HP 34401A — 6½-digit Multimeter¶
Overview¶
The HP 34401A (also marketed as Agilent 34401A and Keysight 34401A) is a classic 6½-digit bench multimeter capable of DC/AC voltage and current, resistance, frequency, period, diode, and continuity measurements.
| Specification | Value |
|---|---|
| Type | 6½-digit DMM |
| Interface | GPIB, USB-TMC, RS-232 |
| SCPI command set | Yes |
| Driver name | HP34401A |
| Resource patterns | GPIB?*::?*::INSTR, USB?*::?*::INSTR, ASRL?*::INSTR |
Connecting¶
- Connect the instrument via GPIB, USB, or RS-232
- Click Add Instrument in the sidebar
- The Connection Manager scans and lists the resource (e.g.
GPIB0::1::INSTR) - Select the resource — the
*IDN?response is parsed and the HP34401A driver is highlighted automatically - Click Connect
Front Panel¶
The HP34401A front panel provides:
| Control | Description |
|---|---|
| DCV button | Measure DC voltage |
| ACV button | Measure AC voltage (true RMS) |
| DCI button | Measure DC current |
| ACI button | Measure AC current |
| Ω 2W button | Measure resistance (2-wire) |
| Ω 4W button | Measure resistance (4-wire, Kelvin) |
| Freq button | Measure frequency |
| Period button | Measure period |
| Diode button | Diode forward voltage |
| Cont button | Continuity (beeps if below threshold) |
| Range drop-down | Auto or fixed range |
| Reading display | Shows last measured value |
| Continuous toggle | Auto-repeat measurements every second |
Sequence Blocks¶
All HP34401A blocks share a common set of properties:
| Property | Type | Description |
|---|---|---|
| Instrument | InstrumentSelector | The connected HP34401A instance to use |
| Range | Number | Measurement range (0 = Auto) |
| Variable Name | Variable | Variable that receives the measured value |
HP34401A_MeasureDCV¶
Sends CONF:VOLT:DC {range},DEF then READ?.
Returns voltage in V.
HP34401A_MeasureACV¶
Sends CONF:VOLT:AC {range},DEF then READ?.
Returns RMS AC voltage in V.
HP34401A_MeasureDCI¶
Sends CONF:CURR:DC {range},DEF then READ?.
Returns current in A.
HP34401A_MeasureACI¶
Sends CONF:CURR:AC {range},DEF then READ?.
Returns RMS AC current in A.
HP34401A_MeasureResistance2W¶
Sends CONF:RES {range},DEF then READ?.
Returns resistance in Ω.
HP34401A_MeasureResistance4W¶
Sends CONF:FRES {range},DEF then READ?.
Returns resistance in Ω. Use 4-wire for low-resistance measurements to eliminate lead resistance.
HP34401A_MeasureFrequency¶
Sends CONF:FREQ {range},DEF then READ?.
Returns frequency in Hz.
HP34401A_MeasurePeriod¶
Sends CONF:PER {range},DEF then READ?.
Returns period in s.
Example Sequence — DC Voltage Log¶
[Start]
→ [Loop N=60, counter=i]
↓ body
[HP34401A_MeasureDCV, Range=10, Variable=voltage]
→ [AddToChart, Series="Battery Voltage", Variable=voltage]
→ [Wait 1000ms]
→ [SaveCsv, Path="C:\Data\battery_test.csv"]
→ [End]
This sequence measures DC voltage once per second for 60 seconds and saves the results to a CSV file.
SCPI Command Reference¶
The driver uses the following SCPI commands:
| Action | Command |
|---|---|
| Configure DCV | CONF:VOLT:DC {range},DEF |
| Configure ACV | CONF:VOLT:AC {range},DEF |
| Configure DCI | CONF:CURR:DC {range},DEF |
| Configure ACI | CONF:CURR:AC {range},DEF |
| Configure Resistance 2W | CONF:RES {range},DEF |
| Configure Resistance 4W | CONF:FRES {range},DEF |
| Configure Frequency | CONF:FREQ {range},DEF |
| Configure Period | CONF:PER {range},DEF |
| Trigger and read | READ? |
| Identification | *IDN? |
| Reset | *RST |