The CellaTemp® PX 21 is a digital pyrometer with fibre-optic cable for measuring temperatures between 250 and 2000 °C. The pyrometer is equipped with a separate measuring cell. The pyrometer is equipped with a separate optical measuring head and a light guide. The fibre optics and measuring head are insensitive to interference from electromagnetic radiation and can be used in ambient temperatures up to 250 °C without cooling. The variant with separate optical measuring head has advantages especially in confined spaces.