A piston assembly , comprising: a piston ; and an anti-backlash device ; wherein the piston comprises: a diaphragm ; and a cavity for housing all or a substantial portion of the anti-backlash device ; and wherein the anti-backlash device comprises: a first nut having a first engagement feature and a first rotation locking feature , the first engagement feature structured for engagement with a lead screw of a motor , wherein the piston is coupled to the motor , and wherein the first nut is coupled to the piston and is fixed in relation to the piston ; a second nut having a second engagement feature and a second rotation locking feature , the second engagement feature structured for engagement with the lead screw , the second rotation locking feature structured to complement the first rotation locking feature for limiting or preventing relative rotation between the first nut and the second nut ; and a biasing member for maintaining a spaced relationship between the first nut and the second nut along the lead screw such that the first engagement feature of the first nut remains in engagement with the lead screw to thereby reduce or eliminate backlash when the lead screw is rotated by the motor in a first direction, the piston further comprising side opening for receiving set screws to prevent counter rotation or to prevent the first nut from backing out. a piston ; and an anti-backlash device ; wherein the piston comprises: a diaphragm ; and a cavity for housing all or a substantial portion of the anti-backlash device ; a diaphragm ; and a cavity for housing all or a substantial portion of the anti-backlash device ; and wherein the anti-backlash device comprises: a first nut having a first engagement feature and a first rotation locking feature , the first engagement feature structured for engagement with a lead screw of a motor , wherein the piston is coupled to the motor , and wherein the first nut is coupled to the piston and is fixed in relation to the piston ; a second nut having a second engagement feature and a second rotation locking feature , the second engagement feature structured for engagement with the lead screw , the second rotation locking feature structured to complement the first rotation locking feature for limiting or preventing relative rotation between the first nut and the second nut ; and a biasing member for maintaining a spaced relationship between the first nut and the second nut along the lead screw such that the first engagement feature of the first nut remains in engagement with the lead screw to thereby reduce or eliminate backlash when the lead screw is rotated by the motor in a first direction, a first nut having a first engagement feature and a first rotation locking feature , the first engagement feature structured for engagement with a lead screw of a motor , wherein the piston is coupled to the motor , and wherein the first nut is coupled to the piston and is fixed in relation to the piston ; a second nut having a second engagement feature and a second rotation locking feature , the second engagement feature structured for engagement with the lead screw , the second rotation locking feature structured to complement the first rotation locking feature for limiting or preventing relative rotation between the first nut and the second nut ; and a biasing member for maintaining a spaced relationship between the first nut and the second nut along the lead screw such that the first engagement feature of the first nut remains in engagement with the lead screw to thereby reduce or eliminate backlash when the lead screw is rotated by the motor in a first direction, <EOS>