Python interface and utility functions for SR850 lock-in amplifier.

SR850-lockin.py

# Talk to SR850 lockin amplifier
# version 1, 2014-01-20
# Amar

import visa
import numpy as np
from datetime import date
import time

class LIA(visa.SerialInstrument):
    # Lock-in amplifier, SR850

    def __init__(self,portName):
        visa.SerialInstrument.__init__(self,portName)
        self.timeout = 3
        self.id = self.ask("*IDN?")
        
    def characterize(self):
        warnings = ""
        print self.id
        print "Sensitivity = ", self.ask("SENS?")
        print "Reserve = ", self.ask("RSRV?")
        if self.ask("RSRV?")!="0": warnings+= "** Warning! Dynamic reserve is not 0 dB ** \n"
        print "Time constant = ", self.ask("OFLT?")    
        print "Traces = ", self.ask("TRCD?1"), self.ask("TRCD?2"), self.ask("TRCD?3"), self.ask("TRCD?4")

        FMOD = self.ask("FMOD?")
        if FMOD == "0": FMODString = "internal"
        elif FMOD == "1": FMODString = "internal sweep"
        elif FMOD == "2": FMODString = "external"
        print "Ref. source = ", FMODString

        print "Ref. frequency = ", self.ask("FREQ?")    
        print "Ref. phase = ", self.ask("PHAS?")    
        print "Ref. sine level = ", self.ask("SLVL?")
        print 
        print warnings
        print
    def setf(self,fi):
        self.write("FREQ " + `fi`)
    def setphase(self,p):
        self.write("PHAS " +`p`)
            
    def getAverage(self,channel=1,N=400):
        # channel #s: 1 = X, 2 = Y, 3 = R, 4 = Theta
        S = []
        for i in range(N): S.append( float(self.ask("OUTP?" + `channel`)) )
        S_avg = np.average(S)
        S_std = np.std(S)
        return S_avg, S_std


    def scanP(self,f,channel=1,N=100,std=False):
        # channels: 1 = X, 2 = Y, 3 = R, 4 = Theta
        output, err = [], []
        for fi in f:
            self.setf(fi)
            print self.ask("FREQ?"),
            
            x = []
            for i in range(N): x.append( float(self.ask("OUTP?"+`channel`)) )
            x_avg = np.average(x)            
            output.append( x_avg )
            x_std = np.std(x)
            err.append( x_std )
            
        if std: return output, err
        else: return output

    def scanR(self,f,trace=1,N=100,std=False):
        # traces: 1,2,3,4
        output, err = [], []
        for fi in f:
            self.setf(fi)
            print self.ask("FREQ?"),
            
            x = []
            for i in range(N): x.append( float(self.ask("OUTR?"+`trace`)) )
            x_avg = np.average(x)            
            output.append( x_avg )
            x_std = np.std(x)
            err.append( x_std )
            
        if std: return output, err
        else: return output