Experiences in maintaining a stable variometer temperature in a small enclosure

Historically, geomagnetic observatories have housed variometer instruments in large volume, well-insulated buildings or enclosures. With the move from optically recorded instruments to digitally recorded modern fluxgate magnetometers, the requirements of the enclosure have also changed. No longer is it necessary to maintain such large volumes to the same accuracy of temperature and there is a potential for significant cost savings in scaling down the enclosure and using modern heaters and heating controllers to stabilise the temperature. BGS has conducted some initial tests on the suitability of heaters and heating controllers with the intention of then developing a small, easily deployable variometer enclosure to be used in place of existing observatory buildings, or for new observatories. However, small enclosures place the heaters, controllers and magnetometers in close proximity and here we show some of the problems encountered and solutions formed in these early stages of development.