RMX-4120 750 W 30 V 75 A Programmable DC Power Supply
Земля RMX-4120 is a single-channel, 750 W programmable DC power supply designed for automated validation, production testing, power-electronics development and high-current laboratory applications. Its autoranging output architecture provides flexible voltage and current combinations within the 750 W power envelope, with rated output capability up to 30 VDC or 75 A.
The RMX-4120 occupies only 1U of full-width rack space and supports both local and automated operation. Front-panel controls allow engineers to configure and monitor the supply directly, while LAN, USB, RS232 and analog interfaces provide flexible integration with computers, industrial controllers and automated test systems.
Key Features of the RMX-4120
- 750 W maximum output power
- 30 V rated output voltage
- 75 A rated output current
- Autoranging output architecture
- 0 V to 31.5 V programmable voltage range
- 0 A to 78.75 A programmable current range
- Single programmable DC output channel
- Constant-voltage and constant-current operation
- Four-wire remote sensing
- Up to 1.5 V remote-sense compensation per line
- 1 ms or less voltage transient response
- Programmable overvoltage and overcurrent protection
- Undervoltage limit protection
- Three front-panel preset memories
- LAN, USB and RS232 communication
- External analog programming and monitoring
- Parallel operation with up to four identical units
- Series operation with up to two identical units
- Compact 1U full-width rack-mount design
RMX-4120 Technical Specifications
| Product Model | RMX-4120 |
|---|---|
| Part Number | 784761-01 |
| Product Type | Programmable rack-mount DC power supply |
| Number of Output Channels | 1 |
| Rated Output Power | 750 W |
| Rated Output Voltage | 30 VDC |
| Rated Output Current | 75 A |
| Voltage Setting Range | 0 V to 31.5 V |
| Current Setting Range | 0 A to 78.75 A |
| Voltage Setting Accuracy | ±(0.05% of setting + 0.05% of rated voltage) |
| Current Setting Accuracy | ±(0.5% of setting + 0.1% of rated current) |
| Voltage Line Regulation | ±5 mV |
| Voltage Load Regulation | ±5 mV |
| Current Line Regulation | ±9.5 mA |
| Current Load Regulation | ±20 мА |
| Voltage Transient Response | 1 ms or less under specified load-change conditions |
| Voltage Ripple and Noise | 60 mV peak-to-peak; 8 mV RMS |
| Current Ripple and Noise | 150 mA RMS under specified conditions |
| Voltage Rise Time | 100 ms |
| Voltage Fall Time | 100 ms at rated load; 550 ms at no load with bleeder enabled |
| Remote-Sense Compensation | Up to 1.5 V per load line |
| Overvoltage Protection Range | 3 V to 33.6 V |
| Fixed Secondary Overvoltage Protection | 36 V |
| Overcurrent Protection Range | 7.5 A to 84 A |
| AC Input Rating | 100 VAC to 240 VAC, 50 Hz to 60 Hz, single phase |
| AC Input Voltage Range | 85 VAC to 265 VAC |
| Maximum AC Input Power | 1,100 VA at 100 VAC |
| LAN Interface | 10Base-T or 100Base-TX Ethernet, IPv4 |
| Other Interfaces | USB, RS232 and analog control |
| Parallel Operation | Up to four identical RMX-4120 units including the master |
| Series Operation | Up to two identical RMX-4120 units |
| Preset Memory | Three settings |
| Rack Size | 1U, full rack width |
| Weight | Approximately 8 kg |
| Охлаждение | Forced-air fan cooling |
| Operating Temperature | 0°C to 50°C |
| Operating Humidity | 20% to 85% RH, noncondensing |
| Maximum Altitude | 2,000 m |
RMX-4120 Part Number and Included Items
| Item | Part Number | Описание |
|---|---|---|
| RMX-4120 | 784761-01 | 750 W, 30 V, 75 A single-channel programmable DC power supply |
| Power Supply | Included | One RMX-4120 rack-mount power supply |
| Output Terminal Hardware | Included with applicable configuration | Hardware and cover for connecting high-current output cables |
| Safety Documentation | Included | Safety, environmental and regulatory documentation |
Because the RMX-4120 can supply as much as 75 A, output cables, crimp terminals, protective devices and fixture connections must be selected for the maximum expected continuous current. Verify the required AC power cord and regional plug configuration before ordering.
750 W Autoranging Output Architecture
The RMX-4120 operates across a broad combination of voltage and current values within its 750 W maximum power envelope. Unlike a supply that can deliver its rated voltage and rated current simultaneously, the RMX-4120 limits available voltage or current whenever their product would exceed 750 W.
For example, the supply can approach its 75 A rating at lower voltage, while operation near 30 V reduces the maximum available current to approximately 25 A. Engineers should calculate the required operating point rather than assuming that 30 V and 75 A are available simultaneously.
30 V Rated Output Voltage
The RMX-4120 has a rated output voltage of 30 V and a programmable setting range extending to 31.5 V. This range supports common 12 V, 24 V and 28 V electronic systems while providing additional adjustment headroom.
Applications include automotive electronics, industrial controllers, telecommunications equipment, computing hardware, power converters and other low-voltage devices requiring substantial input power.
75 A Rated Output Current
The rated current of 75 A makes the RMX-4120 suitable for high-current DUTs that cannot be powered by conventional benchtop supplies. Its programmable current range extends to 78.75 A for setting and protection purposes.
At high current, cable resistance can create significant voltage drop and heat. Use short, low-resistance conductors, correctly sized crimp terminals and properly tightened output connections.
Constant-Voltage Operation
In constant-voltage mode, the RMX-4120 regulates the programmed voltage while allowing the DUT to draw current up to the configured current setting. The front-panel CV indicator shows when the supply is regulating voltage normally.
If the load requires more current than the programmed setting permits, the supply transitions into constant-current operation. This behavior helps limit DUT current during startup, overload or short-circuit conditions.
Constant-Current Operation
In constant-current mode, the RMX-4120 regulates output current while the voltage changes according to the connected load. The CC indicator shows when current regulation is active.
Constant-current operation is useful for LED assemblies, component conditioning, battery-related testing and devices requiring controlled current. The voltage setting acts as the maximum permitted output voltage.
Four-Wire Remote Sensing
The RMX-4120 supports remote sensing to compensate for voltage drop between the power supply and the DUT. Separate sense leads measure voltage directly at the load, allowing the supply to increase its terminal voltage until the programmed voltage reaches the DUT.
The supply can compensate for up to 1.5 V of drop on each load line. The total output remains subject to the maximum terminal voltage and 750 W power limit.
Use twisted-pair or shielded sense wiring and connect the sense terminals with the correct polarity. High-current output cables must still be sized to prevent excessive voltage drop and heating.
Fast Transient Response
The RMX-4120 provides a voltage transient-response time of 1 ms or less under the specified load-change conditions. This helps the output recover quickly when the DUT changes between operating states.
Actual behavior depends on load characteristics, output cables, remote-sense wiring and external capacitance. Dynamic loads should be evaluated using the intended production fixture and cable arrangement.
Low Voltage Line and Load Regulation
Voltage line regulation and load regulation are specified at ±5 mV. These characteristics help the RMX-4120 maintain a stable output when the AC input or connected load changes.
For accurate regulation at the DUT, combine stable supply operation with remote sensing, low-resistance output wiring and properly separated sense conductors.
Programmable Overvoltage Protection
The overvoltage protection threshold can be set from 3 V to 33.6 V. When the output exceeds the configured threshold, the RMX-4120 turns off its output, displays an OVP message and activates the alarm indicator.
A secondary fixed protection threshold is set at 36 V, equivalent to 120% of the rated output voltage. Configure the primary OVP setting according to the maximum safe voltage of the connected DUT.
Programmable Overcurrent Protection
The overcurrent protection threshold can be configured from 7.5 A to 84 A. When the protection condition is detected, the supply disables its output and displays the applicable alarm.
OCP should be configured independently from the normal constant-current setting. The constant-current setting regulates normal operation, while OCP is intended to shut down the output when an abnormal current condition occurs.
Undervoltage Limit
The programmable undervoltage limit prevents operators or software from setting the output below a defined voltage. This can protect devices that must not be operated below a minimum supply level.
The RMX-4120 undervoltage-limit setting range extends from 0 V to 31.5 V. Use this function when an incorrect low-voltage setting could create excessive current or unstable DUT operation.
Three Preset Memories
The RMX-4120 can store as many as three groups of commonly used settings. Each preset can include voltage, current, OVP, OCP and undervoltage-limit values.
Preset memory reduces setup time when operators repeatedly test several known products or operating conditions. The front-panel indicators identify the active preset.
LAN Remote Control
The Ethernet interface supports 10Base-T and 100Base-TX communication over IPv4 networks. LAN control is suitable for production racks, shared laboratories and systems in which the power supply is located away from the computer.
Configure the instrument IP address, subnet parameters and communication settings before opening the software connection. Network security settings must permit communication between the controller and instrument.
USB Connectivity
USB provides a direct connection for benchtop development and automated systems with a nearby control computer. Install the required driver and communication software before connecting the instrument.
If the computer does not recognize the supply, check the USB cable, port, device driver and VISA configuration. A direct connection is preferable during initial troubleshooting.
RS232 Serial Communication
The RS232 interface supports integration with industrial computers, legacy test stations and embedded controllers. Serial communication can be useful when USB or Ethernet is not available.
The computer and RMX-4120 must use matching serial settings, including baud rate, data format and command termination.
External Analog Control
The analog-control interface allows an external voltage or resistance to control the RMX-4120 output. Analog monitoring signals can also represent operating voltage, current and status for use by an external controller.
This interface is useful for real-time control systems, hardware-in-the-loop applications and installations that require fast control without sending individual software commands.
Parallel Operation
As many as four identical RMX-4120 supplies, including the master unit, can be configured for master-slave parallel operation. Parallel operation increases the total available output current and power.
Only identical models should be combined. All output cables, current-sharing connections, protective devices and AC circuits must be designed for the total system capacity.
Series Operation
Up to two identical RMX-4120 supplies can be operated in series when the application requires increased voltage. Series operation remains subject to the instrument’s output-to-ground isolation limits.
Review grounding, floating-voltage and remote-sensing requirements before connecting supplies in series. Do not exceed the permitted isolation voltage or safety limits.
Typical RMX-4120 Applications
- Automotive electronics testing
- Electric-vehicle component validation
- DC-DC converter testing
- Power electronics development
- Industrial controller testing
- Telecommunications equipment validation
- Computer and server hardware testing
- LED and lighting-system testing
- Battery-powered device simulation
- High-current component testing
- Production functional testing
- Burn-in and reliability testing
- Research and laboratory automation
- Rack-mounted automated test equipment
Automotive Electronics Testing
The RMX-4120 can supply power to 12 V, 24 V and 28 V automotive electronic systems. Engineers can program different voltage levels and current limits to evaluate controllers, lighting assemblies, infotainment equipment and other vehicle electronics.
Fast transient waveforms such as standardized automotive surges may require dedicated transient-generation equipment. Verify waveform requirements before using the RMX-4120 as the only source.
DC-DC Converter Testing
The autoranging output can power DC-DC converters across different input-voltage and load-power conditions. Test software can change the supply voltage and monitor the converter using digital multimeters, oscilloscopes and electronic loads.
Remote sensing is especially useful for high-current converter testing because it compensates for voltage lost in the source cables.
Computer and Server Hardware Testing
The 75 A current capability supports low-voltage computing devices, server assemblies and communication hardware with substantial power requirements. Controlled current limiting can protect prototype boards during initial power-up.
Before enabling the output, verify polarity, current limits and expected inrush current. Large input capacitors may cause the supply to enter current regulation temporarily during startup.
Burn-In and Reliability Testing
The RMX-4120 can continuously power devices during environmental, lifetime and burn-in tests. Remote communication allows voltage, current, power and alarm status to be monitored by automated software.
For long-duration high-power operation, maintain adequate rack airflow and ensure that facility power, cables and fixture terminals are rated for the expected continuous load.
Calibration and Measurement Confidence
The RMX-4120 ships with a calibration utility for maintaining its voltage and current performance. Allow the recommended 30-minute warm-up with current flowing before performing precision verification or calibration.
The applicable calibration interval should be selected according to NI recommendations, the organization’s quality procedures, usage level and required measurement uncertainty.
RMX-4120 Troubleshooting
The RMX-4120 cannot output 30 V at 75 A
The voltage and current ratings cannot be delivered simultaneously because that operating point would exceed 750 W. At 30 V, the maximum current is approximately 25 A. At 75 A, the voltage must remain near or below 10 V.
The output voltage is lower than programmed
Check whether the supply is operating in constant-current mode or has reached its 750 W power limit. Inspect the output cables and use remote sensing when cable voltage drop is significant.
The power-limit indicator is active
The requested voltage and current combination exceeds 750 W. Reduce the output voltage, reduce the required current or use multiple supplies in an approved configuration.
The output cables become hot
Stop the test and inspect the conductor size, crimp terminals, cable length and terminal tightness. High-resistance connections can generate substantial heat at currents approaching 75 A.
The output is unstable with remote sensing
Verify sense-wire polarity and routing. Use twisted-pair or shielded sense wires and consider placing a suitable electrolytic capacitor across the DUT when permitted by the application.
The supply reports an OVP alarm
Confirm that the OVP threshold is above the intended operating voltage but below the DUT’s maximum safe voltage. Inspect remote-sense wiring and external sources that may be driving voltage back into the output.
The supply reports an OCP alarm
Check the DUT for a short circuit, excessive inrush current or an incorrectly programmed threshold. OCP is a shutdown function and is separate from normal constant-current regulation.
The LAN connection does not work
Confirm the IP address, subnet mask and physical network connection. Verify that the computer can reach the instrument and that firewall or network-security settings are not blocking communication.
The USB connection is not detected
Check the USB cable, computer port and installed communication drivers. Connect the supply directly to the computer during troubleshooting and verify its VISA resource.
The unit shuts down during continuous testing
Check the alarm message, rack airflow, fan operation, AC input and ambient temperature. Make sure the front and rear ventilation openings are not obstructed.
RMX-4120 Comparison with Similar Programmable Power Supplies
| Модель | Rated Output | Power | Best Suited For |
|---|---|---|---|
| RMX-4120 | 30 V, 75 A | 750 W | Low-voltage, high-current device testing |
| RMX-4121 | 80 V, 28 A | 750 W | Medium-voltage power-electronics testing |
| RMX-4122 | 230 V, 10 A | 750 W | Higher-voltage converters and industrial devices |
| RMX-4123 | 650 V, 3.5 A | 750 W | High-voltage semiconductor and power-system testing |
| RMX-4124 | Low-voltage, high-current output | 1,500 W | Applications requiring more current and power than the RMX-4120 |
| RMX-4104 | Up to 100 V or 40 A, depending on version | Up to 864 W | Fixed-range high-power rack systems |
RMX-4120 vs RMX-4121
The RMX-4120 and RMX-4121 both provide 750 W, but their voltage and current ranges are different. The RMX-4120 supports up to 30 V and 75 A, while the RMX-4121 supports higher voltage up to 80 V and lower maximum current.
Select the RMX-4120 for low-voltage, high-current devices. Select the RMX-4121 when the application requires voltage above 30 V.
RMX-4120 vs RMX-4124
The RMX-4124 belongs to the 1,500 W class and provides approximately twice the power of the RMX-4120. It is intended for applications requiring higher current or greater total power.
Select the RMX-4120 when 750 W is sufficient and standard 1U system density is important. Select the RMX-4124 when the DUT’s operating point exceeds the RMX-4120 power envelope.
RMX-4120 vs RMX-4104
Земля RMX-4104 is available in several fixed voltage and current configurations with output power up to 864 W. The RMX-4120 provides a wider autoranging operating area within a 750 W envelope and reaches a higher maximum current of 75 A.
Choose the RMX-4120 for flexible low-voltage, high-current testing. Choose the RMX-4104 when one of its fixed 20 V, 36 V, 60 V or 100 V configurations more closely matches the application.
Recommended Related Products
- RMX-4121 750 W Programmable DC Power Supply
- RMX-4122 750 W High-Voltage DC Power Supply
- RMX-4123 650 V Programmable DC Power Supply
- RMX-4124 1,500 W Programmable DC Power Supply
- RMX-4104 High-Power Programmable DC Power Supply
- PXI-4130 40 W Source Measure Unit
- View More NI PXI and PXI Express Modules
Selecting the Right RMX Programmable Power Supply
Choose the RMX-4120 when the application requires up to 75 A, operates at 30 V or below and remains within a 750 W power envelope. Its autoranging output is especially useful when one test system must support several voltage and current combinations.
Select the RMX-4121, RMX-4122 or RMX-4123 when higher voltage is required. Consider the 1,500 W RMX-4124 series when the required power exceeds 750 W.
Why Choose the RMX-4120?
- Provides up to 750 W from one programmable channel
- Supports current up to 75 A
- Supports voltage up to 30 VDC
- Offers flexible autoranging operation
- Compensates cable drop through remote sensing
- Includes programmable OVP, OCP and UVL protection
- Supports LAN, USB, RS232 and analog control
- Supports series and parallel multidevice operation
- Stores three front-panel preset configurations
- Occupies only 1U of rack height
Frequently Asked Questions
What is the RMX-4120?
The RMX-4120 is a single-channel, 750 W autoranging programmable DC power supply with rated output capability up to 30 V or 75 A.
Can the RMX-4120 output 30 V and 75 A simultaneously?
No. That operating point would require 2,250 W. The RMX-4120 limits voltage and current combinations to a maximum output power of 750 W.
What is the programmable voltage range?
The voltage setting range is 0 V to 31.5 V. The rated output voltage is 30 V.
What is the programmable current range?
The current setting range is 0 A to 78.75 A. The rated output current is 75 A.
Does the RMX-4120 support remote sensing?
Yes. Its remote-sense terminals can compensate for as much as 1.5 V of voltage drop on each output line.
Can multiple RMX-4120 supplies be connected in parallel?
Yes. Up to four identical RMX-4120 units, including the master, can be used in a supported master-slave parallel configuration.
Can RMX-4120 units be connected in series?
Yes. Up to two identical units can be used in a supported series configuration, subject to grounding and isolation requirements.
Which communication interfaces are available?
The RMX-4120 supports LAN, USB, RS232 and external analog control.
Does the RMX-4120 include protection functions?
Yes. It provides programmable overvoltage protection, secondary fixed overvoltage protection, overcurrent protection, an undervoltage limit and thermal protection.
What is the RMX-4120 part number?
The standard NI part number for the RMX-4120 is 784761-01.
Request a Quote for the RMX-4120
Contact us for current availability, lead time and project pricing for the RMX-4120 750 W 30 V 75 A Programmable DC Power Supply. We can also help identify compatible AC power cords, high-current output cables, rack accessories and related RMX power supplies for your automated test system.
