diff -r e2766e538d0e -r e00f8ff4de9a thermferm/pid.c
--- a/thermferm/pid.c	Mon Nov 04 13:19:27 2019 +0100
+++ b/thermferm/pid.c	Sat Apr 25 20:31:31 2020 +0200
@@ -1,5 +1,5 @@
 /*****************************************************************************
- * Copyright (C) 2015..2016
+ * Copyright (C) 2015..2020
  *   
  * Michiel Broek <mbroek at mbse dot eu>
  *
@@ -41,26 +41,26 @@
 {
     if (pid->Mode == PID_MODE_AUTO) {
 
-	double	dTerm;
+	double	dInput;
 
 	if (pid->Type == PID_TYPE_HEAT)
 	    pid->Err = pid->SetP - pid->Input;
 	else
 	    pid->Err = pid->Input - pid->SetP;
 
+	dInput = (pid->Input - pid->InputLast);
+
 	/*
 	 * Calculate the integral state with appopriate limiting.
-	 * Use ErrLastLast as iState
 	 */
 	pid->iState += (pid->iGain * pid->Err);
+	pid->iState -= (pid->pGain * dInput); // Add Proportional on Measurement
 	if (pid->iState > pid->iMax)
 	    pid->iState = pid->iMax;
 	else if (pid->iState < 0)
 	    pid->iState = 0;
 
-	dTerm = (pid->Input - pid->InputLast);
-
-	pid->OutP = (pid->pGain * pid->Err) + pid->iState - (pid->dGain * dTerm);
+	pid->OutP = pid->iState - pid->dGain * dInput;
 	pid->InputLast = pid->Input;
 
     } else if (pid->Mode == PID_MODE_BOO) {