Instrument for analyzing biological samples and reagents

A dispensing assembly comprising:

• a gantry with an x-axis track and a y-axis track, the y-axis track of the gantry configured to move along the x-axis track of the gantry;
• a dispensing head attached to and configured to move along the y-axis track of the gantry, the dispensing head comprising:
• a first z-axis track;
• a second z-axis track;
• a contact dispensing unit attached to an configured to move along the first z-axis track, the contact dispensing unit comprising one or more pipette tips;
• and
• a non-contact dispensing unit attached to and configured to move along the second z-axis track, the non-contact dispensing unit comprising a plurlity of jet tips and respective valves;
• a dispensing enclosure attached to the y-axis track of the gantry, the dispensing enclosure having a pressure reservoir, a metering pump for pressurizing the pressure reservoir to provide a constant pressure, and electronics configured to actuate the respective valves of the non-contact dispensing unit for dispensing;
• and
• one or more tubes connecting respective jet tips of the non-contact dispensing unit to the pressure reservoir of the dispensing enclosure.