Weiss Instruments is the leader Inch solar powered technology as we now offer seven different versions of our digital thermometers. Available in low light version 56SD, (15 Lux) 25SD, 72SD, (30 Lux) and Series 20SD (75 Lux). These "self powered" thermometers operate without any batteries and offer an attractive and modern update to existing refrigeration equipment. Each thermometer has adjustable calibration, a ten second update time and wide ambient temperature specifications for both indoor and outdoor installations.