c#读串口数据问题（rs232）
C#通過com口讀測量仪器数据，测量时用超级终端能读到数据（C#com口参数设置与超级终端都是一样的）

1、用超級終端可以正常讀取數據，附圖

2、用C#調試時只有開關設備才能讀到數據，测量仪测试时收不到数据，是怎么回事？


问题：C#com口参数设置与超级终端都是一样的，C#为什么只有在开关设备时读到数据，测试仪测试时读不到数据是怎么回事？

详见代码
 private void Form1_Load(object sender, EventArgs e)
  {
   
   
  this.cmbBPS.Text = "9600";
  this.cmbCheck.Text = this.cmbCheck.Items[0].ToString();
  this.cmbDataLen.Text = "8";
  this.cmbStopBit.Text = "1";
  this.cmbSerialPortNo.Text ="COM1";
   
  try
  {
  if (this.serialPort1.IsOpen == false)
  {
  this.serialPort1.Open();
  this.btnOpenSerialPort.ImageIndex = 0;
  this.btnOpenSerialPort.Text = "关闭串口";
  }
  }
  catch
  {
  MessageBox.Show(this, "打开串口失败！串口不存在或其它设置占用", "打开串口失败", MessageBoxButtons.OK, MessageBoxIcon.Error);
  }  
  }

   
  /// <summary>
  /// 使用异步回调机制来显示数据到主界面
  /// </summary>
  /// <param name="text"></param>
  private void SetText(string text)
  {
  string str = "";
  if (this.txtReceive.InvokeRequired)
  {
  SetTextCallback d = new SetTextCallback(SetText);
  this.Invoke(d, new object[] { text });
  }
  else
  {
  int i = text.IndexOf("@");
  str = text.Substring(0, i);
  this.lbRcvBytes.Text = "R:" + str;
  //接收到的数据
  this.txtReceive.Text += text.Substring(i + 1, text.Length - i - 1); ;
  this.txtReceive.SelectionStart = this.txtReceive.Text.Length;
  this.txtReceive.ScrollToCaret();
  //接收的数据长度

  }
  }

   

  private void serialPort1_DataReceived(object sender, SerialDataReceivedEventArgs e)
  {
   
  byte[] receviedBuf;
  SerialPort sp = (SerialPort)sender;
  string str = "";
  int rcvByteLen=0;
  try
  {
  receviedBuf = new byte[sp.BytesToRead];

  int itemp = sp.BytesToRead;
  for (int i = 0; i < itemp; i++)
  {
  receviedBuf[i] = Convert.ToByte(sp.ReadByte());
  rcvByteLen++;
  }


  foreach (byte rcvByte in receviedBuf)
  {
  if (this.chRcvHex.Checked == false)
  {

  if (rcvByte < 128)
  {
  str += Microsoft.VisualBasic.Strings.Chr(rcvByte).ToString();
  this.lastRcvByte = 0;
  }
  else