22-EFT.WP.Metrology.Instrument v1.0 | Chapter 13 — Data Interfaces & Metadata (SCPI / IVI / manifest)

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Chapter 13 — Data Interfaces & Metadata (SCPI / IVI / manifest)

One-Sentence Objective
Centering on standardized SCPI/IVI interfaces and manifest.instrument.*, unify acquisition, control, and traceability metadata so that dimensions, timebase, and compliance are published consistently.

I. Scope and Objects

1. Scope
   • Applies to general-purpose measurement instruments accessed via SCPI (VISA/TCPIP/USB/GPIB/Serial) and IVI (IVI-C/IVI-COM) drivers.
   • Covers the control plane (configuration/status/errors) and the data plane (waveforms/scalars/event streams), for both batch and streaming acquisition.
   • Outputs standardized datasets and manifests: manifest.instrument.*, plus signatures and traceability fields.
2. Objects
   • Session sess, resource identifier resource, command set cmds, data block blob.
   • Time & timebase: ts, tau_mono, t_hw, offset/skew/J.
   • Metrology & uncertainty: y, unit(y), dim(y), u(y), U = k * u_c.
   • Traceability: *IDN?, firmware_ver, driver_ver, cal_cert_id, hash_sha256(blob), TraceID, signature.
3. Outputs
   Unified-field dataset ds, aligned ts, a unit-normalization report, snapshots of error & status registers, manifest.instrument.*, and an acceptance report.

II. Terms and Variables

• Interfaces & drivers: SCPI, IVI, VISA, OPC?, SYST:ERR?, *CLS, *RST.
• Configuration & status: MEAS:FUNC, SENS:FUNC, SENS:AVER, TRIG:SEQ, ACQ:SRATE, BAND, RANGE.
• Metadata keys: vendor, model, serial, firmware_ver, driver_ver, cal_date, RefCond.
• Errors & events: STB, SRQ, queue_len, err_code, err_msg.
• Manifest & signatures: manifest.instrument.meta, manifest.instrument.session, hash_sha256(blob), signature.

III. Postulates P713-*

• P713-1 (Idempotent & discoverable interface): each session must identify via *IDN?, then clear queues with *CLS before entering controlled state.
• P713-2 (Unified timebase): align data-time semantics on tau_mono; publish on ts, recording offset/skew/J.
• P713-3 (Dimensional conservation): before computation, run repair_units and enforce check_dim( y - f(x) ).
• P713-4 (Explicit errors): after every acquisition, query SYST:ERR? and status registers and persist results.
• P713-5 (Traceability closure): record *IDN?, firmware_ver, driver_ver, cal_cert_id, RefCond, and compute hash_sha256(blob) for every blob.
• P713-6 (Manifest as source of truth): publication relies solely on manifest.instrument.* as the trusted source, with verifiable signatures.

IV. Minimal Equations S713-*

• S713-1 (Time mapping)
  ts = t_ref + offset + skew * ( t_hw - t0 ) + eps_J, where t_hw is the hardware timestamp and eps_J is the jitter residual.
• S713-2 (Time uncertainty propagation)
  u(ts)^2 = u(offset)^2 + ( t_hw - t0 )^2 * u(skew)^2 + u(J)^2.
• S713-3 (Dimensional check)
  check_dim( y_norm - y_spec ) = true, where y_norm is the unit-normalized quantity and y_spec is the specification-domain quantity.
• S713-4 (Data-plane stability)
  rho = lambda / mu < 1, where lambda is the enqueue (acquisition) rate and mu is the decode/persist service rate, ensuring streaming stability.
• S713-5 (Signature & integrity)
  sig_ok = ( signature == Sign( hash_sha256(blob), pk ) ).

V. Metrology Procedure M70-13 (Connect → Configure → Acquire → Verify → Persist)

1. Session ingress & handshake
   • Open resource, send *CLS to clear errors/status; query *IDN? to capture the device fingerprint; pull firmware_ver, driver_ver.
   • Read cal_cert_id, cal_date, and RefCond; verify validity and environmental consistency.
2. Mode & parameter configuration
   • Per plan, issue MEAS:FUNC, SENS:FUNC, RANGE, BAND, ACQ:SRATE, TRIG:SEQ, etc.
   • Confirm completion with *OPC?; record the final, effective configuration via read-backs (avoiding shadow state).
3. Acquisition & timestamping
   • Read the blob and t_hw. If no hardware timestamp is provided, mark the driver capture instant and record J.
   • Call align_timebase: map to tau_mono and publish ts, carrying offset/skew/J and u(ts).
4. Decoding & metrological harmonization
   • decode_scpi_blob(blob) → ds_raw; run repair_units to finish unit normalization and check_dim.
   • Compute U = k * u_c where required and fold into field-level uncertainties.
5. Error & status verification
   Query SYST:ERR? and read STB/SRQ; persist err_code/err_msg/queue_len. If any error is present, mark q_score for down-weighting.
6. Persistence & manifest
   Hash both blob and structured outputs with hash_sha256; generate and sign manifest.instrument.*; write TraceID and a closed dependency set.

VI. Contracts & Assertions C70-13*

• iface.idn.ok: *IDN? matches vendor/model/serial.
• iface.error.empty: after acquisition, SYST:ERR? = 0,"No error"; queue_len = 0.
• time.align.ok: |offset| ≤ offset_max, |skew| ≤ skew_max, J ≤ J_max, u(ts) ≤ u_ts_max.
• units.dim.ok: all numeric fields satisfy check_dim(expr) and use whitelisted units.
• throughput.ok: rho < rho_max, sample_loss_rate ≤ slr_max.
• calib.valid: cal_cert_id present and unexpired; RefCond persisted.
• manifest.signed: sig_ok = true, unique(TraceID), non_decreasing(ts).

VII. Implementation Bindings I70-13* (Interface Prototypes & Invariants)

• open_session(resource) -> sess (invariant: re-entrant; timeouts & retries enforced)
• scpi_handshake(sess) -> {idn, firmware_ver, driver_ver} (invariant: error queue empty after *CLS)
• configure_instrument(sess, cfg) -> cfg_effective (invariant: *OPC? = 1)
• stream_measure(sess, plan) -> {blob, t_hw, meta} (invariant: device-side packing/marking preserved)
• decode_scpi_blob(blob) -> ds_raw (invariant: compatible with binary/ASCII)
• collect_and_align(ds_raw, sync_ref) -> ds (invariant: writes ts, offset/skew/J, u(ts))
• query_metadata(sess) -> meta (includes cal_cert_id, RefCond, *IDN?, etc.)
• emit_instrument_manifest(meta, ds, policy) -> manifest.instrument (invariant: hash_sha256 and signature present)
• assert_instrument_contract(ds, meta, rules) -> report (invariant: covers all C70-13* assertions)

VIII. Cross-References

• Timebase & arrival time: EFT.WP.Metrology.TimeBase v1.0, Chapters 2, 4, 8–9; synchronization & links: EFT.WP.Metrology.Sync v1.0, Chapters 4–8.
• Cleaning & publication contracts: EFT.WP.Methods.Cleaning v1.0, Chapter 10 and Appendix C.
• Multi-instrument harmonization: Chapter 12 of this volume; uncertainty publication: Chapter 10 and CrossStats v1.0 Appendix E.
• Imaging chain (cameras/spectrometers): Methods.Imaging v1.0, Chapters 3–4.

IX. Quality Metrics & Risk Control

• SLI
  session_open_latency_ms, cmd_roundtrip_ms_p95, scpi_error_rate, sample_loss_rate, ts_skew_p95, u(ts)_p95, manifest_emit_latency_ms.
• SLO (examples)
  scpi_error_rate ≤ 0.1%, sample_loss_rate ≤ 0.01%, ts_skew_p95 ≤ 1e-6 s, manifest_emit_latency_ms ≤ 500.
• Risk control & rollback
  On iface.error.empty failure, auto-issue *CLS and re-configure; on time.align.ok failure, degrade to local t_hw with explicit J labeling; block publication and alert on manifest signature failures.

Summary
Through P713-* / S713-* / M70-13 / C70-13* / I70-13*, this chapter specifies an end-to-end standard from SCPI/IVI ingress, configuration, and acquisition to timebase alignment, dimensional checks, and signed-manifest publication. All data are served from manifest.instrument.* as the single source of truth, closing the loop with the TimeBase/Sync/Cleaning volumes.