A system for controlling flow of a liquid to a patient through use of an intravenous delivery system, the system comprising: a flow rate sensor that: measures a flow rate of the liquid through the intravenous delivery system; and generates a flow rate signal indicative of the flow rate; a controller that: receives the flow rate signal; compares the flow rate with a desired flow rate to determine that the flow rate is different from the desired flow rate; and in response to determining that the flow rate is different from the desired flow rate, transmits a control signal; and a flow rate regulator that: receives the control signal; and in response to receipt of the control signal, modifies the flow rate to bring the flow rate closer to the desired flow rate, characterized in that the flow rate sensor is secured to a drip unit of the intravenous delivery system, wherein the drip unit comprises a drip chamber and an orifice that delivers drops of the liquid from a liquid source to the drip chamber via gravity feed, wherein the flow rate sensor measures the flow rate by counting drops received by the drip chamber within a predetermined time period, and the system comprises the drip unit; wherein the drip unit comprises a key feature indicative of an orifice size of the orifice; wherein the flow rate sensor comprises a key feature receiver that receives the key feature in response to securement of the flow rate sensor to the drip unit; wherein the flow rate sensor uses the orifice size to determine the size of the drops and a volume of the liquid in each of the drops to facilitate measurement of the flow rate. a flow rate sensor that: measures a flow rate of the liquid through the intravenous delivery system; and generates a flow rate signal indicative of the flow rate; measures a flow rate of the liquid through the intravenous delivery system; and generates a flow rate signal indicative of the flow rate; a controller that: receives the flow rate signal; compares the flow rate with a desired flow rate to determine that the flow rate is different from the desired flow rate; and in response to determining that the flow rate is different from the desired flow rate, transmits a control signal; and receives the flow rate signal; compares the flow rate with a desired flow rate to determine that the flow rate is different from the desired flow rate; and in response to determining that the flow rate is different from the desired flow rate, transmits a control signal; and a flow rate regulator that: receives the control signal; and in response to receipt of the control signal, modifies the flow rate to bring the flow rate closer to the desired flow rate, receives the control signal; and in response to receipt of the control signal, modifies the flow rate to bring the flow rate closer to the desired flow rate, characterized in that the flow rate sensor is secured to a drip unit of the intravenous delivery system, wherein the drip unit comprises a drip chamber and an orifice that delivers drops of the liquid from a liquid source to the drip chamber via gravity feed, wherein the flow rate sensor measures the flow rate by counting drops received by the drip chamber within a predetermined time period, and the system comprises the drip unit; wherein the drip unit comprises a key feature indicative of an orifice size of the orifice; wherein the flow rate sensor comprises a key feature receiver that receives the key feature in response to securement of the flow rate sensor to the drip unit; wherein the flow rate sensor uses the orifice size to determine the size of the drops and a volume of the liquid in each of the drops to facilitate measurement of the flow rate.