if (msg.topic === "tempf") {
    context.set('tempf',msg.payload);
} else if (msg.topic === "humidity") {
    context.set('humidity',msg.payload);
}

var tempf   = context.get('tempf');
var humidity = context.get('humidity');

// Quelle: https://www.chemie-schule.de/KnowHow/Taupunkt
// Gültigkeitsbereich Taupunkt:    -30°C <= tmp <= 70°C
var tp = ((241.2 * Math.log(humidity/100)) + ((4222.03716 * tempf) / (241.2 + tempf))) / (17.5043 - Math.log(humidity/100) - ((17.5043*tempf)/(241.2+tempf)));
tp = Math.round( tp * 100 ) / 100;
flow.set("flowtp",tp);
msg.payload = tp;
msg.topic = "Taupunkt";
return msg;