using System;
using System.Text.RegularExpressions;
 
public class Test
{
public static void Main()
{
 
Regex.Match(
    @"Time\tChannel 1 (mV)\tChannel 2 (mV)\tChannel 3 (mV)\tChannel 4 (mV)\tChannel 5 (mV)\tChannel 6 (mV)\tChannel 7 (mV)\tChannel 8 (mV)\tChannel 1_cal (mg/L)\tChannel 2_cal ()\tChannel 3_cal ()\tChannel 4_cal ()\tChannel 5_cal ()\tChannel 6_cal ()\tChannel 7_cal ()\tChannel 8_cal ()\tMotor 1 (mm)\tMotor 2 (mm)", 
    @"\\tChannel [0-9]* \(mV\)"
).Groups[0].Captures.Count;

}
}