tweak tangent divisor

docs/ziegler_tuning.md

@@ -71,7 +71,7 @@ The red diagonal line: this **must** follow the smooth part of your chart closel
 You might need to adjust the line parameters to make it fit your data properly. You can do this as follows:
 
 ```
-python kiln-tuner.py zn zn.csv --tangentdivisor 8
+python kiln-tuner.py zn zn.csv --tangentdivisor 4
 ```
 
 `tangentdivisor` modifies which parts of the profile is used to calculate the line.

kiln-tuner.py

@@ -183,7 +183,7 @@ if __name__ == "__main__":
     parser_zn = subparsers.add_parser('zn', help='Calculate Ziegler-Nicols parameters')
     parser_zn.add_argument('csvfile', type=str, help="The CSV file to read from. Must contain two columns called time (time in seconds) and temperature (observed temperature)")
     parser_zn.add_argument('--showplot', action='store_true', help="If set, also plot results (requires pyplot to be pip installed)")
-    parser_zn.add_argument('--tangentdivisor', type=float, default=4, help="Adjust the tangent calculation to fit better. Must be >= 2.")
+    parser_zn.add_argument('--tangentdivisor', type=float, default=8, help="Adjust the tangent calculation to fit better. Must be >= 2 (default 8).")
     parser_zn.set_defaults(mode='zn')
 
     args = parser.parse_args()