Agilent E3631A Power Supply Accuracy

#!/usr/bin/env arch -i386 python
 
from visa import *
import time, csv
 
# CSV open file
f = open('out.csv', 'w')
writer = csv.writer(f)
 
# Agilent 34401A
dmm_addr = 'ASRL1'
dmm = SerialInstrument(dmm_addr, baud_rate=9600, data_bits=7, stop_bits=2, 
                       parity=even_parity, term_chars=CR+LF, 
                       end_input=term_chars_end_input, send_end=True, delay=1)
 
# Set it up for remote access, reset to factory, remote again
print "Resetting DMM"
dmm.write('SYST:REM')
dmm.write('*RST')
time.sleep(20)
dmm.write('SYST:REM')
print dmm_addr + ": " + dmm.ask('*IDN?')
 
# Agilent E3631A
pwr_addr = 'ASRL4'
pwr = SerialInstrument(pwr_addr, baud_rate=9600, data_bits=7, stop_bits=2, 
                       parity=even_parity, term_chars=CR+LF, 
                       end_input=term_chars_end_input, send_end=True, delay=1)
 
# Set it up for remote access, reset to factory, remote again
print "Resetting Power Supply"
pwr.write('SYST:REM')
pwr.write('*RST')
time.sleep(20)
pwr.write('SYST:REM')
print pwr_addr + ": " + pwr.ask('*IDN?')
 
# Loop from 0 to 6 volts in 10mV increments cyc times
cyc = 15
 
voltages = []
volt = 0
for cnt in range(600):
	voltages.append(volt)
	volt = volt + 0.01
 
writer.writerow(voltages)
 
for I in range(cyc):
	tarr = []
	for J in range(len(voltages)):
		setpoint = voltages[J]
		# Set the power supply to the setpoint
		pwr.write('APPL P6V, ' + str(setpoint) + '; OUTP ON')
		# Let the output settle 1 seconds
		time.sleep(1)
		# Measure the output
		meas = dmm.ask('MEAS:VOLT:DC? 10, MAX')
		tarr.append(meas)
		# Tell the user what's up
		print("Cycle: " + str(I) + 
			  " set:" + str(setpoint) + 
			  "V meas:" + str(meas) + "V")
		# Turn off the output
		pwr.write('OUTP OFF')
	# Write tarr to the file
	writer.writerow(tarr)
 
# Close the file
f.close()

#!/usr/bin/python
 
import csv
from pylab import * 
 
f = open('out.csv', 'r')
reader = csv.reader(f)
cols = zip(*reader) # transpose reader so it's columnwise
 
# Measured data, set voltage, tolarance array (according to the datasheet)
data = []; setv = []; tol = []
 
# Every 100mV
for col in cols[::10]:
	# Build the set voltage array
	setv.append(float(col[0]))
	# Build the tolarance voltage array
	tol.append(float(col[0])*0.001+0.005)
	# Build the linearity array
	data.append(map(lambda x: float(x) - float(col[0]), col[1:]))
 
# Close the CSV file
f.close()
 
# Figure and axis
fig = figure()
ax = fig.add_subplot(111)
ax.boxplot(data)
 
# Titles and labels
ax.set_title("Agilent E3631A P6V Linearity")
ax.set_xlabel("Set Voltage (volts)")
ax.set_ylabel("Deviation from Set Voltage (volts)")
 
# Show every 500mV on the axis
axlab = map(lambda x: x if x % 0.5 == 0 else "" ,setv)
ax.set_xticklabels(axlab, rotation = 45)
ax.fill_between(range(1,len(tol)+1), tol, tol*(-1*ones(len(tol))), 
		facecolor='yellow', alpha='0.25')
 
# Display the figure
show()