"""Nano-volt meter.
"""
from time import sleep
from src.core import instrument as inst
from src.core.action import Action
from src.core.action import ActionSpec, ParameterSpec
from src.core.instrument import visa
[docs]class HP34420A(inst.Instrument):
"""Driver for an HP34420A: Nanovolt meter."""
def __init__ (self, experiment, name='HP34420A: Nanovolt meter', spec=None):
super(HP34420A, self).__init__(experiment, name, spec)
self._instrument = None
self._info = 'Name: ' + self.getName()
self._info += '\nModel: HP34420A Nanovolt meter'
[docs] def initialize (self):
"""Open communication with the nanovolt meter."""
self._instrument = visa.instrument(self.getSpecification()[0].value)
self._info += '\n' + self._instrument.ask('*IDN?')
[docs] def finalize(self):
"""Close the communication channel."""
self._instrument.close()
[docs] def getAddress (self):
"""Return the instrument's VISA resource address."""
return self.getSpecification()[0].value
[docs] def readSingleVoltage(self):
"""Read the voltage."""
return (self._instrument.ask('MEASure?'),)
[docs] def readAverageVoltage(self, numavg, intertime):
"""Read the average voltage."""
total = 0.0
for _ in range(numavg):
total += float(self._instrument.ask('MEASure?'))
sleep(intertime)
return (total/numavg, )
[docs] def getActions (self):
"""Get the list of supported actions."""
return [
ActionSpec('read_average_voltage', Action,
{'experiment': self._expt,
'instrument': self,
'description': 'Read average voltage',
'inputs': [
ParameterSpec('numavg',
{'experiment': self._expt,
'description': 'Number of averages',
'formatString': '%d',
'binName': None,
'binType': None,
'value': 3,
'allowed': None,
'instantiate': False}),
ParameterSpec('intertime',
{'experiment': self._expt,
'description': 'Time between averages (s)',
'formatString': '%.3f',
'binName': None,
'binType': None,
'value': 0.01,
'allowed': None,
'instantiate': False})
],
'outputs': [
ParameterSpec('avgv',
{'experiment': self._expt,
'description': 'Average Voltage',
'formatString': '%.6e',
'binName': 'V_avg',
'binType': 'column',
'value': 0,
'allowed': None,
'instantiate': False})
],
'string': ('Average voltage $numavg times, '
'spaced by $intertime s'),
'method': self.readAverageVoltage
}
),
ActionSpec('read_single_voltage', Action,
{'experiment': self._expt,
'instrument': self,
'description': 'Read single voltage',
'outputs': [
ParameterSpec('voltage',
{'experiment': self._expt,
'description': 'Voltage',
'formatString': '%.6e',
'binName': 'Voltage',
'binType': 'column',
'value': 0.0,
'allowed': None,
'instantiate': False})
],
'string': 'Take a single voltage measurement.',
'method': self.readSingleVoltage
}
)
]
#===========================================================================
# Class methods
#===========================================================================
@classmethod
[docs] def getRequiredParameters(cls):
"""Return the list of required parameters for the HP34420A."""
return [inst.InstrumentParameter('VISA Address', '',
inst.getVisaAddresses, '%s')]