Command reference - B&K 2831E and DAQ3120

COMMAND REFERENCE - B&K 2831E and B&K DAQ3120 ONLY
Extract of the project's command_register.md, sections 0-3.
The oscilloscope and power-supply sections are DELIBERATELY EXCLUDED: those
instruments are out of scope for the discovery tool and must never be commanded by it.
Every command here is TRANSCRIBED from the manufacturer manual, not APPROVED.
For the discovery tool, only the allowlists in 01_DISCOVERY_TOOL_SPEC.txt may be sent.

Command Register

Project: Vehicle Harness Functional Tester Document status: Draft — NOT reviewed, NOT approved for hardware execution Created by: P0 documentation extraction from manufacturer manuals held in this repository Governing rule: m365_copilot_agent_setup_for_harness_tester (1).md §3 — "Never invent, autocomplete, infer, or translate an SCPI, VISA, serial, socket, relay-switching, or power-output command. Accept a hardware command only when the user provides an exact excerpt from the programming manual for the exact model/firmware and the reviewed command register identifies the document, revision, page/section, syntax, response, units, prerequisites, and reviewer."

0. How to read this register

Every row carries a Review status. Only APPROVED entries may ever be transmitted to real hardware, and only after Real mode is enabled by the responsible engineer.

Firmware caveat. Every TRANSCRIBED entry below is transcribed from a manual whose own example *IDN? response is 2831E Multimeter,Ver1.0.09.12.03. If the installed unit reports a different firmware version, every entry reverts to unverified until re-checked against the matching manual revision.

Current count: 0 APPROVED. 1 of 4 instruments fully BLOCKED (ITECH). 1 provisional (Tektronix).

1. Instrument transport summary

2. B&K Precision 2831E — TRANSCRIBED

Source document: bk_precision_2831e_manual.pdf (SRC-02), Chapters 5–6. Model scope: 2831E. The same manual also documents model 5491B — 5491B ranges and accuracies differ and must not be used for the 2831E. Reviewer: (none — unreviewed) Bench verification: (none)

2.1 Transport parameters

Port mapping (closes the OBS-007 action). Enumerate by VID_10C4 + PID_EA60 + serial number, never by COM-port order — pyserial's comports() exposes vid, pid and serial_number. Caveat R-DMM-02: CP210x devices are often shipped with identical factory serial strings. Test with both meters connected before relying on serial-based identification; if the serials collide, fall back to a documented physical-port binding and make it a commissioning checklist item.

2.2 Command syntax rules (p.42–45)

• Case-insensitive: FUNC:VOLT:DC = func:volt:dc.
• Short form: drop the 4th letter and everything after it if the 4th letter is a vowel (:immediate → :imm); keep it if a consonant (:format → :form); exception :TCouple → :tc.
• Brackets [ ] mark optional keywords — do not transmit the brackets.
• Angle brackets < > mark parameter types — do not transmit the brackets.
• A space separates command and parameter. No space before or after a colon.
• ; separates commands at the same level; ;: restarts from the root.
• Parameter types: <b> boolean (0/OFF/1/ON), <n> numeric or DEFault/MINimum/MAXimum, <NRf> number, <name> enumerated.

2.3 Common commands (p.62–63)

The 2831E supports only these three common commands (p.45 §6.3). *OPC?, *CLS, *ESR?, *STB?, *WAI are not documented — treat as NOT IMPLEMENTED.

2.4 FUNCtion subsystem (p.47)

<name> ∈ VOLTage:AC, VOLTage:DC, CURRent:AC, CURRent:DC, RESistance, FREQuency, PERiod, DIODe, CONTinuity.

Each function retains its own range / speed / filter / rel setup (p.47). Do not assume a range set under one function applies after switching.

2.5 RESistance subsystem (p.56–59) — primary harness continuity path

:ACQuire prerequisites and error conditions (p.59) — enforce all three in the driver: 1. The instrument must already be on the resistance function; sending it in another function causes an error. 2. The last reading must not have been an overflow. 3. A reading must have been triggered; if none has, an error occurs.

Accuracy prerequisite: the 200 Ω, 2 kΩ and 20 kΩ range accuracies are specified only under REL (p.67 footnote 2). A continuity/resistance recipe that skips the null is out of specification.

2.6 VOLTage subsystem (p.48–51)

Range is specified as the expected reading, not the range name: to select the 200 mV range, send 0.02 (p.49).

2.7 CURRent subsystem (p.52–55)

Manual inconsistencies to raise with the reviewer, not to silently "fix": (a) p.53 gives the NPLC parameter range as 0.1 to 10 but MINimum = 0.5 and MAXimum = 2, which contradicts it. (b) p.52 table gives DC reference as −20 to 20 and AC as 0 to 20; p.54 body text gives AC as −20 to 20 and DC as 0 to 20 — the two are swapped. Encode the narrower of the two readings and flag both to the reviewer.

2.8 FREQuency / PERiod subsystem (p.59–61)

(Threshold range printed inconsistently between p.59 and p.60 — flag to reviewer.)

2.9 TRIGger subsystem (p.61–62)

IMMediate = internal/continuous. BUS = triggered via USB/RS-232 by *TRG. MANual = front-panel Trig key.

2.10 FETCh subsystem (p.62)

Staleness hazard — must be handled in the driver. Because :FETCh? returns the same value until a new reading exists, a poll loop can silently return a stale reading and the test would pass on old data. The driver must use the documented deterministic sequence (§2.12) and must never treat a repeated identical value as a fresh measurement.

2.11 DISPlay subsystem (p.46)

Do not use :DISPlay:ENABle OFF in production recipes. Freezing the display and locking the front panel removes the operator's ability to see what the instrument is doing during an energized test. The speed gain is not worth it. If it is ever used, the application must guarantee re-enable on every exit path including exception, abort and timeout.

2.12 Only documented deterministic read sequence

TRIGger:SOURce BUS      # CR-2831E-090
:FUNCtion RESistance    # CR-2831E-010
:RESistance:RANGe:AUTO ON   # or an explicit range, CR-2831E-024 / -022
*TRG                    # CR-2831E-003  — trigger one measurement
:FETCh?                 # CR-2831E-100  — read it back

Each line is transmitted with the configured terminator, respecting the per-character echo handshake and one-query-per-line rule of §2.1.

2.13 BLOCKED items within the 2831E

3. B&K Precision DAQ3120 — TRANSCRIBED

Source document: manuals/DAQ3120_programming_manual.pdf (SRC-07), DAQ3120 Series Programming Manual, version stamp January 7, 2026, 139 pp. SHA-256 (first 16) 563c57bf11cae55a. Retrieved from B&K Precision's media bucket — see P0-DOC-03_internet_research_findings.md §2. Model scope: DAQ3120 Series. Reviewer: (none — unreviewed) Bench verification: (none) Firmware caveat: unverified against the installed unit. *IDN? returns the firmware version — record it and re-check this register against the matching manual revision.

Switching commands are the highest-risk commands in this project. A wrong route can connect a resistance measurement path to an energized circuit, or short two harness pins together. Nothing in §3.6 may be emitted until the fixture schematic, the channel map and the forbidden-combination table exist and have been reviewed (P0-DOC-01 OBS-009, T-04).

3.1 Syntax and data types (SRC-07 ch. 2–3)

• Standard SCPI: long/short forms, case-insensitive, responses return short form uppercase.
• <NRf> accepts <NR1> integer, <NR2> decimal, <NR3> exponent.
• <Boolean>: ON/1, OFF/0.
• <String>: double-quoted; the quotes are part of the syntax.
• Special keywords: MIN, MAX, DEF, AUTO.

Channel list (@<ch_list>) — SRC-07 §3.3, p.18:

Channel numbers are <slot><channel>: slot 1 → 1xx, slot 2 → 2xx, slot 3 → 3xx. Computed "Computer Channels" are 401–420 (DAQ3120 user manual §5.6.1).

3.2 Common commands (SRC-07 ch. 5, pp.22–26)

3.3 Acquisition control (SRC-07 ch. 6, pp.28–30)

CR-DAQ-025 is architecturally important and has a trap. Manual, §6.4: "When disabled, the instrument acts as a switch, allowing external instruments to measure signals routed through the multiplexer modules." — this is how the DAQ routes harness pins to the two external 2831E DMMs. But: "Changing the state of the internal DMM triggers a Factory Reset (*RST)." So it is a connect-time decision only. Never toggle it mid-sequence: it silently discards the scan list and all channel configuration.

Reading memory is 100,000 readings and wraps — "If memory overflows, the oldest readings are overwritten." For long scans use R? to drain periodically, and never assume FETCh? returned everything.

3.4 CONFigure subsystem (SRC-07 ch. 8, pp.39–45)

Example, verbatim from the manual: CONF:RES 10k,(@101)

3.5 MEASure subsystem (SRC-07 ch. 14, pp.62–67)

MEASure:…? configures and immediately returns a value. Same parameter shapes as CONFigure.

3.6 ROUTe subsystem — SWITCHING, HIGHEST RISK (SRC-07 ch. 17, pp.74–77)

Mandatory design rules for the route layer:

1. Default to CR-DAQ-061 (ROUTe:CLOSe:EXCLusive). Plain ROUTe:CLOSe leaves previously closed channels closed, which on a harness fixture means unintended pin-to-pin connections. Emitting ROUTe:CLOSe must require an explicit, reviewed multi-point intent that has been checked against the forbidden-combination table.
2. Synchronize on ROUTe:DONE?, never on a fixed sleep.
3. Open before de-energizing and after every sequence, including abort, timeout, exception and application close.
4. No route may be emitted at all until T-04 (fixture schematic, pin map, route table, forbidden combinations) exists and is reviewed.

3.7 SENSe — resistance (SRC-07 ch. 18.8, pp.89–92)

For milliohm-level harness continuity, prefer FRESistance (4-wire) with OCOMpensated ON. The datasheet warns that 2-wire without a math null adds 2 Ω of error, and module thermal offset is <1–4 µV, which at 1 mA test current is ~1–4 mΩ. Both settings belong in the reviewed recipe, not in driver defaults.

Other SENSe branches follow the same shape: [SENSe:]FUNCtion[:ON], AVERage:*, VOLTage:* (incl. [SENSe:]VOLTage[:DC]:IMPedance:AUTO), CURRent:*, FREQuency|PERiod:*, TEMPerature:*, STRain:*, TOTalize:*, CAPacitance:*, DIODe:ZERO:AUTO, DIGital:DATA…?.

3.8 TRIGger subsystem (SRC-07 ch. 22, pp.139–140)

3.9 CALCulate — limits and scaling (SRC-07 ch. 7, pp.33–37)

CALCulate:LIMit does not replace application-side pass/fail. Unlike the 2831E, the DAQ can evaluate limits — but the run record must still store the raw reading and the application must still compute the verdict. Instrument limit state may be used for alarm outputs and early abort, never as the sole recorded verdict.

3.10 SYSTem subsystem — identity, errors, LAN (SRC-07 ch. 21, pp.121–137)

CR-DAQ-100 and CR-DAQ-101 change what the application can guarantee. SYSTem:CTYPe? lets the app verify the installed module in each slot at connect time and refuse to run if the configuration does not match the reviewed channel map. SYSTem:ERRor? gives real error reporting — drain the queue after every command batch. Neither has an equivalent on the 2831E.

CR-DAQ-111 SYSTem:PERSona changes the identity string the instrument reports. It must never be used: it would defeat the identity check the project depends on.

Security: Telnet (CR-DAQ-114) and the web interface (CR-DAQ-115) should be disabled on a production station unless IT approves otherwise, and the decision recorded (P0-DOC-01 OBS-006).

3.11 Other subsystems available

DATA:LAST?, DATA:POINts?, DATA:POINts:EVENt:THReshold, DATA:REMove? (ch. 9) · DIGital:INTerface:MODE\|DATA:OUTPut\|DATA:SETup (ch. 10) · DISPlay, DISPlay:TEXT, DISPlay:TEXT:CLEar (ch. 11) · FORMat:READing:ALARm\|CHANnel\|DATE\|TIME\|TIME:TYPE\|UNIT (ch. 12) · HCOPy:SDUMp:DATA?\|FORMat screen dump (ch. 13) · MMEMory:FORMat:READing:*, MMEMory:LOG[:ENABle] (ch. 15) · OUTPut:ALARm:CLEar\|MODE\|SLOPe (ch. 16) · SOURce:CURRent\|VOLTage\|MODE\|MODE:LOCK\|DIGital:DATA[:BYTE]\|:WORD (ch. 19, DM307) · STATus:ALARm\|OPERation\|QUEStionable :CONDition?\|:ENABle\|[:EVENt]?, STATus:PRESet (ch. 20).

FORMat:READing:CHANnel ON is strongly recommended. It prefixes each value with its channel number, so a returned block cannot be silently mis-associated with the wrong harness pin. Likewise FORMat:READing:DATE/TIME for traceable run records.

3.12 Deterministic scan sequence (composed from the above)

*RST                                  # CR-DAQ-002  clears scan list and config
SYST:ERR?                             # CR-DAQ-101  drain the error queue
*IDN?                                 # CR-DAQ-001  record serial + firmware
SYST:CTYP? 1                          # CR-DAQ-100  verify module in each slot
SYST:LFR?                             # CR-DAQ-104  read line frequency, do not assume
FORM:READ:CHAN ON                     # CR-DAQ-...  channel number with every reading
CONF:FRES 100,(@101:110)              # CR-DAQ-031  4-wire, reviewed range
FRES:OCOM ON,(@101:110)               # CR-DAQ-073  cancel thermal EMF
FRES:NPLC 10,(@101:110)               # CR-DAQ-070  reviewed integration time
ROUT:SCAN (@101:110)                  # CR-DAQ-064  reviewed scan list
TRIG:SOUR BUS                         # CR-DAQ-080
TRIG:COUN 1                           # CR-DAQ-081
INIT                                  # CR-DAQ-021
*TRG                                  # CR-DAQ-007
FETC?                                 # CR-DAQ-022
SYST:ERR?                             # CR-DAQ-101  confirm no error was raised

This sequence is TRANSCRIBED, not APPROVED. The channel list is illustrative — real channels require the fixture map (T-04) and the module list (T-08).

3.13 DAQ3120 items still requiring the user manual or bench work