DC electronic loads for a low-voltage bench: SIGLENT vs RIGOL

Give the power supply a job before you give it an ESP32. A DC electronic load draws a current you choose, so you can inspect a supply’s output without using your sensor board as the test load. Choose SIGLENT SDL1020X-E for a LAN-ready bench, or RIGOL DL3021 for a higher current ceiling within the same 200 W power envelope.

Sources: research-based picks from the makers’ datasheets and manuals, checked November 1, 2026.

The supply feeds; the load consumes

A bench supply delivers power. An electronic load sinks it. In constant-current mode, you choose the current draw and watch the voltage and power readback as the source supplies that load.

That is a different job from the multimeter on your first electronics bench or a plug-in AC power meter. The meter observes; the electronic load gives the DC source a controlled demand.

Start with a low-voltage, current-limited bench supply with accessible DC terminals. The exercise below uses small steady loads; leave battery discharge and high-voltage testing out of this first session.

Two picks, with the limits kept together

Pick	Maker input limits	Minimum-voltage point stated by maker	Control connections	Fit
SIGLENT SDL1020X-E	150 V, 30 A, 200 W	0.15 V at 5 A; 0.9 V at 30 A	Built-in RS232, USB and LAN	A LAN-ready programmable bench
RIGOL DL3021	150 V, 40 A, 200 W	1 V at 40 A	USB host/device, RS232; LAN optional	More rated current within 200 W

The SIGLENT datasheet identifies SDL1020X-E as the 200 W model with built-in communication interfaces. Choose it if LAN control is part of your plan from the start.

The RIGOL datasheet gives DL3021 the higher current ceiling, but its detailed interface table marks LAN as optional. Its dynamic-mode maximum is 15 kHz; the DL3021A is a different model.

Voltage, current and power limits apply together. The minimum-voltage figures are operating points at the stated currents, not universal turn-on thresholds. Choose for the complete operating envelope, rather than collecting the largest number in each column.

Learn CC first; keep the other modes in reach

Both loads offer these steady-state modes:

• CC — constant current: draw the current you set, within the load’s operating capability.
• CV — constant voltage: adjust the current drawn to hold the terminal voltage at the setpoint.
• CR — constant resistance: behave like the selected resistance.
• CP — constant power: adjust the current draw to dissipate the selected power.

Use CC for the first session. It gives you an easy question: what voltage does the source deliver at this current? The SIGLENT manual explains the mode controls, ranges and readback.

A small first session: 5 V, two current settings

Assume a 5 V bench supply and leads rated for both chosen current settings. These are hypothetical setpoints with calculated power, not measured results:

Assumed source voltage	CC setpoint	Calculated power, V × I
5 V	0.1 A	0.5 W
5 V	0.5 A	2.5 W

The arithmetic is straightforward:

5 V × 0.1 A = 0.5 W
5 V × 0.5 A = 2.5 W

Record the actual readback separately. If the source voltage changes, the actual power changes with it.

Connect, set, enable, record

Keep the instruments’ protective earth connected and their ventilation clear. With the source off and load input disabled, connect source positive to load positive and negative to negative using appropriately rated leads; check polarity before enabling either device. Follow the maker terminal diagrams, including the RIGOL connection guidance.

For the SIGLENT first session:

1. Set the source to the assumed voltage and a suitable current limit within its rating, allowing for the intended load.
2. Press CC. Select the lower current and voltage ranges appropriate to this exercise; the manual lists 5 A and 36 V ranges.
3. Set the current to 0.1 A, restore source output, then press On/Off to enable the load input.
4. Record displayed voltage, current and power. Disable the load input before selecting the 0.5 A setpoint, then enable it and record again.
5. Disable the load input and turn off source output before disconnecting.

If the source behaves unexpectedly or cannot maintain the intended operating point, stop and inspect the settings and connections. Do not keep increasing the demand to chase a target reading.

Know where the voltage is being read

Connection leads can introduce voltage drop. Both makers document remote-sense connections for measuring at the source terminals rather than relying only on the load-terminal voltage. Follow the separate sense-terminal diagram when you use that feature.

For your first small exercise, keep the setup simple and write down where you measured. When you change leads or add sense connections later, you can compare like with like.

Save a test you can repeat

Keep the source voltage and current-limit settings, load mode and setpoints, lead arrangement and actual readbacks together. A short record makes the next comparison useful: same setup, same demand, another source or cable.

Choose the SIGLENT for documented built-in LAN, or the RIGOL for its higher current ceiling. Then start small. A controlled demand and a clear record tell you more than making the biggest wattage number appear on screen.