"""Agilent/HP/Keysight 34401A DMM driver (SCPI over GPIB or RS-232)."""
from __future__ import annotations
import time
from instro.dmm import DMMDriverBase
from instro.dmm.types import MeasurementFunction
from instro.lib.transports.visa import VisaConfig, VisaDriver
[docs]
class Agilent34401A(DMMDriverBase):
"""Agilent/HP/Keysight 34401A DMM."""
def __init__(self, visa_resource: str | VisaConfig) -> None:
self._visa = VisaDriver(visa_resource)
self._range: float | None = None
self._resolution: float | None = None
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def open(self) -> None:
"""Open transport, ``*CLS``, then ``SYST:REM`` to disable the front panel and RS-232 echo."""
self._visa.open()
self._visa.write("*CLS")
time.sleep(0.5)
self._visa.write("SYST:REM")
time.sleep(0.5)
self._check_errors()
[docs]
def close(self) -> None:
self._visa.close()
[docs]
def set_measurement_function(self, function: MeasurementFunction) -> None:
"""Configure the function for subsequent reads via a dummy measurement."""
match function:
case MeasurementFunction.DC_VOLTAGE:
self.measure_dc_voltage()
case MeasurementFunction.AC_VOLTAGE:
self.measure_ac_voltage()
case MeasurementFunction.DC_CURRENT:
self.measure_dc_current()
case MeasurementFunction.AC_CURRENT:
self.measure_ac_current()
case MeasurementFunction.TWO_WIRE_RESISTANCE:
self.measure_resistance()
case MeasurementFunction.FOUR_WIRE_RESISTANCE:
self.measure_four_wire_resistance()
case _:
raise NotImplementedError(f"Agilent 34401A does not support {function.name}.")
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def set_digits(self, n: int) -> None:
"""Set the digits (4, 5, or 6) used as the resolution argument in ``MEAS:...?`` commands."""
if n not in (4, 5, 6):
raise ValueError("Agilent 34401A supports 4, 5, or 6 digit resolution.")
res_map = {4: 0.001, 5: 0.0001, 6: 0.00001}
self._resolution = res_map[n]
def _store_range(self, value: float | None) -> None:
"""Cache the range for ``MEAS:...?`` calls. The 34401A's cache is shared across functions, so every ``set_*_range`` delegates here."""
self._range = value
set_dc_voltage_range = _store_range
set_ac_voltage_range = _store_range
set_dc_current_range = _store_range
set_ac_current_range = _store_range
set_two_wire_resistance_range = _store_range
set_four_wire_resistance_range = _store_range
def _build_meas_cmd(self, base_cmd: str) -> str:
"""Build ``MEAS:...?`` appending range when set, and resolution when set alongside it."""
if self._range is None:
return f"{base_cmd}?"
if self._resolution is None:
return f"{base_cmd}? {self._range:.6e}"
return f"{base_cmd}? {self._range:.6e},{self._resolution:.6e}"
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def measure_dc_voltage(self) -> float:
return self._query_checked_float(self._build_meas_cmd("MEAS:VOLT:DC"))
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def measure_dc_current(self) -> float:
return self._query_checked_float(self._build_meas_cmd("MEAS:CURR:DC"))
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def measure_resistance(self) -> float:
return self._query_checked_float(self._build_meas_cmd("MEAS:RES"))
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def measure_four_wire_resistance(self) -> float:
return self._query_checked_float(self._build_meas_cmd("MEAS:FRES"))
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def measure_ac_voltage(self) -> float:
return self._query_checked_float(self._build_meas_cmd("MEAS:VOLT:AC"))
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def measure_ac_current(self) -> float:
return self._query_checked_float(self._build_meas_cmd("MEAS:CURR:AC"))
def _query_checked_float(self, command: str) -> float:
with self._visa.lock():
value = self._visa.query(command)
self._check_errors()
return float(value)
def _check_errors(self) -> None:
err = self._visa.query("SYST:ERR?")
parts = err.strip().split(",", 1)
code_str = parts[0] if parts else ""
code_val = int(code_str) if code_str.lstrip("-+").isdigit() else -1
if code_val != 0:
raise RuntimeError(f"Agilent 34401A reported error: {err.strip()}")
instro