Overview
Array instruments expose a TTL-level serial port. The 3311 translates PC RS-232C to TTL, ensuring correct logic levels and robust communication for scripting, automation and data logging.
Where It Fits
- 3644A/3645A/3646A Array 364X PSU series
- 3710A/3711A/3715A Array 371X DC loads
Why It Matters
| Feature | Why It’s Important | What You Gain |
|---|---|---|
| Correct Level Translation | RS-232C uses bipolar signalling; Array ports expect TTL. | Reliable framing, fewer comms errors, safe operation. |
| Array-Specific Pin-Out | Matches instrument wiring and addressing conventions. | Drop-in setup; no custom harnesses. |
| Binary Command Frames | Simple 26-byte frames for control and readback. | Deterministic timing and easy parsing. |
| DB9 Connectivity | Standard cabling with strain relief. | Good EMI immunity and serviceability. |
Choosing Alternatives in the Series
For multi-drop or long runs, use 3313 (RS-232↔RS-485) with 3314 (RS-485↔TTL). For GPIB racks, see 3315.
Competitive Landscape
| Type | Example | Notes | When To Prefer 3311 |
|---|---|---|---|
| Brand-specific RS-232↔TTL | Array 3311 | Matches Array manuals and pin-outs. | Controlling 364X/371X without rewiring. |
| Generic RS-232↔TTL | MAX32xx-based converters | May need custom wiring; variable quality. | When you need guaranteed Array compatibility. |
| Other brand adapters | e.g., Maynuo, B&K kits | Sometimes isolated; different pin-outs. | Use 3311 unless isolation or other brand required. |
Getting Started
- Set instrument address and baud (e.g., 9600 8-N-1) via the instrument menu.
- Use a straight-through DB9 RS-232 cable PC ⇄ 3311. The 3311 connects to the instrument’s TTL-level port.
- Send a status query frame to confirm communication, then enable remote control and output/load as needed.
Wiring Quick-Start (364X & 371X)
Minimum Signals You Need
| PC (DB9 DTE) | Signal Direction | Through 3311 | Instrument Port (TTL) | Notes |
|---|---|---|---|---|
| Pin 3 (TXD) | PC → Instrument | Level-shifted | RXD (TTL) | Transmit from PC arrives at instrument RXD. |
| Pin 2 (RXD) | Instrument → PC | Level-shifted | TXD (TTL) | Instrument TXD returns to PC RXD. |
| Pin 5 (GND) | Common | — | GND | Shared reference; keep cables short and shielded. |
RTS/DTR hardware flow control is not used by these models; leave it disabled in software. If you get no replies, swap to a null-modem RS-232 cable only on the PC⇄3311 leg and retest.
Serial Defaults (Factory)
| Model Family | Baud | Data | Parity | Stop | Address Range |
|---|---|---|---|---|---|
| 364X Power Supplies | 9600 (menu-selectable 4800–38400) | 8 | None | 1 | 0–31 |
| 371X Electronic Loads | 9600 | 8 | None | 1 | 0–254 |
Command Frames & Code Snippets
These models use a simple 26-byte binary frame (header 0xAA, address, command, payload, checksum). Checksum is the unsigned sum of bytes 1–25 (mod 256). Below are safe “first actions” you can send to verify comms and toggle control.
364X Power Supplies — Read Status & Enable Output
- Query status: Command 0x81 (26-byte frame). Returns V, I, P and flags.
- Set control: Command 0x82 with Byte4 bits: b1=1 Remote, b0=1 Output ON.
To set limits and a voltage setpoint, use command 0x80 (max current, max voltage, max power, Vset). Start by reading status first to confirm framing and checksum handling.
371X Electronic Loads — Read Status & Turn Load On
- Query status: Command 0x91 (returns I, V, P and limit fields).
- Set control: Command 0x92 with Byte4 bits: b1=1 Remote, b0=1 Load ON.
Typical Troubleshooting
- No response: Confirm baud, address, straight-through cable on PC⇄3311, and shared GND. Try a different COM port.
- Framing errors: Replace cable with shielded DB9; keep total run short; ensure only one level shifter (the 3311) is in the path.
- Wrong instrument responds: Each unit has an address; set unique addresses via the front panel.
Why This Helps You Ship Faster
With the 3311 handling level translation and the example frames above, you can verify communications in minutes, then wrap higher-level control in your preferred language or NI-VISA workflow for regression tests, sweeps and long-duration logging.