Cooper-Atkins 5028 Slim Thermistor Temperature/Humidity Air Probe, 4.9″ Shaft Length Review January 4, 2018 No Comments Measure Relative Humidity with SRH77A. Features slim 1/4″ diameter shaft for easy insertion in ducts. Tags: Cooper, Home & Kitchen, Kitchen & Dining, Kitchen Utensils & Gadgets, Thermometers & Timers