A data acquisition system, including an input configured to receive a signal on a port and a processor. The processor determines, during an initial scan, a first measurement value of the signal on the port, sets at least one alarm value based on the first measurement value, the at least one alarm value being within a predetermined amount of the first measurement value, receives, during a subsequent scan, a second measurement value of the signal on the port, and generates an alert when the second measurement value violates the at least one alarm value.