming Support | SCPI, NI-VISA and LabVIEW |
| AC Input | 100 VAC to 240 VAC nominal, single phase |
| AC Input Range | 85 VAC to 265 VAC |
| Input Frequency | 47 Hz to 63 Hz |
| Rack Height | 1U |
| Rack Width | Full width |
| Operating Temperature | 0°C to 50°C |
| Recommended Calibration Interval | 1 year |
| Lifecycle Status | Active |
Understanding the 750 W Output Envelope
The RMX-4123 can reach its maximum voltage or maximum current, but not both at the same time. The relationship is limited by the following power equation:
Output power = Output voltage × Output current
For example, the approximate current available at 650 V within a 750 W envelope is 1.15 A. At 3.5 A, the approximate voltage available within the same power envelope is 214 V. Actual operation is also subject to the instrument’s voltage, current and protection limits.
This flexible output characteristic makes the RMX-4123 useful when multiple devices require different combinations of high voltage and moderate current.
How the RMX-4123 Works
The user programs a voltage limit and a current limit from the front panel or a remote interface. The connected load determines whether the power supply operates in constant-voltage or constant-current mode.
When the load draws less than the programmed current limit, the RMX-4123 regulates voltage. If the load attempts to draw more than the current limit, the supply transitions into constant-current operation and reduces voltage as required.
Voltage and current readings can be monitored by the control application, allowing the automated system to verify device behavior and respond to abnormal conditions.
Remote Control and Automation
The RMX-4123 can be integrated into automated test systems using USB, Ethernet LAN or RS232. SCPI commands can be used to configure output levels, activate the output, read measurements and identify protection events.
Typical automated operations include:
- Programmable voltage ramps
- Current-limited device startup
- Power cycling
- Voltage margin testing
- Protection threshold validation
- Long-duration reliability testing
- Remote monitoring and shutdown
Series and Parallel Operation
RMX-412x power supplies can be combined in supported configurations when a test requires voltage or current beyond the rating of one unit. NI documents configurations of up to two compatible supplies in series for increased voltage and up to four in parallel for increased current.
Series or parallel operation requires compatible models, correct control configuration, appropriate wiring and strict compliance with the user manual. High-voltage series systems should be designed and operated only by qualified personnel.
Typical Applications
- High-voltage component characterization
- Power semiconductor testing
- Capacitor and insulation testing
- Photovoltaic component development
- Automotive and aerospace electronics validation
- Industrial power electronics testing
- DC-DC converter input testing
- High-voltage sensor and actuator testing
- Research and laboratory power systems
- Automated production testing
- Reliability and burn-in testing
Safety and Installation Considerations
The RMX-4123 can generate hazardous voltages. Installation and operation should be performed by personnel trained in high-voltage electrical safety.
- Use wiring and connectors rated for the maximum voltage and current
- Provide suitable insulation, guarding and strain relief
- Use an emergency shutdown or interlock where required
- Confirm that the output is discharged before touching the terminals
- Keep adequate space for ventilation and rack airflow
- Verify protective earth and grounding before operation
- Do not exceed the 750 W output-power envelope
The RMX-4123 supports positive or negative output grounding within documented limits. NI specifies that the output should not be grounded when generating more than 600 V. Review the user manual before configuring the grounding arrangement.
Calibration and Maintenance
NI recommends a one-year calibration interval for the RMX-412x power supply family. A calibration software utility can be used with a suitable digital multimeter to perform supported calibration procedures.
Calibration history, environmental conditions and application requirements should be considered when establishing the final calibration schedule for a production or regulated test system.
RMX-4123 Troubleshooting
Output Voltage Does Not Reach the Programmed Level
Check whether the power supply has entered constant-current mode or reached the 750 W power limit. Inspect the connected load, current setting and remote-sense wiring.
Output Turns Off and Displays an Alarm
Review the displayed alarm code and check the overvoltage, overcurrent and protection settings. Confirm that the load is not shorted and that voltage transients are within the configured limits.
Voltage at the Load Is Lower Than the Displayed Value
Voltage drop may be occurring in the load cables. Use correctly connected remote-sense leads and adequately sized power wiring. Remote-sense compensation cannot exceed the documented limit.
Remote Communication Does Not Work
Verify the selected USB, LAN or RS232 interface settings. For LAN operation, confirm the IP address and network configuration; for RS232, check the baud rate and cable type.
Output Remains Energized Longer Than Expected
High-voltage output capacitors may require time to discharge, especially when the output is lightly loaded. Always verify the actual terminal voltage before servicing or changing connections.
RMX-4123 vs RMX-4122
The RMX-4122 is another 750 W model with a lower maximum voltage and higher current capability. It provides up to 230 V and 10 A, while the RMX-4123 provides up to 650 V and 3.5 A.
Choose the RMX-4122 for medium-voltage applications requiring more current. Choose the RMX-4123 when the test requires voltage above 230 V.
RMX-4123 vs RMX-4127
The RMX-4127 provides the same 650 V maximum voltage class but increases rated power to 1,500 W and rated current to 7 A.
The RMX-4123 is more appropriate when 750 W is sufficient and lower AC input power is preferred. The RMX-4127 is better suited to high-voltage applications requiring greater current or output power.
RMX Programmable Power Supply Comparison
| Model | Maximum Power | Maximum Voltage | Maximum Current | Best Suited For |
|---|---|---|---|---|
| RMX-4120 | 750 W | 30 V | 75 A | Low-voltage, high-current testing |
| RMX-4121 | 750 W | 80 V | 28 A | General power electronics |
| RMX-4122 | 750 W | 230 V | 10 A | Medium-voltage testing |
| RMX-4123 | 750 W | 650 V | 3.5 A | High-voltage testing |
| RMX-4127 | 1,500 W | 650 V | 7 A | Higher-power, high-voltage testing |
How to Select the Right Power Supply
Choose the RMX-4123 when the application requires:
- DC output voltages above 230 V
- Up to 750 W of programmable power
- Current no higher than 3.5 A
- Constant-voltage and constant-current operation
- USB, LAN, RS232 or analog control
- 1U full-width rack integration
Consider another model when the application requires more current, more than 750 W, multiple independent outputs or substantially lower voltage with improved low-level resolution.
Recommended Related Products
- RMX-4122 Programmable Power Supply – 750 W model providing up to 230 V and 10 A.
- RMX-4127 Programmable Power Supply – 1,500 W high-voltage model providing up to 650 V and 7 A.
- RMX-4121 Programmable Power Supply – 750 W option for applications requiring up to 80 V and 28 A.
- RMX-4120 Programmable Power Supply – Low-voltage, high-current 750 W model providing up to 30 V and 75 A.
- PXIe-4081 Digital Multimeter – Precision measurement module for monitoring voltage, current and resistance in automated systems.
Why Choose the RMX-4123?
- 750 W programmable DC output
- Voltage capability up to 650 VDC
- Current capability up to 3.5 A
- Constant-voltage and constant-current modes
- USB, LAN, RS232 and analog control
- SCPI-compatible automation
- Remote-sense connections
- Integrated voltage and current protection
- Compact 1U rack-mount format
- Active NI lifecycle status
Frequently Asked Questions
What is the RMX-4123 used for?
The RMX-4123 supplies programmable high-voltage DC power for electronic validation, power semiconductor testing, component characterization, reliability testing and automated production systems.
What is the maximum output voltage?
The rated maximum output voltage is 650 VDC. The voltage setting range extends to 682.5 V for supported configuration and protection functions.
What is the maximum output current?
The rated maximum output current is 3.5 A, subject to the 750 W output-power limit.
Can it supply 650 V and 3.5 A simultaneously?
No. That operating point would exceed the 750 W rating. Voltage and current combinations must remain within the maximum output-power envelope.
Does the RMX-4123 support constant-current operation?
Yes. It automatically transitions between constant-voltage and constant-current operation according to the load and programmed limits.
Which remote-control interfaces are available?
The RMX-4123 supports USB, LAN, RS232 and analog control interfaces.
Does it support remote sensing?
Yes. Remote sensing can compensate for load-wire voltage drop, with up to 5 V of compensation per sense line.
Can multiple RMX power supplies be combined?
Supported RMX-412x configurations can use up to two compatible units in series or up to four in parallel. Follow the NI user manual and all high-voltage safety requirements.
What is the recommended calibration interval?
NI recommends a one-year calibration interval.
What is the NI part number for the RMX-4123?
The standard orderable NI part number is 784764-01.
What is included with the RMX-4123?
NI lists the programmable power supply and its safety, environmental and regulatory documentation as included items. Verify power cord, rack hardware and software requirements when ordering.
Request a Quote for the RMX-4123
Contact us for current availability, lead time and project pricing for the RMX-4123 750 W Programmable DC Power Supply. We can also help compare RMX power supply models and verify the required voltage, current, rack and communication configuration.
