i try to create c# application to read data from weighing scale (HLWagen IT1000). When using RS232 port , the application was able to detect and display the weighing data. Here is my code.

      private void Weighing_Load(object sender, EventArgs e)
    {

           string[] availablePorts = SerialPort.GetPortNames();
        if (!availablePorts.Contains(comPort))
        {
            MessageBox.Show("Make sure the printer is connected to COM1.", "Serial 
             Port Not Found", MessageBoxButtons.OK, MessageBoxIcon.Warning);
            Application.Exit(); 
            return;

           
        }

        // Close and dispose of any existing serial port
        if (_serialPort != null && _serialPort.IsOpen)
        {
            _serialPort.Close();
        }
        if (_serialPort != null)
        {
            _serialPort.Dispose();
        }

        // Create and configure a new SerialPort object
        _serialPort = new SerialPort(comPort, BaudRate, Parity.None, 8,StopBits.One);
        _serialPort.DataReceived += SerialPortOnDataReceived;

        try
        {
            _serialPort.Open(); // Open the serial port
            
        }
        catch (Exception ex)
        {
            MessageBox.Show("Error opening the serial port: " + ex.Message, "Serial 
          Port Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            

        }

    }
        private void SerialPortOnDataReceived(object sender, 
         SerialDataReceivedEventArgs serialDataReceivedEventArgs)
    {
        if (InvokeRequired)     //<-- Makes sure the function is invoked to work 
            properly in the UI-Thread
            BeginInvoke(new Closure(() => { SerialPortOnDataReceived(sender, 
          serialDataReceivedEventArgs); }));     //<-- Function invokes itself
        else
        {
            int dataLength = _serialPort.BytesToRead;
            byte[] data = new byte[dataLength];
            int nbrDataRead = _serialPort.Read(data, 0, dataLength);
            if (nbrDataRead == 0)
                return;
            string str = System.Text.Encoding.UTF8.GetString(data);


            





         

            // Extract the weight measurement and "S S" tag from the incoming data
            int startIndex = str.IndexOf("S S")+1;
            if (startIndex < 0 || startIndex >= str.Length)
            {
                // Handle the error here, such as by logging the error or displaying 
              a message to the user
                return;
            }

            int endIndex = str.IndexOf("k", startIndex);
            if (endIndex < 0 || endIndex > str.Length)
            {
                // Handle the error here, such as by logging the error or displaying 
             a message to the user
                return;
            }

            string weightStr = str.Substring(startIndex, endIndex - startIndex);

            //test display
            //MessageBox.Show(weightStr);

            // Trim the "k" character from the weight measurement
            weightStr = weightStr.TrimEnd('k');

            // Display the weight measurement and "S S" tag in the label
            weight_label.Text = $"{weightStr} kg";
            weightStr = str.Substring(startIndex, endIndex - startIndex - 1);
            current_weight =weightStr;
            current_weight = float.Parse(weightStr);

               using (StreamWriter writer = new StreamWriter("log_weight.txt", true))
            {
                writer.WriteLine(weightStr);
                writer.Flush();
            }


        }
    }

and here the result:

S D      2.535 kg
S D      2.535 kg
S S      2.534 kg
S S      2.534 kg
S S      2.534 kg
S S      2.534 kg
S S      2.534 kg
S S      2.534 kg
S S      2.534 kg
S S      2.534 kg
S S      2.534 kg
S S      2.534 kg
S S      2.534 kg
S S      2.534 kg
S S      2.534 kg
S S      2.534 kg
S S      2.534 kg
S S      2.534 kg
S S      2.534 kg
S D      2.575 kg
S D      2.555 kg

but When i used converter RS-232 USB to Serial converter, using same code the data is not consistence:

S S 2.570 kg
S D 2.565 kg
S D 2.535 kg

S D
2.
535 kg

S D
2.540
kg

S
D
2.550 kg

S
D
2.5
50 kg

S
D 2.
595 kg

S
D 2.
610 kg

S
D 2.
620 kg

S
D
2.625 kg

S
D 2.6
30 kg

S
D
2.630 k
g

S
D 2.6
25 kg

S
D 2.
620 kg

S
D 2.
600 kg

S
D 2
.615 kg

S
D
2.575 k
g

S
D 2
.565 kg

S D
2.555
kg

S
D
2.545
kg

S
D 2
.535 kg

S D
2.535
kg

S
D 2.
535 kg

S
D 2.
535 kg

S D
2.54
5 kg

S
D 2.
560 kg

S
D
2.555 k
g

S
D 2.
555 kg

S
D
2.550 kg

S D
2.550
kg

S
D 2.5
50 kg

S
D 2.5
45 kg

S
D 2.4
75 kg

S
D
2.45
5 kg

S
D 2
.490 kg

S D
2.4
50 kg

S
D
2.355 kg

S
D 1.
615 kg

S
D 1.
425 kg

S
D 1.
405 kg

S
D 1
.410 kg

i need help how to handle the data like this , thank you!