For best control, the moisture content of the furnace atmosphere needs to be continually monitored, so the hygrometer used must be capable of showing changes accurately and quickly.
Michell's S8000RS uses the chilled-mirror technology, which is the most accurate and reliable method to monitor dew-point because it measures the actual formation of moisture or frost on a temperature-controlled mirror, rather than relying on calculated values.
The S8000RS's advanced dual optics system detects minute changes in moisture condensed on the mirror surface, resulting in very high sensitivity (±0.01°C) when making measurements at low levels of moisture content. Because of the high temperatures involved, the sample gas is extracted from the furnace and passed through a cooling coil to bring it back down to ambient temperature for safe measurement.
Typically, the dew-point required for optimum performance in an annealing furnace is between -70 and -50°C, depending on the type of metal being treated and the end results required. This is well within the range of S8000RS, which has a measurement range of -80 (or -90, depending on the model) to +20°Cdp.
The S8000 RS has an intuitive interface, offers user selectable measurement units and has three analogue outputs as standard.
Other features include internal datalogging to an SD card and a USB connection. The instrument is supplied with a traceable calibration as standard, but an optional UKAS (United Kingdom Accreditation Service) accredited calibration is also available.