SerialPort.DataReceived返回奇怪的结果

我目前正在使用一种名为Fluke 5500A多产品校准设备的设备。我用C#编写了一个小程序来与它交互，并了解它的工作原理，但不幸的是，SerialPort.DataReceived给了我一些非常奇怪的结果。这个程序不长，所以我要把它全部发布在这里：

class Program
{
    static public bool isExecuting = true;
    static private string serialCommand;
    static private string dataReceived;
    static void Main(string[] args)
    {
        SerialPortConnection serialPort = new SerialPortConnection();
        serialPort.OpenSerialConnection();
        while (isExecuting == true)
        {
            Console.WriteLine("Enter a command or type q to quit.");
            serialCommand = Console.ReadLine().ToUpper();
            if (serialCommand == "Q")
                isExecuting = false;
            else if (serialCommand == "CLEAR")
                Console.Clear();
            else
            {
                dataReceived = serialPort.WriteSerialConnection(serialCommand);
                Console.WriteLine(dataReceived);
            }
        }
        serialPort.CloseSerialConnection();
    }
}

}

我的SerialPortConnection类：

public class SerialPortConnection
{
    private SerialPort serialPort;
    private string dataReceived = "none";
    public SerialPortConnection(string comPort = "Com3", int baud = 9600, System.IO.Ports.Parity parity = System.IO.Ports.Parity.None, int dataBits = 8, System.IO.Ports.StopBits stopBits = System.IO.Ports.StopBits.One)
    {
        serialPort = new SerialPort(comPort, baud, parity, dataBits, stopBits);
    }
    public void OpenSerialConnection()
    {
        try
        {
            serialPort.Open();
        }
        catch (Exception e)
        {
            Console.Write("'nError");
            Console.Write(e);
        }
    }
    public string WriteSerialConnection(string SerialCommand)
    {
        try
        {
            serialPort.Write(String.Format(SerialCommand + "'r"));
            dataReceived = serialPort.ReadExisting();
            return dataReceived;
        }
        catch (Exception e)
        {
            Console.Write("'nError");
            Console.Write(e);
            return "Execution Unsuccessful";
        }
    }
    public void CloseSerialConnection()
    {
        try 
        {
            serialPort.Close();
        }
        catch (Exception e)
        {
            Console.Write("'nError");
            Console.Write(e);
        }
    }
}

我目前的问题是控制台的输出看起来像这样：

Enter a command or type q to quit.
*IDN?
Enter a command or type q to quit.
OUT 50V <-- Command input
*IDN? <-- Previous command echoed back
FLUKE,5500A,8030005,2.61+1.3+2.0+* <-- Data received from previous command
161>
Enter a command or type q to quit.
OPER
OUT 50V
162>
Enter a command or type q to quit.
STBY
OPER
163>
Enter a command or type q to quit.
*RST
STBY
164>
Enter a command or type q to quit.

命令执行得很好，但控制台的输出似乎是执行的最后一个命令以及该命令返回的任何数据。我不知道为什么会这样。

编辑：

感谢Robert p的回答，我实现了以下代码：

var received = "";
bool isReading = true;
while (isReading == true)
{
    try
    {
        received += serialPort.ReadExisting();
        if (received.Contains('>'))
            isReading = false;
    }
    catch (Exception e)
    {
    }
}
Console.WriteLine(received);

+----+            +----------+           +------------+
|Your|--Command-->|Serial    |---UART--->|    Device  |
|Code|            |Port Obj  |           |            |
+----+            +----------+           +------------+
+----+            +----------+           +------------+
|Your|<--Read-----|Serial    |           |Device      |
|Code| (is empty) |          |           |(processing)|
+----+            +----------+           +------------+
+----+            +----------+           +------------+
|Your|            |Serial    |<-response-|Device      |
|Code|            |(has data)|           |(responding)|
+----+            +----------+           +------------+
+----+            +----------+           +------------+
|Your|--Command2->|Serial    |---UART--->|    Device  |
|Code|            |(has data)|           |            |
+----+            +----------+           +------------+
+----+            +----------+           +------------+
|Your|<--Read-----|Serial    |           |Device      |
|Code| (previous  |          |           |(processing)|
+----+  response) +----------+           +------------+