Calibrating sensors

What are people doing to calibrate sensors? I have 4 different temp sensors that are sitting an inch away from each other and there is a 10 degree spread between them. What method are people using to calibrate temp sensors?

As for humidify I see about a 15% spread. So with those sensors I am going to do the salt calibration to 75% tonight and set the adjustment tomorrow.


i purchased a quasi ntsc calibrated temp/humidity sensor: