Background technology
The photoelectric sensor being applied to the instrument such as flow cytometer, chemical illumination immunity analysis instrument at present mainly uses photoelectricity
Multiplier tube.The photomultiplier tube way of output is divided into impulse type output and current mode to export two kinds, the most corresponding photomultiplier tube
Positive high voltage and negative high voltage type of drive.
Photomultiplier tube counting usage is widely used in enzymatic chemical luminous immunoassay instrument, but for exciting light light intensity
Relatively strong, occasion that out-put dynamic range is wide is the most inapplicable.Photomultiplier tube negative high voltage usage (plus earth) sensitivity is relatively
Low, dynamic range is wider, it is adaptable to the application that light intensity is stronger.Photomultiplier tube negative high voltage usage principle is as it is shown in fig. 7, anode is born
Carrying resistance RL and be typically translation circuit itself, RL is logafier in this application.
Classical signal testing circuit uses linear amplifier, and linear amplifier sensitvity constraint is in analog-digital converter essence
Degree, op-amp noise and operational amplifier precision.Use segmentation amplification detection to add circuit coherence request, also improve
The requirement of software, and this method is the highest to amplifier prime noise requirements, add system cost.
The logarithmic compression characteristic using logafier can widen electric circuit inspection scope significantly, and signal detection sensitivity is not
It is limited to the precision of analog-digital converter again, can guarantee that the signal to noise ratio that Larger Dynamic range data is changed is suitable.But it is right to be also limited by
Number curve compresses, and in the case of input is less than certain numerical value, circuit output is negative saturated.Therefore sensitive during the low input of logafier
Spend height, sensor low value input range is required higher.Logafier concordance debugging difficulty, sensitive to using temperature.
Logafier is also referred to as logarithmic converter, logarithmic circuit.
Between logarithmic amplifying circuit compression curve individuality there is deviation in concordance, affects weak-signal measurement result.Photomultiplier transit
Pipe is in actual application environment, and when anode quiescent current is positioned at the OK range of loaarithmic curve, sensor differences can't be made
Logafier is become to bear saturated, less on output result impact.
Before the existing production technology of photomultiplier tube mainly uses home built method, and photomultiplier tube finished product, parameter without
Method accomplishes accurately to control, and between individuality, parameter differences is big.Can only be by production tube be screened, it is ensured that photomultiplier tube parameter model
Enclose.The mode of screening greatly reduces the yield rate of photomultiplier tube, adds cost.
Summary of the invention
For solving above-mentioned technical problem: the present invention proposes a kind of compensation system being applicable to current-output type photomultiplier tube
System, including: photomultiplier tube, transducer, described photomultiplier tube is connected with transducer, it is characterised in that: also include that there is height
The compensation circuit of resistance characteristic, described compensation circuit is connected in parallel with described photomultiplier tube, it is possible to output bipolar offset electric current,
Described compensation size of current matches with described photomultiplier tube, transducer.
Preferable, described compensation circuit includes variable current source, and the output of this current source has double-polarity control ability.
Constant temperature and band electromagnetic shielding applied environment make described compensation circuit stability.
Preferable, described photomultiplier tube includes current-output type photomultiplier tube, i.e. negative high voltage usage, described photoelectricity
Multiplier tube gain includes fixed gain or adjustable gain;Described photomultiplier tube includes photomultiplier tube single tube or photomultiplier transit
Tube module.
Preferable, described switch input is electric current input, and the input electromotive force of transducer is close or equal to amplifying
Circuit reference earth potential;Described transducer includes the field that logafier or amplifying circuit are high to transducer dwell current requirements
Close.
Input amplifier electromotive force close to amplifying circuit with reference to ground, so electric current equal to reference source and be applied to high level
The electric current that resistance produces.
Preferable, described transducer is a kind of input and the circuit that output characteristic curve is loaarithmic curve, utilizes described
Transducer can widen the dynamic range of signal deteching circuit, and accuracy of detection is not by precision of A/D converter in the wide dynamic range mode
Impact.
Preferable, described compensation circuit includes adjustable voltage source and high value resistor, described adjustable voltage source
Including reference voltage source and potentiometer, described adjustable voltage source is carried out dividing potential drop regulation, dividing potential drop by potentiometer to reference power source
It is transported to the anode of photomultiplier tube afterwards by high value resistor, photomultiplier tube is carried out current compensation.
Preferable, described reference voltage source is the power supply of the most positive and negative two polarity, described potentiometer and said two
The power series of polarity, the power supply intermediate connection point ground connection of said two polarity.
The individual difference of photomultiplier tube quiescent current output is relatively big, compensates circuit offer and compensates electric current, with photomultiplier tube
Quiescent current superposition, so that the input of logarithmic amplifying circuit quiescent current is constant, reaches to select logafier proper operation district
Between purpose.
Ensure that system operates in constant temperature, in the environment of electromagnetic shielding.First regulation photomultiplier tube sensitivity is consistent.Lead to again
Cross Theoretical Calculation regulation or manually regulation compensate circuit, it is ensured that unglazed according to time the output of multiple photomultiplier tubes consistent, and output exists
Logarithmic amplifying circuit proper operation is interval.
The application provides a kind of immunity analysis instrument, comprises above-mentioned signal detection and compensates circuit or compensation method.
Detailed description of the invention
Below in conjunction with the accompanying drawings the present invention is described in further detail, it is necessary to it is pointed out here that, implement in detail below
Mode is served only for being further detailed the present invention, it is impossible to be interpreted as limiting the scope of the invention, this field
The present invention can be made some nonessential improvement and adjustment according to above-mentioned utility model content by technical staff.
Below in conjunction with accompanying drawing, embodiments of the present invention is further illustrated.
Chemical luminescence method immune analysis instrument, in the case of photomultiplier tube high voltage supply is 850V, signal high value photoelectricity
Multiplier tube maximum output current is about 200uA;But in low value blank solution, photomultiplier tube maximum output current only has 1nA.
Testing circuit sensitivity:
Sensor out-put dynamic range is 106dB, and therefore sensor detection circuit detection range should be more than 106dB.Make
Using conventional linear change-over circuit, accuracy of detection is confined to precision of A/D converter.24 analog-digital converter theoretical maximum can only reach
To 144.5dB dynamic range, it is meant that inputting blank solution when, system has the precision of 38.5dB, immunity analysis instrument is permitted
Many test events low value is significant for clinical diagnosis, and small-signal is easily disturbed, and is unfavorable for transmission.Therefore linear transformation
Circuit inapplicable native system.
The application is front lower in the premise of wide dynamic range detection technique, and current wide dynamic range signals detection method mainly has
Segmentation detection method and logarithmic transformation method.Segmentation detection method is accomplished completely the same due to multiple amplifier difficulties, and simultaneously drives multiple
Many changers of ADC can bring more large overhead to software, also increases hardware cost.Logarithmic transformation method advantage of lower cost, at mould
Intend front end and carry out Logarithm conversion, be conducive to improving circuit signal to noise ratio.After AD conversion, then digital algorithm is used to carry out index change
Change commanders signals revivification.The easy temperature influence of logafier, so needing design temperature to compensate circuit, and isoperibol work
Make.Temperature is bigger on the impact of photomultiplier tube dark current, so systematic survey unit uses isoperibol.
Fig. 1 is that logarithmic amplifying circuit is applied to wide dynamic range detection application.Including current mode photomultiplier tube 1, logarithm
Amplifier 2.
The logarithmic compression characteristic using logafier can widen electric circuit inspection scope significantly, and signal detection sensitivity is not
It is limited to the precision of analog-digital converter again, can guarantee that the signal to noise ratio of data conversion is suitable in the range of Larger Dynamic.Input-output characteristic
As shown in Figure 2.
Logafier input-output function in present case is: Y=0.582*ln (X)+6, Y in above-mentioned formula be right
Number amplifier output voltage units be V, X be input current unit uA.When X is less than 3.335*10-5uA, it is output as negative value, when
When the Acquisition Circuit that logafier rear end connects is unipolarity work, it is desirable to input is more than 3.335*10-2nA.And logarithm puts
Big device is in the case of input is the least, and circuit sensitivity is high.Photomultiplier tube is easily by external interference, such as magnetic field, temperature shadow
Ringing output, exporting the lowest when, the highest meeting of logafier sensitivity causes output pulsation bigger.Logafier exports
Voltage is positive and negative when beating back and forth, can increase back end signal and process circuit requirement.And find in actual applications, immunoassay system
Low value detection be not required to so high sensitivity, the too high meeting of transducer sensitivity brings unstable factor.
Patent CN102012370A proposes a kind of Circuits System improving atomic fluorescence detection performance and implementation method, should
Method, by increasing a current compensator, changes the reference potential of amplifier, and and photomultiplier tube by regulation compensator
Keep balance at blank solution background and veiling glare signal, make to be output as zero.Thus improve circuit sensitivity.But the method is not
Being applicable to native system, because in immunity analysis instrument, instrument blank solution background is affected by reagent lot, and blank solution background signal is not
Stable.And blank solution background is the lowest, there is not the feature that veiling glare in atomic fluorescence is bigger.In immunity analysis instrument, output letter
Number dynamic range is relatively big, and linear amplifier is difficult to wide dynamic range signals detection.
The compensation circuit mentioned in the compensatory approach mentioned in patent CN102012370A, compensation method block diagram such as Fig. 6 institute
Show.Circuit is really a voltage differential amplifier, and scheme changes operational amplifier input in the same direction by potentiometer and compensates electricity
Gesture Vb, so that output Vo=A × (Vi-Vb), wherein Vi is photomultiplier tube output voltage, and A is circuit amplification.
The PMT negative high voltage usage that this programme uses, therefore PMT anode is output as electric current output.Logafier needs to make
By transistor PN junction logarithm C-V characteristic, so logafier is electric current input.Preamplifying circuit carries out many primary currents electricity
Pressure conversion can increase circuit noise, and uses multiple amplifier can increase systematic error.Patent CN102012370A proposes
Compensation method is applicable to voltage model circuit, and inapplicable and native system.
According to problem present in above-mentioned, therefore this application provides a kind of compensation method, may be used for stable logarithm and put
Big device output area.
If Fig. 3 is the application solution principle block diagram, including photomultiplier tube 3, compensate circuit 4, logafier 5.Such as figure
Shown in the output of photomultiplier transit tube anode be connected to logafier input, compensate circuit output and logafier input
Be connected, i.e. photomultiplier tube output, logafier inputs, and compensates circuit output and is connected in same node.
Compensating circuit is a variable constant current source, and constant-current circuit is as shown in Figure 4.Constant-current source includes: adjustable voltage source
7, high value resistor 8.Adjustable voltage source comprises reference voltage source 6 and potentiometer 7, and adjustable source is electric to reference by potentiometer
Source dividing potential drop produces.Constant-current source needs have bipolar offset ability, when photomultiplier tube dark current less than Design of Amplification Circuit
During low input, constant-current source provides the electric current that direction is consistent with the PMT sense of current.When photomultiplier tube dark current is more than amplifying circuit
Time minimum, constant-current source provides the compensation electric current contrary with the PMT sense of current.Therefore potentiometer two ends need to connect positive and negative two polarity
Power supply.
The effect of high value resistor is that the voltage signal of adjustable voltage source is converted to current signal, due to logarithmic amplification
Circuit input end electromotive force close to amplifying circuit with reference to earth potential, so compensate electric current equal to adjustable voltage source and be applied to height
The electric current that value resistance produces.Owing to the resistance value of high value resistor is much larger than potentiometer resistance value, so potentiometer slip terminal
Voltage can be equivalent to variable voltage source.High value resistor ensure that signal input part input impedance is consistent, also embodies current source
High resistant characteristic.The circuit of the application ensures that photomultiplier tube, in the case of gain is the same, inputs the Static Electro of logafier
Stream is consistent.Compensation electric current isV in formulaBFor potentiometer sliding end voltage, RBFor high value resistor resistance.
In actual use, PMT running voltage is between 850~900V, and PMT obtains higher low value in immunoluminescence system
Sensitivity and sufficiently wide dynamic range.Logafier output voltage is when 1.2V, and circuit can obtain preferable stability
And detection sensitivity, now logafier input is 0.262nA.
Logafier compression ratio is the logafier differential of function, so the logafier compression ratio that this programme uses
For:When input is for 0.262nA, logafier sensitivity still has 2.22V/nA, the precision side of fully meeting
Case requirement.
Logafier input current: IAMP=IPMT-IB, wherein IAMP is logafier input current, and IPMT is light
Electricity multiplier tube fixed gain dark current, IBIt is to compensate circuit compensation electric current.
When PMT works at 850V, it is assumed that now PMT dark current is output as 0.8nA, then need to compensate 0.538nA electric current.
Compensating resistance is 1G Ω, then need to regulate adjustable reference source and can make logafier Static output 1.2V to 0.538V;Assume this
Time PMT dark current be output as 0.12nA, then need compensate-0.142nA electric current.Compensating resistance is 1G Ω, then need to regulate adjustable
Reference source can make logafier Static output 1.2V to-0.142V.
Logafier is when photomultiplier tube maximum output 200uA, and circuit sensitivity is 2.91 × 10-6V/nA.And
When blank reagent signal output 1.262nA, circuit sensitivity is 0.461V/nA.Minimum and maximum sensitivity difference 1.58 ×
105Times, logafier utilizes loaarithmic curve compression property, it is ensured that in wide dynamic range, signal sensitivity is with signal intensity
Increase and reduce.Logafier ensure that analog-digital converter error and signal intensity belong to same order, and therefore logarithm is put
Big device is widely used in wide dynamic signal detection.
The application workflow is as it is shown in figure 5, first regulation gain of photomultiplier is consistent;Regulate photomultiplier tube again to mend
Repay electric current, select logafier proper operation interval;Photomultiplier tube output signal Logarithm conversion is also converted to digital signal;
Carrying out exponential transform by MCU again, exponential transform is the inverse process of circuit logarithmic compression, and it is linear for can making signals revivification.Refer to
Transformation of variables formula is as follows, and in formula, e is the nature truth of a matter.X is PMT logafier input current, unit uA.Y is that logarithm is put
Big device output voltage, unit V.
Exponential transform formula is as follows:Apparatus measures result needs background subtraction signal to obtain solution to send out
Light intensity, background signal is apparatus measures unit background spurious optical signal value, needs in the acomia light moment, to PMT output signal
Take multiple somes meansigma methodss.
The application application circuit regulation process is as follows: ensureing under external environment constancy of temperature, use constant light source and
It is consistent that pico-ampere table adjusts multiple PMT sensitivity.
PMT is installed in dark situation, it is ensured that external environment temperature constant, treats that PMT output is stable, use pico-ampere table to measure
PMT exports electric current, and by calculating compensation size of current.Compensate circuital current size by result of calculation regulation again, make
Compensation circuital current size is mated with PMT thus is reached to reduce the purpose of PMT individual variation.
Can also manually select to compensate circuital current size by regulative mode.In the PMT constant situation of working environment environment
Under, sensor output is positioned at the specific operation interval of logafier.
Embodiment described above only have expressed the several embodiments of the present invention, and it describes more concrete and detailed, but also
Therefore the restriction to the scope of the claims of the present invention can not be interpreted as.It should be pointed out that, for those of ordinary skill in the art
For, without departing from the inventive concept of the premise, it is also possible to make some deformation and improvement, these broadly fall into the guarantor of the present invention
Protect scope.Therefore, the protection domain of patent of the present invention should be as the criterion with claims.