dbay

I am normaly working on automation project where I sometimes are using an algorithm from "Principles and Practices of Automatic Process Control" by Smith & Corripio. Perhaps some of you can use this quite simple aproach. I have only tried i out here in my workshop and i don't know if it will work in real life. But for me it seems to work fine. here is the Class: using System; using Microsoft.SPOT; /******************************************************************************** * Digital filter for noisy analogue signals. This equation is a standard * exponential filter taken from "Principles and Practices of Automatic Process * Control" by Smith & Corripio * * Equation: FltrPv = alpha * OldFltrPv + (1 - alpha) * RawPv * * where: * alpha = (tau / (tau + st)) * tau = time in sec for output to reach 63% of RawPv (Damping_time) * st = scantime, also update rate of equation * RawPv = variable to be filtered * FltrPv = filter variable * OldFltrPv = FltrPv (st - 1) ********************************************************************************/ namespace Netduino_PT100 { class Filter { const Int64 ticks_per_msec = System.TimeSpan.TicksPerMillisecond; float tau; float oldFltrPv; DateTime oldScantime = DateTime.Now; public Filter(float Tau = 10.0F) { tau = Tau; } public float Tick(float RawPv) { float st = (DateTime.Now.Subtract(oldScantime).Ticks / ticks_per_msec) * 0.001F; oldScantime = DateTime.Now; float alpha = (tau / (tau + st)); oldFltrPv = alpha * oldFltrPv + (1 - alpha) * RawPv; return oldFltrPv; } public void Set_tau(float Tau) { tau = Tau; } } } and here is the main program: using System; using System.Threading; using Microsoft.SPOT; using Microsoft.SPOT.Hardware; using SecretLabs.NETMF.Hardware; using SecretLabs.NETMF.Hardware.Netduino; namespace Netduino_PT100 { public class Program { public static void Main() { AnalogInput ain_1 = new AnalogInput(Pins.GPIO_PIN_A0); ain_1.SetRange(-40, 1040); Filter ain_1_filter = new Filter(); while (true) { Thread.Sleep(200); Debug.Print("Temperatur Filter:" + ain_1_filter.Tick(ain_1.Read() * 0.1F).ToString("N2")); Debug.Print("Temperatur Raw :" + (ain_1.Read() * 0.1F).ToString("N2")); } } } } /dennis

Unfortunately, as it's a joint endeavor (Atmel+Microsoft+Secret Labs) I don't know 100% for sure. We're _really_ close...but it's that last 1-10% that seems to take forever.

Chris

Hi all
Thangs for a great toy. Only missing one thing. Comms trougth the usb port.
Is there any news about this?

Dennis