Ultra-wide dynamic range differential conductivity detection circuit for ion chromatography

Abstract

A conductivity detection module for an ion chromatography system includes a detection cell configured to receive an eluent flow from the system, the detection cell having a first electrode and a second electrode that are in electrical contact with the eluent flow. A first current branch is connected to a first cell drive input and a first electrode to provide a first cell output; and a second current branch is connected to a second cell drive input and a second electrode to provide a second cell output. The first and second cell drive inputs are of equal magnitude but opposite signs.

Description

Technical Field

[0001] Cross-reference of related applications This application claims priority and benefit under 35 U.S.C. § 119(e) to U.S. Provisional Application No. 63 / 502,678, filed May 17, 2023, the disclosure of which is hereby incorporated by reference in its entirety for all purposes.

[0002] Cited by reference All publications, patents, and patent applications mentioned in this specification are hereby incorporated by reference as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference.

[0003] This disclosure relates to techniques including an ultra-wide dynamic range differential conductivity detection circuit for ion chromatography.

Background Art

[0004] Ion chromatography (IC) is a widely used analytical technique for measuring anions and cations in various samples. Conductivity detectors are often used in ion chromatography (IC) for detecting the anions and cations of interest.

[0005] Dynamic range can often be limited by the detection system. In some cases, the limitation of the detection system's dynamic range can be caused by the saturation of the analog-to-digital converter (ADC). For example, the resolution of a 16-bit analog-to-digital converter (ADC) is limited to a maximum of approximately 4.8 digits (log2^16). This is because a 16-bit ADC has a range of possible digital output values ​​from 0 to 65535. When using such components, it is usually necessary to adjust the gain of the detector, or the gain of the amplifier between the detector and the ADC input, so that the detector outputs a signal at the ADC input corresponding to multiple digital counts. This is to ensure that even small peaks are detected as at least one bit by the digital counter. Otherwise, small peaks below the threshold will not be recorded, resulting in errors in the measured intensity. In fact, the dynamic range of a 16-bit ADC is less than 4.8 digits. Typically, the effective dynamic range is about 3.9 digits. [Overview of the project] [Problems that the invention aims to solve]

[0006] There is a need to develop a high dynamic range detection and measurement system that can detect and measure signals across a wide range of intensities, from weak to strong, without being affected by saturation or a decrease in the detection threshold in the noise band. Furthermore, a detection and measurement system is needed that can operate in real time and achieve high-speed operation without being affected by saturation or a low detection threshold. There is a need for simpler methods and devices to extend the dynamic range while maintaining appropriate resolution. [Means for solving the problem]

[0007] In a first aspect of the present invention, a conductivity detection module for an ion chromatography system includes a detection cell configured to receive an eluent flow from the ion chromatography system. The detection cell includes a first electrode and a second electrode that are in electrical contact with the eluent flow. The conductivity detection module further includes a first current branch connected to a first cell drive input and the first electrode to provide a first cell output; and a second current branch connected to a second cell drive input and the second electrode to provide a second cell output. The first and second cell drive inputs are of equal magnitude and opposite sign.

[0008] In various embodiments of the first aspect, the detection cell does not have a ground electrode.

[0009] In various embodiments of the first aspect, the voltage applied to the detection cell is expressed as the difference between the first cell drive input and the second cell drive input.

[0010] In various embodiments of the first aspect, the first cell output and the second cell output correspond to the product of the current flowing through the detection cell and the gain.

[0011] In various embodiments, the ion chromatography system includes a conductivity detector module according to a first embodiment; a cell-driven DAC configured to provide a first cell-driven input and a second cell-driven input; and a cell-current ADC configured to convert the first and second cell outputs into digital outputs. In certain embodiments, the ion chromatography system further includes a control unit configured to compare the digital output with a signal range, the control unit configured to generate a cell-driven level signal based on the comparison and provide the cell-driven signal to the cell-driven DAC. In certain embodiments, the control unit is configured to compare the digital output with a cell-driven signal range, generate a cell-driven level signal based on the comparison and provide it to the cell-driven DAC, thereby maintaining the digital output of the cell-current ADC within the signal range.

[0012] In a second embodiment, a signal processing assembly for a conductivity detector in an ion chromatography system includes a cell drive DAC configured to provide a drive voltage to a detection cell, the voltage amplitude of which is based on a cell drive level signal. The detection cell is configured to receive an eluent flow from the ion chromatography system. The signal processing assembly further includes a differential cell drive and transimpedance amplifier circuit configured to amplify the output of the measurement cell, a cell current ADC configured to convert the output of the signal amplifier into a digital output, and a control unit configured to compare the digital output with a signal range; and a control unit configured to compare the digital output with a signal range, the control unit being configured to generate a cell drive level signal based on the comparison and to provide the cell drive level signal to the cell drive DAC.

[0013] In various embodiments of the second aspect, the control unit adjusts and generates a cell drive level signal to maintain the digital output within the signal range.

[0014] In each embodiment of the second aspect, the detection cell does not have a ground electrode.

[0015] In various embodiments of the second aspect, the detection cell includes a first electrode and a second electrode that are in electrical contact with the eluent flow; and the differential cell drive circuit and transimpedance amplifier circuit are as follows: a first current branch is connected to a first cell drive input and a first electrode from a cell drive DAC to provide a first cell output; and a second current branch is connected to a second cell drive input and a second electrode from a cell drive DAC to provide a second cell output. In certain embodiments, the voltage across the detection cell is expressed as the difference between the first cell drive input and the second cell drive input. In certain embodiments, the first cell output and the second cell output correspond to the product of the current flowing through the detection cell and the gain.

[0016] In a third aspect, the signal processing assembly for the conductivity detector of an ion chromatography system comprises the following configuration: A cell-driven DAC is configured to supply a voltage based on a cell-driven level signal, providing voltage drive to the detection cell. The detection cell is configured to receive the eluent flow from the ion chromatography system. A differential cell-driven and transimpedance amplifier circuit is configured to amplify the output of the measurement cell. A cell-current ADC is configured to convert the output of the signal amplifier into a digital output; and the control unit includes ADC data range scaling logic and filtering logic, the ADC range scaling logic operating to adjust the digital output of the cell-current ADC considering the range scaling applied to the cell-driven DAC by the cell-driven signal level; the filtering logic operating to reduce high-frequency noise, and the range scaling logic operating before the filtering logic.

[0017] In various embodiments of the third aspect, the control unit further comprises decimator logic that operates to reduce the sampling frequency, the decimator logic operating between range scaling logic and filtering logic.

[0018] In each embodiment of the third aspect, the control unit further includes a low-latency channel for comparing the digital output with the signal range, generating a cell drive level signal based on the comparison, and supplying the cell drive level signal to the cell drive DAC. In certain embodiments, the control unit generates a cell drive level signal to keep the digital output within the signal range.

[0019] In various embodiments of the third aspect, the detection cell includes a first electrode and a second electrode that are in electrical contact with the eluent flow; the differential cell drive and transimpedance amplification circuit includes a first current branch connected to the first electrode and receiving a first cell drive input from a cell drive DAC, providing a first cell output; and a second current branch connected to the second electrode and receiving a second cell drive input from the cell drive DAC, providing a second cell output. In certain embodiments, the voltage across the detection cell is the difference between the first cell drive input and the second cell drive input. In certain embodiments, the first cell output and the second cell output correspond to the product of the current flowing through the detection cell and the gain.

Brief Description of Drawings

[0020] [Figure 1] Figure 1 shows an exemplary ion chromatography system according to various embodiments.

[0021] [Figure 2] Figures 2, 3, and 4 show examples of detector circuits according to various embodiments. [Figure 3] Figures 2, 3, and 4 show examples of detector circuits according to various embodiments. [Figure 4] Figures 2, 3, and 4 show examples of detector circuits according to various embodiments.

[0022] [Figure 5] Figure 5 is a flowchart showing an exemplary method for measuring signals from a conductivity detector according to various embodiments.

Modes for Carrying Out the Invention

[0023] Here, embodiments of an ultra-wide dynamic range differential conductivity detection circuit for ion chromatography will be described.

[0024] The section headings used herein are for organizational purposes and do not limit the scope of the described content in any way.

[0025] In this paper, in the detailed descriptions of various embodiments, many specific details are provided for the sake of clarity and to enhance the understanding of the disclosed embodiments. However, those skilled in the art will understand that these various embodiments can be implemented with or without specific details. In other cases, structures and apparatus are shown in block diagrams. Furthermore, those skilled in the art will readily understand that the specific order in which the methods are presented and performed is merely illustrative, and that any changes in order will still fall within the spirit and scope of each embodiment disclosed herein.

[0026] All documents and similar materials cited herein (including, but not limited to, patents, patent applications, articles, books, professional texts, and web pages on the internet) shall be incorporated in their entirety for any purpose. Unless otherwise stated herein, all technical and scientific terms used herein shall have the meanings that would be commonly understood by a person skilled in the art in which each embodiment described herein pertains.

[0027] In these teachings, it should be understood that "approximately" implicitly precedes values ​​such as temperature, concentration, time, pressure, flow rate, and cross-sectional area. Therefore, even if a small deviation has virtually no effect, it is considered to be within the scope of these teachings. In this application, the use of the singular form includes the plural form unless otherwise specified. Similarly, the use of "comprise," "comprises," "comprising," "contain," "contains," "containing," "include," "includes," and "including" is not intended to be limiting. It should be noted that the above general description and the following detailed description are illustrative and explanatory only and do not limit the scope of the teachings of the present invention.

[0028] In this specification, "a" or "an" may also mean "at least one" or "one or more." Furthermore, the use of "or" is inclusive, and the expression "A or B" holds true if "A" is true, if "B" is true, or if both "A" and "B" are true. Unless otherwise required by context, singular terms shall be considered plural, and plural terms shall be considered singular.

[0029] A "system" is a set of elements that constitute a whole, whether tangible or abstract, in which each component interacts with or relates to at least one other component within the whole.

[0030] Figure 1 shows one embodiment of the chromatography system 100. The chromatography system 100 may include a pump 102, an electrolytic eluent generator 104, a continuously regenerating trap column 106, a degasser 108, a sample injector 110, a chromatography separator 112, an electrolytic suppressor 114, a detector 116, and a microprocessor 118. The chromatography separator 112 may be configured as a capillary column or an analytical column. Line 120 may be used to deliver liquid from the output of the detector 116 to the inlet of the electrolytic suppressor 114. Line 124 may be used to transfer liquid from the outlet of the regenerator channel of the electrolytic suppressor 114 to the inlet of the continuously regenerating trap column 106. A recirculation line 126 may be used to transfer liquid from the outlet of the continuously regenerating trap column 106 to the inlet of the degasser 108. Liquid from the outlet of the degasser 108 may be led to a waste line 128.

[0031] Pump 102 may be configured to deliver a liquid, such as deionized water, from a liquid source 132 and to be fluidly connected to an electrolytic eluent generator 104. Pump 102 may be configured to deliver the liquid at a pressure ranging from about 20 PSI to about 15,000 PSI. Under certain circumstances, pressures exceeding 15,000 PSI may be applied. Note that the pressures shown herein are given relative to ambient pressure (13.7 PSI to 15.2 PSI). Pump 102 may also be a high-pressure liquid chromatography (HPLC) pump. Furthermore, pump 102 may be configured so that the liquid comes into contact only with the inert portion of pump 102, thereby preventing a significant amount of impurities from leaching out. In this context, “significant” means an amount of impurities that would interfere with the intended measurement. For example, the inert portion may be made of polyether ether ketone (PEEK) or at least coated with a PEEK lining that does not leach a significant amount of ions when exposed to the liquid.

[0032] An eluent is a liquid containing an acid, base, salt, or a mixture thereof, which can be used to elute an analyte through a chromatography column. Furthermore, the eluent may include a mixture of a liquid and a water-miscible organic solvent, which may contain an acid, base, salt, or a combination thereof. The electrolytic eluent generator 104 is configured to produce a generalant. A generalant refers to a specific acid, base, or salt that can be added to the eluent. In some embodiments, the generalant may be a base such as a cationic hydroxide, or an acid such as carbonic acid, phosphoric acid, acetic acid, methanesulfonic acid, or a combination thereof.

[0033] Referring to Figure 1, the eluent generator 104 may be configured to receive liquid from the pump 102 and add genericant to that liquid. The liquid containing genericant may be supplied from the eluent generator 104 to the inlet of the continuously regenerating trap column 106.

[0034] The continuously regenerating trap column 106 is configured to remove cationic or anionic contaminants from the eluent. The continuously regenerating trap column 106 may include an ion exchange bed with an electrode at the eluent outlet. An ion exchange membrane stack may separate the eluent from the second electrode, and contaminating ions may be moved to the second electrode through the ion exchange membrane stack. The ion exchange membrane stack may include one or more ion exchange membranes. In various embodiments, anion removal may utilize an anion exchange bed with a cathode at the eluent outlet, separated from the anode by an anion exchange membrane. In various embodiments, anion removal may utilize an anion exchange bed with a cathode at the eluent outlet and separated from the anode by an anion exchange membrane.

[0035] The degasser 108 may be used to remove residual gases. In some embodiments, residual gases such as hydrogen or oxygen may be generated by electrolysis. The degasser 108 may include a gas-permeable and liquid-impermeable tubing section, such as an amorphous fluoropolymer, or more specifically, Teflon AF. A fluid from which most of the gas has been removed can be delivered from the degasser 108 to the sample injector 110.

[0036] A sample injector 110 may be used to inject a portion of a liquid sample into the eluent stream. The liquid sample may contain multiple chemical components (i.e., matrix components) and one or more target analytes. The sample injector 110 may include an autosampler 134, a sample loop 136, and a multiport valve 138. The autosampler 134 may take a sample from a sample container. The multiport valve 138 may be positioned in a first position to allow the sample to fill the sample loop 136. Once the sample loop 136 is filled to a predetermined level, the multiport valve is switched to a second position, and the sample can be introduced into the chromatography separation unit 112 by the eluent stream.

[0037] The chromatography separator 112 can be used to separate various matrix components present in a liquid sample from the target analyte. Typically, the chromatography separator 112 may take the form of a hollow cylinder filled with a stationary phase. As the liquid sample passes through the chromatography separator 112, the retention time of the matrix components and target analyte before elution from the chromatography separator 112 can vary. Depending on the properties of the target analyte and matrix components, they may exhibit different affinities to the stationary phase in the chromatography separator 112. The output of the chromatography separator 112 may be fluidically connected to an electrolytic suppressor 114.

[0038] The suppressor 114 can be used to reduce the conductivity background of the eluent and improve the response of the analyte by efficiently exchanging counterions of the eluent with regenerating ions. An electrolytic suppressor 114, a type of suppressor, may include an anode chamber, a cathode chamber, and an eluent suppression bed chamber separated by an ion exchange membrane. The anode chamber and / or cathode chamber may generate or transport regenerating ions. The eluent suppression bed chamber may include a channel for the eluent separated from the regenerator by an ion exchange barrier, and counterions of the eluent may exchange with regenerating ions via the ion exchange barrier. The outlet of the electrolytic suppressor 114 may be connected to a detector 116 through the channel to measure the presence of separated chemical components in a liquid sample. The suppressor 114 may be of a chemical type requiring a chemical regenerator. Any suppressor of the prior art, comprising multiple configured channels, is suitable for this application.

[0039] The detector 116 may take the form of an ultraviolet-visible spectrometer, a fluorescence spectrometer, a refractive index detector, a radioflow detector, a chiral detector, an electrochemical detector, a conductivity detector, or a combination thereof. Preferably, the detector 116 is a non-destructive detector, such as a conductivity detector, that substantially retains the eluent flow from the suppressor's eluent output.

[0040] The electronic circuitry may include a microprocessor 118, a timer, and a memory section. Furthermore, the electronic circuitry may include a power supply configured to apply control signals, respectively. The microprocessor 118 may be used to control the operation of the chromatography system 100. The microprocessor 118 may be integrated into the chromatography system 100 or be part of a personal computer communicating with the chromatography system 100. The microprocessor 118 may be configured to communicate with and control several components of the chromatography system, such as pumps 102, 130, eluent generator 104, sample injector 110, and detector 116. The memory section may be used to store instructions that set the magnitude and timing of the current waveform in response to the switching of the sample injector 110.

[0041] Figures 2 and 3 illustrate a technique for separating small peaks when using a conductivity detector by implementing a wide dynamic range and common-mode rejection. Even in the presence of large conductivity peaks, a large dynamic range and adaptive range are necessary to separate small conductivity peaks.

[0042] In ion chromatography detection, distinguishing small peaks when large peaks are present presents a challenge. One approach is to switch between different analog-to-digital converter (ADC) ranges to achieve the desired resolution. However, switching ranges introduces artifacts such as small peaks into the chromatogram. Furthermore, this problem is exacerbated by noise in the system.

[0043] Figure 2 is a block diagram showing an exemplary detection circuit assembly 200, which may function in place of all or part of the detector 116. The detector assembly 200 includes a cell-driven digital-to-analog converter (DAC) 202, a differential cell-driven and transimpedance amplifier 204, a cell-current ADC 206, and a digital controller 208.

[0044] The cell drive DAC 202 supplies a positive drive voltage 210 and a negative drive voltage 212 to the differential cell drive and transimpedance amplifier 204. The differential cell drive and transimpedance amplifier 204 supplies a positive output 214 and a negative output 216 to the cell current ADC 206. The output 218 of the cell current ADC 206 is used by a digital controller to adjust the cell drive DAC 202 via the cell drive level output 220.

[0045] The cell drive voltage DAC202 operates in conjunction with the cell current ADC206, achieving a wider dynamic range than the ADC206 alone can provide. The cell drive DAC202 fine-tunes to keep the current through the cell relatively constant, achieving an optimal signal-to-noise ratio at the input of the cell current ADC206, thereby providing smooth range changes.

[0046] Figure 3 shows a differential cell drive circuit and transimpedance amplifier circuit 300 (e.g., a differential cell drive circuit and transimpedance amplifier 204). The differential cell drive and transimpedance amplifier circuit 300 provides common-mode rejection, minimizing the impact of system noise on conductivity measurements. Such an implementation eliminates the effects of ground loops and DC conduction paths. The differential cell drive and transimpedance amplifier circuit 300 also doubles the usable cell drive voltage range for low conductivity measurements.

[0047] In the example shown in the figure, the differential cell drive and transimpedance amplifier circuit 300 is configured to receive the cell drive voltage from the DAC. The differential cell drive and transimpedance amplifier circuit 300 includes amplifiers 302, 304, a detection cell 306, 308, and 310. Amplifier 302 receives a positive cell drive voltage 312 at input 314. Due to negative feedback, the voltages at inputs 314 and 316 are the same. Amplifier 304 receives a negative cell drive voltage 318 at input 320. Due to negative feedback, the voltages at inputs 320 and 322 are the same. Therefore, the voltage across the detection cell 306 is the differential input DAC voltage (positive cell drive voltage 312 minus negative cell drive voltage 318). Due to the high impedance input of the operational amplifier, the current flowing through the detection cell 306 is the same as the current flowing through resistors 324 and 326. The outputs of amplifiers 302 and 304 are the voltage at the input terminal and the sum of the product of the sense cell current and resistor 324 or resistor 326. Amplifiers 308 and 310 provide an inverting summing circuit to remove the cell drive voltage. The outputs of amplifiers 308 and 310 represent the value obtained by multiplying the current of the sense cell 306 by the gain (gain = R1 = R2). Capacitors 328 and 330 compensate for the input capacitance. The differential cell drive and transimpedance amplifier circuit 300 can be divided into two symmetrical current branching sections 332 and 334.

[0048] In various embodiments, the digital controller 208 may include programmable logic (logic circuits) such as an FPGA. Figure 4 is a block diagram of an exemplary programmable logic 400. The programmable logic 400 may include a variable frequency modulator 402, a cell-driven DAC range scaling 404, a CD ADC control circuit 406, an SPI interface 408, a variable delay 410, a digital demodulator 412, a digital blanking 414, an ADC data range scaling circuit 416, a CIC filter and decimator 418, and a digital filter 420. The variable frequency modulator 402 can supply a modulation signal and adjust the frequency. The cell-driven DAC range scaling 404 can control the range scaling of the DAC, as described later. The CD ADC control circuit 406 can control the ADC. The SPI interface 408 can provide communication between the digital controller and other components such as the ADC and DAC. The digital demodulator 412 can demodulate the signal from the ADC. The ADC data range scaling circuit 416 can adjust the output of the ADC, taking into account the range scaling applied to the DAC. The CIC filter and decimator 418 can reduce the sampling frequency from 128 kHz to 100 Hz, and the digital filter 420 can remove high-frequency noise. Importantly, the ADC data range scaling circuit 416 is applied before the CIC filter and decimator 418, as well as the digital filter 420. This ensures that the CIC filter and decimator 418 and the digital filter 420 only process values ​​that are not affected by the range scaling.

[0049] Figure 5 shows an example of Method 500 for adaptive control of the detector's electrometer. At the start of step 802 of Method 500, the user or an automated routine is configured to pre-set the parameters of electronic equipment such as the detector circuit assembly 200. Pre-setting the parameters of the detector circuit assembly 200 may include determining or pre-defining a recommended dynamic input range based on the capabilities of the amplifier 204 and / or ADC 206, or setting the initial parameters of the DAC 202. Once the parameters of the detection circuit assembly 200 are pre-set, the chromatography system may be started in step 504 and configured to activate the detection circuit assembly 200 so that measurement result data can be continuously received. In step 506, the digital controller 208 is configured to receive the cell current input voltage 218 from the digital controller 208 and determine whether the input voltage 218 is within the desired operating range. In various ways, as described below, it may be possible to determine whether the current input voltage 218 is within the recommended operating range and automatically adjust the cell drive level output 220 accordingly. Users may be able to pre-set various thresholds for switching the cell drive level output 220.

[0050] In the first example, the digital controller 208 analyzes the ADC output over multiple cycles (e.g., 4 cycles) to obtain an average value and other similar signal characteristics. In various embodiments, the signal may be modulated at a modulation frequency of 4 kHz. Averaging four modulation cycles at a modulation frequency of 4 kHz results in a response time of 1 msec, but faster or slower response times can be obtained by changing the modulation frequency and the number of cycles used for averaging. If the average value falls below a lower threshold, for example, less than about 45% of the maximum value of a particular voltage input range, the cell drive level output 220 is moved to the next lower range. In various embodiments, the lower threshold may be less than about 40% of the maximum value of the current input voltage range, for example less than about 35%, less than about 30%, or even less than about 25%. Similarly, if the average value exceeds an upper threshold, for example more than about 85% of the maximum value of the current input voltage range, the input offset is moved to the next higher range. In various embodiments, the upper threshold may exceed about 90%, for example more than about 95% of the maximum value of a particular voltage input range.

[0051] In the second example, the digital controller 208 samples two voltage points Vp1 and Vp2 and analyzes the rate of change or trend of the signal (Vp1-Vp2) to predict the range in which future voltage points will be located. If the slope or trend rate is smaller than the previous value, it can be predicted that future voltage points will not deviate significantly from the existing range, and the input offset is kept in the same range. However, if the slope or trend rate is significantly larger than the previous slope or trend rate, it is predicted that future voltage points will deviate significantly from the existing range, and the input offset is moved to the next range accordingly.

[0052] In the third example, the digital controller 208 includes a software algorithm that continuously adjusts the input offset to obtain optimal linearity and resolution for the ADC330. Furthermore, in this example, it may be possible to deploy countless small ranges to detect and adjust the input offset in real time. Adjusting the range classification and resolution enables the acquisition and digitization of a stable and reliable detector signal, and may improve the signal-to-noise ratio. However, it is important to consider various other methods, such as those using nonlinear methods (e.g., ANN, fuzzy), to perform predictive or trend analysis of signal amplitude and signal intensity, and to automatically and adaptively switch signal ranges to obtain the highest quality detector signal while minimizing errors.

[0053] As described above, the method may proceed to step 508 to maintain the same signal range, or to step 810 to switch to a more precise next signal range using one of the illustrated methods. In various embodiments, the range can differ by up to twofold. In various embodiments, the signal is moduloable, and range changes may be limited to the beginning of the modulation cycle to prevent glitches in the output.

[0054] It should be noted that the functions described in relation to the various embodiments described herein may be used in any combination without departing from the spirit and scope of the disclosure. Although different embodiments are illustrated and described in detail, these are illustrative only and should be understood to be subject to various substitutions and modifications without departing from the spirit and scope of the disclosure.

Claims

1. A conductivity detection module for an ion chromatography system, A detection cell configured to receive an eluent flow from an ion chromatography system, comprising a first electrode and a second electrode that are in electrical contact with the eluent flow, A first current branching unit connected to the first cell drive input and the first electrode, which provides the first cell output, Conductivity detection module comprising a second cell drive input and a second current branch connected to the second electrode and providing a second cell output, wherein the first cell drive input and the second cell drive input are of equal magnitude and opposite sign.

2. The conductivity detection module according to claim 1, wherein the detection cell does not have a ground electrode.

3. The conductivity detection module according to claim 1 or 2, wherein the voltage applied to the detection cell is the difference between the first cell drive input and the second cell drive input.

4. The conductivity detection module according to any one of claims 1 to 3, wherein the first cell output and the second cell output correspond to the product of the current flowing through the detection cell and the gain.

5. An ion chromatography system, The conductivity detection module according to any one of claims 1 to 4, A cell drive DAC configured to provide the first cell drive input and the second cell drive input, An ion chromatography system comprising a cell current ADC configured to convert the first cell output and the second cell output into digital outputs.

6. The control unit further comprises a control unit configured to compare the digital output with a signal range. The ion chromatography system according to claim 5, wherein the control unit is configured to generate a cell drive level signal based on the comparison and to provide the cell drive level signal to the cell drive DAC.

7. The control unit further comprises a control unit configured to compare the digital output with a signal range. The ion chromatography system according to claim 5 or 6, wherein the control unit is configured to generate a cell drive level signal based on the comparison and provide the cell drive level signal to the cell drive DAC so as to maintain the digital output of the cell current ADC within the signal range.

8. A signal processing assembly for a conductivity detector in an ion chromatography system, A cell-driven DAC configured to provide a voltage-driven voltage to a detection cell, wherein the voltage amplitude is based on a cell-driven level signal, and the detection cell is configured to receive an eluent flow from the ion chromatography system, A differential cell drive and transimpedance amplifier circuit for amplifying the output of the measurement cell, A cell current ADC configured to convert the output of the signal amplifier into a digital output, A signal processing assembly for a conductivity detector comprising: a control unit configured to compare a digital output with a signal range, wherein the control unit is configured to generate a cell drive level signal based on the comparison and to output the cell drive level signal to a cell drive DAC.

9. The signal processing assembly for a conductivity detector according to claim 8, wherein the control unit adjusts and generates the cell drive level signal so as to maintain the digital output within the signal range.

10. The signal processing assembly for conductivity detector according to claim 8 or 9, wherein the detection cell does not have a ground electrode.

11. The detection cell includes a first electrode and a second electrode that are in electrical contact with the eluent flow. The differential cell drive and transimpedance amplification circuit is, A first current branch unit connected to the first cell drive input from the cell drive DAC and the first electrode, which provides the first cell output, A signal processing assembly for a conductivity detector according to claim 8, 9, or 10, comprising: a second cell drive input from the cell drive DAC and a second current branch connected to the second electrode and providing a second cell output.

12. The signal processing assembly for conductivity detector according to claim 11, wherein the voltage applied to the detection cell is the difference between the first cell drive input and the second cell drive input.

13. The signal processing assembly for a conductivity detector according to claim 11 or 12, wherein the first cell output and the second cell output correspond to the product of the current flowing through the detection cell and the gain.

14. A signal processing assembly for a conductivity detector in an ion chromatography system, A cell-driven DAC configured to provide a voltage-driven voltage to a detection cell, wherein the voltage amplitude is based on a cell-driven level signal, and the detection cell is configured to receive an eluent flow from the ion chromatography system, A differential cell drive and transimpedance amplifier circuit for amplifying the output of the measurement cell, A cell current ADC configured to convert the output of the signal amplifier into a digital output, A signal processing assembly comprising: a control unit including ADC data range scaling logic and filtering logic, wherein the ADC data range scaling logic is operable to adjust the digital output of the cell current ADC taking into account range scaling applied to the cell drive DAC by the cell drive level signal, and the filtering logic is operable to reduce high-frequency noise, and the ADC data range scaling logic operates before the filtering logic.

15. The signal processing assembly according to claim 14, further comprising a control unit, decimator logic operable to reduce the sampling frequency, wherein the decimator logic operates between the ADC data range scaling logic and the filtering logic.

16. The signal processing assembly according to claim 14 or 15, wherein the control unit includes a low-latency channel for comparing the digital output with a signal range, generates the cell drive level signal based on the comparison, and provides the cell drive level signal to the cell drive DAC.

17. The signal processing assembly according to claim 16, wherein the control unit generates the cell drive level signal to maintain the digital output within the signal range.

18. The detection cell comprises a first electrode and a second electrode that are in electrical contact with the eluent flow. The differential cell drive and transimpedance amplification circuit is, A first current branching unit connected to the first cell drive input from the cell drive DAC and the first electrode, which provides a first cell output, A signal processing assembly for a conductivity detector according to any one of claims 14 to 17, comprising: a second cell drive input from the cell drive DAC and a second current branch connected to the second electrode and providing a second cell output.

19. The signal processing assembly for conductivity detector according to claim 18, wherein the voltage applied to the detection cell is the difference between the first cell drive input and the second cell drive input.

20. The signal processing assembly for a conductivity detector according to claim 18 or 19, wherein the first cell output and the second cell output correspond to the product of the current flowing through the detection cell and the gain.

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