20850 Flight Qualified Heat Flux Transducers

Product Details

Medtherm 20850 Series Heat Flux Transducers are a family of total heat flux transducers and infrared radiometers qualified for space and missile flight in very difficult shock, vibration, and thermal environments.

20850 Series use a Schmidt-Boelter thermopile type sensor in 0 to 800 Btu/(ft²sec) ranges. Heat flux is absorbed at the sensor surface and is transferred to an integral heat sink that remains at a different temperature than the sensor surface. The difference in temperature between two selected points along the path of the heat flow from the sensor to the sink is a function of the heat being transferred, and a function of the net absorbed heat flux. At two such points, the transducer has thermopiles to form a differential thermoelectric circuit, thus providing a self-generated EMF at the output leads that is directly proportional to the heat transfer rate. No power supply or thermoelectric reference junction is needed.

20850 Series have passed the design, qualification test, acceptance test and flight experience requirements of Aerojet Strategic Propulsion Company Specification SPC-32317 and Drawing 1179142 on the SICBM program and has been flown on the several programs. Test reports are on file.

20850 Series Overview
Part Number Configurations

20850 Series Overview

Type I Schmidt-Boelter thermopile total heat flux transducer provides a linear EMF output directly proportional to the net absorbed heat flux to the sensing tip (typically cold wall flux),
Type II and VI Schmidt-Boelter thermopile infrared radiometers provide a linear EMF output directly proportional to the incident radiation which is within the passband of the chosen window.
Type I, II, and VI full scale output is 43±7 millivolts at the maximum design heat flux level.
Type III slug calorimeter provides a Type K thermocouple output with net absorbed heat flux determined from the slope of the thermocouple output versus time.
Each unit is supplied with an individual calibration traceable to the National Institute of Standards and Technology.

Medtherm 20850 Heat Flux Transducer

20850 Series Part Numbers

Below are the existing 20850 Heat Flux part number configurations available.

Part No.	Aerojet 58339SOCN	Type	Range (Btu/ft²sec)	Sensor	Window
20850-01	1179142-1	I	0 – 5	Total	‑
20850-02	1179142-2	I	0 – 8	Total	‑
20850-03	1179142-3	I	0 – 10	Total	‑
20850-04	1179142-4	I	0 – 13	Total	‑
20850-05	1179142-5	I	0 – 15	Total	‑
20850-06	1179142-6	I	0 – 35	Total	‑
20850-07	1179142-7	I	0 – 50	Total	‑
20850-08	1179142-8	I	0 – 200	Total	‑
20850-09	1179142-9	I	0 – 300	Total	‑
20850-10	1179142-10	II	0 – 2	Radiometer	Sapphire
20850-11	1179142-11	II	0 – 10	Radiometer	Sapphire
20850-12	1179142-12	III	0 – 100*	Slug	‑
20850-13	1179142-13	I	0 – 75	Total	‑
20850-14	1179142-14	I	0 – 20	Total	‑
20850-15	1179142-15	VI	0 – 10	Radiometer	Zinc Selenide
20850-16		II	0 – 35	Radiometer	Sapphire
20850-17		I	0 – 500	Total	‑
20850-18		IV	0 – 800	Total	‑
20850-19		I	0 – 100	Total	‑
20850-20		II	0 – 25	Radiometer	Sapphire
20850-21		II	0 – 75	Radiometer	Sapphire
20850-22		II	0 – 15	Radiometer	Sapphire
20850-23		II	0 – 5	Radiometer	Sapphire

*40 Btu/ft2 total integrated flux over time

Notes: Lead wire for Type I, II, and IV is M27500-24NF-2N12 with color code as tan wire positive, tan with dark stripe negative. Lead wire for Type III is 30 AWG ISA Type K solid conductor duplex with polyimide insulation over each, polyimide jacket overall, with color code as amber wire positive, amber with red stripe negative. An alternate Type III color code is yellow positive(+) and red negative(-). An alternate lead wire for Type I, II, and IV is M27500-24NG-2511.