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1 #!/usr/bin/env python
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2
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3 # Copyright (c) 2012
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4 # Daniel O'Connor <darius@dons.net.au>. All rights reserved.
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5 #
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6 # Redistribution and use in source and binary forms, with or without
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7 # modification, are permitted provided that the following conditions
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8 # are met:
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9 # 1. Redistributions of source code must retain the above copyright
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10 # notice, this list of conditions and the following disclaimer.
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11 # 2. Redistributions in binary form must reproduce the above copyright
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12 # notice, this list of conditions and the following disclaimer in the
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13 # documentation and/or other materials provided with the distribution.
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14 #
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15 # THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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16 # ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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17 # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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18 # ARE DISCLAIMED. IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
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19 # FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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20 # DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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21 # OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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22 # HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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23 # LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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24 # OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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25 # SUCH DAMAGE.
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26 #
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27
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28 import math
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29 import rsib
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30 import scpi
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31 import sys
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32
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33 def setup(r):
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34 # Reset to defaults
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35 r.write("*RST")
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36
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37 # Set to single sweep mode
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38 r.write("INIT:CONT OFF")
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39
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40 # Enable display updates
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41 r.write("SYST:DISP:UPD ON")
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42
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43 # Set frequency range
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44 r.write("FREQ:CEN 10.7MHz;SPAN 1MHz")
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45
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46 # Switch marker 1 on in screen A
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47 r.write("CALC:MARK1 ON")
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48
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49 # Enable noise measurement
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50 r.write("CALC:MARK1:FUNC:NOIS ON")
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51
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52 # Set number of sweeps
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53 r.write("SWE:COUN 20")
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54
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55 # Set resolution bandwidth
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56 r.write("SENS1:BAND:RES 10kHz")
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57
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58 # Set video bandwidth (10x res BW)
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59 r.write("SENS1:BAND:VID 100kHz")
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60
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61 def getnoise(r):
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62 # Trigger the sweep
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63 r.write("INIT;*WAI")
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64
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65 # Wait for it to be done
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66 r.write("*OPC?")
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67 opc = scpi.getdata(r.read(60), int)
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68 #print "OPC - %d" % (opc)
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69 assert(opc == 1)
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70
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71 # Set data format
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72 r.write("FORM:DATA ASC")
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73
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74 # Read noise value
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75 r.write("CALC:MARK1:FUNC:NOIS:RES?")
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76 data = r.read(10)
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77 #print "Data - " + data
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78
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79 return float(data)
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80
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81 def setnoise(r, en):
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82 if en:
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83 val = "ON"
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84 else:
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85 val = "OFF"
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86 r.write("DIAG:SERV:NSO " + val)
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87
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88 def calcnf(enrdb, offdb, ondb):
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89 # Not possible but weak results may give it
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90 if ondb <= offdb:
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91 return 0
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92 ydb = ondb - offdb
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93 y = 10 ** (ydb / 10)
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94 enr = 10 ** (enrdb / 10)
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95 nf = 10 * math.log10(enr / (y - 1))
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96 return nf
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97
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98 def donoisetest(r, enr):
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99 print "Acquiring with noise off.."
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100 setnoise(r, False)
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101 off = getnoise(r)
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102 print "Acquiring with noise on.."
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103 setnoise(r, True)
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104 on = getnoise(r)
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105 return off, on, calcnf(enr, off, on)
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106
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107 if __name__ == '__main__':
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108 enr = 15.55 # From back of noise source
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109 r = rsib.RSIBDevice('analyzer')
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110
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111 # ID instrument
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112 r.write('*IDN?')
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113 print "ID is " + r.read(5)
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114
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115 #setup(r)
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116 r.write("INIT:CONT OFF")
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117
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118 while True:
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119 off, on, nf = donoisetest(r, enr)
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120 print "Off %.3f dB, on %.3f dB, NF %.2f" % (off, on, nf)
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121 print "Press enter to perform a new measurement"
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122 sys.stdin.readline()
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123
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