Water Bath Digital - PSU Base. The unit, based on a Gratnells deep tray, uses a high-quality silicon 500W heat mat housed within a metal shell to deliver homogenous heating without the need for a stirrer. The digital temperature controller maintains the temperature to within 1°C up to 100°C and has a lock facility to prevent pupil tampering. Safety is maintained by an electronic water level sensor which automatically cuts off the power if the water level drops below a pre-set level. H 150mm, W312mm, D417mm, Weight 3.8kg. 5 year warranty. The water bath comes complete with full instructions and a Z-type test tube rack.