A system comprising an ultraviolet sensor (106, 306): and a controller (104, 404); the controller includes an adjustable voltage supply and a sense circuitry, a memory and a processor; the controller is configured to determine failure of the UV sensor (106, 306); the sense circuitry is configured to determine a UV event that has occurred when the UV sensor is in the presence of UV emissions; the adjustable voltage supply is configured to supply an excitation voltage to the UV sensor (106, 306); the memory; and the processor is configured to execute executable instructions stored in the memory to: reduce the excitation voltage of the UV sensor (106, 306) until no conduction occurs in the UV sensor (106, 306), the UV sensor having a UV tube, electrodes and a fill-gas composition; increase, upon no conduction occurring in the UV sensor (106, 306), the excitation voltage of the UV sensor (106, 306) until a conduction event occurs; compare the excitation voltage at which the conduction event occurs to a reference voltage; and determine whether the UV sensor (106, 306) has failed based on the comparison, wherein the reference voltage is a reference voltage range, and wherein the UV sensor (106, 306) is determined to have failed upon the excitation voltage at which the conduction event occurs being outside the reference voltage range, the reference voltage range is based on a construction of the UV sensor, including changes in a position of electrodes, a composition of the fill gas, and a pressure within the UV tube of the UV sensor wherein the excitation voltage at which the conduction event occurs is logged, and an average excitation voltage over a sample size of measurements of conduction events is compared to the reference voltage range. and a controller (104, 404); the controller includes an adjustable voltage supply and a sense circuitry, a memory and a processor; the controller is configured to determine failure of the UV sensor (106, 306); the sense circuitry is configured to determine a UV event that has occurred when the UV sensor is in the presence of UV emissions; the adjustable voltage supply is configured to supply an excitation voltage to the UV sensor (106, 306); the memory; and the processor is configured to execute executable instructions stored in the memory to: reduce the excitation voltage of the UV sensor (106, 306) until no conduction occurs in the UV sensor (106, 306), the UV sensor having a UV tube, electrodes and a fill-gas composition; increase, upon no conduction occurring in the UV sensor (106, 306), the excitation voltage of the UV sensor (106, 306) until a conduction event occurs; compare the excitation voltage at which the conduction event occurs to a reference voltage; and determine whether the UV sensor (106, 306) has failed based on the comparison, wherein the reference voltage is a reference voltage range, and wherein the UV sensor (106, 306) is determined to have failed upon the excitation voltage at which the conduction event occurs being outside the reference voltage range, the reference voltage range is based on a construction of the UV sensor, including changes in a position of electrodes, a composition of the fill gas, and a pressure within the UV tube of the UV sensor wherein the excitation voltage at which the conduction event occurs is logged, and an average excitation voltage over a sample size of measurements of conduction events is compared to the reference voltage range. reduce the excitation voltage of the UV sensor (106, 306) until no conduction occurs in the UV sensor (106, 306), the UV sensor having a UV tube, electrodes and a fill-gas composition; increase, upon no conduction occurring in the UV sensor (106, 306), the excitation voltage of the UV sensor (106, 306) until a conduction event occurs; compare the excitation voltage at which the conduction event occurs to a reference voltage; and determine whether the UV sensor (106, 306) has failed based on the comparison, wherein the reference voltage is a reference voltage range, and wherein the UV sensor (106, 306) is determined to have failed upon the excitation voltage at which the conduction event occurs being outside the reference voltage range, the reference voltage range is based on a construction of the UV sensor, including changes in a position of electrodes, a composition of the fill gas, and a pressure within the UV tube of the UV sensor wherein the excitation voltage at which the conduction event occurs is logged, and an average excitation voltage over a sample size of measurements of conduction events is compared to the reference voltage range.