知识库文章介绍了使用 Python 编程语言对 Magna-Power 可编程电源产品进行编程。Python 是一种流行的编程语言，以其简单性、代码可读性而闻名，并且不需要任何特殊编译。Python 的易用性和快速的学习曲线使其成为创建程序以控制、进行测量甚至为可编程仪器创建绘图的绝佳语言。此外，Magna-Power 对可编程仪器标准命令 （SCPI） 的广泛支持意味着该公司的产品可以通过简单、直观的命令在 Python 中轻松控制。

Magna-Power 的产品支持多种不同的通信接口，包括：RS-232、TCP/IP 以太网、USB、RS-485 和 IEEE-488 GPIB。尽管接口不同，但特定产品系列的 SCPI 命令是相同的。SCPI 命令记录在相应产品系列的用户手册中。创建 Python 程序时，接口之间的唯一区别是设备连接的设置。

USB、串行或 RS-485，它们将使用 pySerial 创建与仪器的串行连接：

import serial
conn = serial.Serial(port='COM4', baudrate=115200)

xGen 产品的串行波特率为 115200，而非 xGen 产品的串行波特率为 19200。端口位置由您的作系统定义。在 Windows 中，可以在设备管理器中找到此端口。

后续通过串行连接发送和接收命令将如下所示：

conn.write('*IDN?\n'.encode())
print(conn.readline())

TCP/IP 以太网连接设置如下：

import socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(('192.168.0.86', 50505))

后续通过 TCP/IP 以太网连接发送和接收命令将如下所示：

s.sendall('*IDN?\n'.encode())
print(s.recv(4096))

IEEE-488 GPIB连接将需要PyVISA，连接如下：

import visa
rm = visa.ResourceManager()
inst = rm.open_resource('GPIB0::12::INSTR')

随后通过 IEEE-488 GPIB 连接发送和接收命令将如下所示：

print(inst.query("*IDN?"))

以下示例提供了使用 xGen MagnaDC 电源的更深入的示例 Python 程序。使用 Python 对非 xGen MagnaDC 可编程直流电源进行编程几乎相同，只是对 SCPI 命令进行了细微的更改，如相应产品系列的用户手册中所述。

以下基本示例创建 TCP/IP 以太网连接，发送一些初始化命令，启用 DC 输出，将当前级别提高到 5 Adc，等待 20 秒，然后关闭。

# Import time: Time access and conversions to allow for pausing
# Import socket: Low-level networking interface to allow for socket programming
import time, socket
# Create socket object s with (host, port)
# Define host as hostname in Internet domain
# Define socket type as stream, allowing a port number to be defined
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
# Connect to product's IP address address at default 50505 socket
s.connect(('192.168.0.86', 50505))
# Send SCPI command requesting the product to identify itself
s.sendall('*IDN?\n'.encode())
# Receive the product's response and display it in the terminal
print(s.recv(4096))
# Send SCPI command to configure the MagnaDC for local control
s.sendall('CONF:SOUR 0\n'.encode())
# Send SCPI command to set the DC output current to 0 Adc before enabling DC input
s.sendall('CURR 0\n'.encode())
# Send SCPI command to enable the MagnaDC power supply output
s.sendall('OUTP:START\n'.encode())
# Send SCPI command to set the DC input current to 5 Adc
s.sendall('CURR 5\n'.encode())
# Wait 20 seconds
time.sleep(20)
# Send SCPI command to disable the DC output
s.sendall('OUTP:STOP\n'.encode())
# Close the communication channel to the product
s.close()

以下示例创建与产品的串行连接，确定它是什么产品，然后发送一系列电流命令，每个电流电平之间间隔 20 秒。这种类型的程序也可以扩展为循环显示电压、功率和电阻值。

# Import pySerial, which encapsulates the serial port access
# Import time: Time access and conversions to allow for pausing
import serial, time
# Create serial connection object with default baudrate for MagnaLOADs
conn = serial.Serial(port='COM4', baudrate=115200)
# Send SCPI command requesting the product to identify itself
conn.write('*IDN?\n'.encode())
# Receive the product's response and display it in the terminal
print conn.readline()
# Create array of current set points
currSetPoints = [50, 100, 150, 250]
# Send SCPI command to configure the MagnaDC power supply for local control
s.sendall('CONF:SOUR 0\n'.encode())
# Send SCPI command to enable the MagnaDC power supply
conn.write('OUTP:START\n'.encode())
# For each entry in currSetPoints array
# Print static text and current set point to the terminal
# Send the new set point to the MagnaDC power supply
# Wait 20 seconds
for currSetpoint in currSetPoints:
    print 'Setting Current to %s A' % currSetpoint
    conn.write('CURR {0}\n'.format(currSetpoint).encode())
    time.sleep(20)
# Send SCPI command to disable the MagnaDC power supply output
conn.write('OUTP:STOP\n'.encode())
# Close the communication channel to the product
conn.close()

在最后一个深入的示例中，xGen MagnaDC 电源被编程为使用从逗号分隔值 （.csv） 文件读取的设定点和时间对电池进行放电，使用产品的高精度测量命令测量直流输入，然后提供测量数据与时间的关系图。该程序可以进一步扩展以生成 PDF 测试报告，集成测量数据、绘图以及来自其他仪器的信息。

# Import plotting library Matplotlib
# Import .csv parser
# Import pySerial, which encapsulates the access for the serial port
# Import time: Time access and conversions to allow for pausing
# Import numpy for mathemetical manipulation of arrays
import matplotlib.pyplot as plt
import csv, serial, time
import numpy as np

# Create serial connection object with default baudrate for xGen products
conn = serial.Serial(port='COM8', baudrate=115200)
# Create an empty numpy data array 999 rows, 4 columns
outputSamples = np.empty([999, 3])
iSample = 0

# Send SCPI command to configure the MagnaDC for local control
s.sendall('CONF:SOUR 0\n'.encode())
# Send SCPI command to enable the MagnaDC power supply output
conn.write('OUTP:START\n'.encode())

# Open data stream to .csv file. .csv has two columns:
# Column 1: Current set point in amperes
# Column 2: Time in seconds
# The first row is headers
with open('example_profile.csv', 'r') as csvfile:
	# Read the .csv file using comma (,) as the delimeter
    dataset = csv.reader(csvfile, delimiter=',')
	# Skip the header row
    next(dataset)
	# Split the dataset up to rows
    rows = list(dataset)
	# Create an empty array for measurements, the same length as .csv row numbers
    inputSamples = np.empty([len(rows), 2], dtype=float)
	# Record the time that the measurements began
    testStartTime = time.time()
	# Run for loop while there are still rows of data left
    for idx, data in enumerate(rows):
		# Store row data to array
        inputSamples[idx] = [data[0], data[1]]
		# Send SCPI command to MagnaDC power supply to current set point at present row
        conn.write('CURR {0}\n'.format(data[0]).encode())
		# Determine how long the MagnaDC power supply should stay at this current set point
        stopTime = testStartTime + int(data[1])
		# Run while loop while there is still time left
        while time.time() < stopTime:
			# Send SCPI command to MagnaDC Power supply to measure all DC output variables
            conn.write('MEAS:ALL?\n')
			# Get the MagnaDC power supply's response and split it up into its respective variables
            [curr, volt, pwr] = (conn.readline()).split(',')
			# Round measurements and store them to array, along with with time
            outputSamples[iSample] = ([round(float(curr), 2), round(float(volt), 2), round(time.time() - testStartTime, 2)])
            iSample += 1
            time.sleep(0.5)

# Send SCPI command to disable Magna DC power supply output 
conn.write('OUTP:STOP\n'.encode())

# Create a plot series of current vs. time
plt.subplot(2, 1, 1)
plt.plot(outputSamples[0:iSample, 2], outputSamples[0:iSample, 0], 'r--')
plt.ylabel('Output Current(A)')
plt.title('I-V Profile')

# Create a plot series of voltage vs. time
plt.subplot(2, 1, 2)
plt.plot(outputSamples[0:iSample, 2], outputSamples[0:iSample, 1], 'b--')
plt.xlabel('Time (s)')
plt.ylabel('Output Voltage(V)')

# Show the plot
plt.show()