Thermopiles are thermocouples arrays that are wired in series and used in motion sensing applications. They are relatively simple in design and are built to perform non-contact temperature measurements. Thermopiles or thermocouple arrays are thermal flux meters that consist of a thin, continuous layer of conductor and semiconductor material. Typically, this material is covered on one or more surfaces with a thin deposit of copper. A 32 x 32 array of tiny thermopiles senses thermal energy and detects infrared (IR) radiation. The remote measurement of multiple points allows the thermocouple array to build a multi-dimensional image. Thermopile sensors detect the absolute amount of emitted thermal energy and generate a proportional thermoelectric voltage. A thermopile sensor uses standard connectors and can measure a wide range of temperatures. Thermopiles are relatively inexpensive and often available as a thermopile detector.

Selecting Thermopiles

Metal type is an important consideration when selecting thermopiles. Base metal thermopiles can measure different temperature ranges, depending on the sensor material. Each type or designation represents a specific metal type and temperature range. Type E (chromel/constantan) has a typical temperature range of -270° C to 1000° C. Type J (iron/constantan) has a temperature range of -210° C to 1200° C. Type K (chromel/alumel) has a temperature range of -270° C to 1372° C. Type N (nicrosil/nisil) has a temperature range of -270° C to 1300° C. Type T (copper/constantan) has a temperature range of -270° to 400° C. For noble and refractory metals, choices include type B (platinum 30%/rhodium) with a temperature range of 0° C to 1820° C; Type S (platinum 10%/ rhodium) with a temperature range of -50° C to 1768° C; Type R (platinum 13%/rhodium) with a temperature range of -50° C to 1768° C; and Type W (tungsten/rhenium) with a temperature range of 0° C to 2300° C.