It will ensure the integrity of the cells against catastrophic freezing, which can break the glass envelope. Cooling is accomplished by efficient solid-state Peltier chilling modules, powered so that the rate of temperature change is very small. Two safety circuits are provided to prevent cell breakage by excessive ice formation. If control fails in such a mode that the Peltier chillers are full on, a warning light is lit to give the operator 20 minutes in which to take appropriate action. If no action is taken, the apparatus is automatically switched off and the cells are allowed to warm slowly.
Passive safety is provided by the physics of ice.
If the Peltier chillers become too cold, the first ice which forms is on the water tank surfaces directly in contact with the chillers, effectively inhibiting further rapid transfer of freezing to the bath water. A specific stirring rate of bath fluid is provided by bubble agitation which prevents the water from stratifying. The bath is manufactured to the strict requirements of BS 5750 and ISO 9000. It is released only when Isotech is entirely satisfied with its performance. The bath has a long and successful history and is relied on by many National Laboratories throughout the world.