Semi automatic fat testing machine operates on an input voltage of 230v ac with a frequency of 50hz and on a power consumption of 200watt. The fat testing machine works on an operating temperature range of 5° c to 45° c with an efficient battery back up and an in-built charger. The fat testing machine comes with an auto zero switching system and has the facility of automatic switch over to battery in case of power failure. Semi automatic fat testing machine enables high fat milk to be measured with improved accuracy and has a simple and easy operation.