The application based on and require that on 2 18th, 2016 U.S. Provisional Patent Application No.62/296,776's submitted is excellentIt first weighs, content is completely incorporated herein by reference.
Background technique
Online wet-chemical analysis instrument is for the continuous instruction in various industry with offer to the analyte in process sample.It shouldContinuous instruction can be provided locally by analyzer and/or be remotely supplied to one or more suitable equipment, in order to provideControl and/or monitoring to chemical process.
A kind of concrete type of online wet-chemical analysis instrument is online silica analyzer.These equipment are configured asReaction is generated in process sample, allows to determine the instruction of the silica in sample.This analyzer can be used for determining boilerDioxide-containing silica in water, boiler feedwater, softened water and steam condensate.Although this analyzer is to have in various industry, but they are particularly suitable for power plant boiler.In such systems, silica can form silicate deposit object,Turbine and other generating equipments used in water-steam turbine cycle may be damaged.Therefore, with the power generation of high-pressure turbineFactory usually carefully monitors silica, to ensure effectively detection and removal/reparation.One of online silica analyzerSpecific example is the trade name sold by Rosemount Analytical, Emerson Automation Solutions companyClaim the silica analyzer of model CFA3030.
Online silica analyzer will usually use known reaction, make it possible in easily detection process sampleSilica.One example of this reaction is referred to as molybdenum blue method.In the molybdenum blue method, molybdate (usually potassium molybdateForm) for the silicon dioxde reaction in process sample/solution, be suitable for the compound of colorimetric detection to generate.According to molybdenumBlue party method measures the dioxide-containing silica in water based on the color of the silicomolybdic acid formed by wet-chemical process.
Specific embodiment
This disclosure relates to a kind of light emitting diode (LED) for keeping constant irradiation level during temperature change.Various colorimetricsLight needed for wet-chemical analysis instrument generates colorimetric measurement using LED.LED generates light using the electron stream across p-n junction.When with constant current driven, the irradiation level of LED is the function of the temperature (i.e. the temperature of LED substrate (tube core)) of the environment of LED.It is especially true when LED emits the light of closer infrared light (IR) spectrum.In many cases, irradiation level these be based on temperatureThe variation of degree can be acceptable the user of LED.However, in some applications, such as colorimetric analyzer, this variationIt may cause measurement error.
When LED is used as the light source of colorimetric analyzer, the luminous intensity of light source with the temperature for the environment for placing analyzer andVariation.Absorptivity A is provided in following equation 1:
A=-log10 (I/I0) equation 1
Wherein I is the luminous intensity measured when color has shown after reacting, and I0It is to be surveyed before Color developmentThe luminous intensity of amount.During the operation of wet-chemical analysis instrument, luminous intensity this is measured occur at different times twice.IfEnvironment temperature changes during process and the if (I/I that LED with constant current driven, is measured0) calculating will include byError caused by dependence of the irradiation level to temperature.
Fig. 1 shows a part of colorimetric analyzer according to an embodiment of the present invention.Colorimetric analyzer 100 can be used for leading toCrossing makes illumination 104 pass through liquid 108 to analyze the liquid 108 for being located at and surveying in light unit 106.LED 102 is generated across liquid 108And the illumination 104 detected by optical sensor 110.Optical sensor 110 can be any sensor of the characteristic of detection light, including butIt is not limited to colorimeter, spectral radiometer, spectrophotometer or densitometer.
In order to compare the multiple measurement carried out by colorimetric analyzer 100, illumination 104 must be consistent.If between measurementsThere are the variations of illumination 104, then must be adjusted to the variation, and otherwise the comparison between measurement will be inaccurate.Show in Fig. 2AThe problem of having gone out LED.Chart 200 has the X-axis 202 for indicating temperature and indicates the Y-axis 204 of irradiation level.Trendline 206 is shownAs the temperature of LED increases, how the irradiation level of LED is reduced.
One solution of the problem is, if temperature changes, liquid 108 is discharged from survey light unit 106 and surveysNot blocked illumination 104 is measured as controlling value.Then, while keeping temperature, survey light unit is refilled with liquid 108106, illumination 104 was projected into liquid 108 and measurement experiment value.It is then possible to pass through controlling value regulation experiment value.This is a kind ofFeasible solution, but there is the cost for draining-refilling, and adjust measurement in 104 value of illumination based on variationA possibility that mistake is also increased during value.
A kind of better solution is, with temperature change, it is ensured that the illumination 104 generated by LED 102 is kept constant.The irradiation level of LED is not only determined by temperature.Fig. 2 B is to show irradiation level according to an embodiment of the present invention to the chart of electric current.Chart 250 has the X-axis 252 for indicating electric current and indicates the Y-axis 254 of irradiation level.Trendline 256 is shown with being supplied to LEDElectric current increase, how the irradiation level of LED to increase.It, can for the irradiation level for keeping constant LED in the temperature environment of variationTo change the electric current for being supplied to LED.For example, as temperature increases, the electric current also irradiation level by that must increase to keep constant.
Fig. 3 A shows LED circuit according to an embodiment of the present invention.LED circuit 300 includes LED 302, LED drive circuit304, feed circuit 308 and temperature sensor 306.Temperature sensor 306 is arranged to sense the temperature near LED 302.TemperatureDegree sensor 306 can be any suitable structure with the electrical characteristics varied with temperature.Example includes resistance temperature detectionDevice (RTD), thermocouple, thermistor etc..In one embodiment, temperature sensor 306 can use radiator and be couple to LED302 tube cores/substrate.
Temperature sensor 306 is couple to feed circuit 308, and feed circuit 308 provides signal to LED drive circuit 304.InsteadCurrent feed circuit 308 and/or driving circuit 304 may be implemented as any combination of number or analog circuit.For example, feed circuit308 can be used the microcontroller with analog-digital converter to realize, which receives from temperature sensor 306Signal simultaneously provides the digital indication of temperature.Then, which can be used to calculate by LED drive circuit 304 and adjustment mentionsThe power of LED 302 is supplied, to control irradiation level based on measured temperature.In one embodiment, LED drive circuit304 and feed circuit 308 be single circuit component.
Although implementation shown in Fig. 3 A is illustrated the temperature sensor 306 isolated with LED 302, it is expressly contemplated thatIt is that can practice a part or the embodiment being arranged in LED encapsulation that temperature sensor is LED 302.Fig. 3 B shows oneA embodiment, wherein LED drive circuit 304, feed circuit 308 and temperature sensor 306 are arranged in LED 302.However, thisAny one of a little components can be separated with LED 302.
Fig. 4 shows the flow chart of the method according to an embodiment of the present invention for LED control.Irradiation level stablizes 400 packetsInclude three steps.In frame 402, temperature is measured near LED.In one embodiment, temperature measurement is carried out in LED.
In frame 404, power adjustment is calculated.The calculating of power adjustment uses the temperature measured in frame 402 as input.?In one embodiment, which includes the temperature from manufacturer to irradiance data.In another embodiment, the calculating includesTemperature-the radiation constant being multiplied with the temperature of measurement.
In frame 406, the power of LED is adjusted to using the calculating from frame 404.It can be by with number and/or simulationCircuit that any combination of circuit is realized carries out the adjustment.It, can be with repetitive cycling simultaneously after adjustment is supplied to the power of LEDAnd the power of offer is continuously adjusted to compensate any temperature variation.
Although referring to preferred embodiment, invention has been described, it will be recognized by those skilled in the artIt is that without departing from the spirit and scope of the present invention, modification in form and details may be implemented.