Detection signal processing apparatus, detection apparatus and methods of operation thereof

Abstract

A detection signal processing apparatus configured to process detection signals received from a detector for identifying the presence of one or more substances of interest in a sample, the apparatus comprising: a detection signal coupling arranged to receive detection signals from said detector; an amplifier and an integration capacitor, the amplifier having inputs, with at least one input being connected to the detection signal coupling; and ringing circuitry capacitively coupled to at least one of the inputs of the amplifier and being selectively operable to apply a ringing signal to said at least one of the inputs of the amplifier to cause amplifier protection circuitry of the amplifier to reset the integration capacitor.

Description

[0001] Detection Signal Processing Apparatus, Detection Apparatus and Methods of Operation Thereof

[0002] Technical Field

[0003] The present disclosure relates to the field of detection signal processing apparatuses. In particular, the present disclosure relates to detection signal processing apparatuses for processing detection signals received from a detector for identifying the presence of one or more substances of interest in a sample.

[0004] Background

[0005] A detector will typically generate an analogue electrical signal which contains information about the detection performed by that detector. Such analogue electrical signals will be converted into a digital representation thereof, and often this will also involve use of one or more different forms of electrical signal processing circuitry. In some instances, an integrating amplifier will be used. An integrating amplifier can consist of an amplifier and an associated integration capacitor, the integration capacitor typically being connected between an input terminal and an output terminal of the amplifier. The integration capacitor may periodically be reset by discharging it. A method for discharging the integration capacitor is to include a transistor in the circuitry which is connected to provide a second path in parallel to the integration capacitor. Once activated, the transistor will conduct current to provide a low resistance path in parallel to the integration capacitor, thereby to enable the capacitor to discharge.

[0006] The present disclosure is directed to improved arrangements for resetting an integration capacitor.

[0007] Summary

[0008] Aspects of the disclosure are set out in the independent claims and optional features are set out in the dependent claims. Aspects of the disclosure may be provided in conjunction with each other, and features of one aspect may be applied to other aspects.

[0009] In an aspect, there is provided a detection signal processing apparatus configured to process detection signals received from a detector for identifying the presence of one or more substances of interest in a sample, the apparatus comprising: a detection signal coupling arranged to receive detection signals from said detector; an amplifier and an integration capacitor, the amplifier having inputs, with at least one input being connected to the detection signal coupling; and ringing circuitry capacitively coupled to at least one of the inputs of the amplifier and being selectively operable to apply a ringing signal to said capacitive coupling to cause a voltage excursion on at least one of the inputs of the amplifier to cause amplifier protection circuitry of the amplifier to conduct, changing the charge within the capacitive coupling and upon removal of the ringing signal reset the integration capacitor.

[0010] Embodiments may provide an improved arrangement for resetting the integration capacitor. The present inventors have identified that, when the reset involves use of a transistor arranged to provide a low resistance path in parallel to the integration capacitor, the presence of this transistor introduces its own noise into the system (and thus into the resulting measurements obtained using output signals from the detection signal processing apparatus). For instance, controlling the transistor will inject charge into the integration capacitor when switching the transistor from the on state to the off state, and the transistor may have leakage paths that introduce noise and cause the integrator to drift faster than it would without the transistor. Likewise, shorting out the integration capacitor in this manner may lead to the output of the amplifier being at the same voltage as the input, and this may be sub-optimal for total integration time. By providing a detection signal processing apparatus which avoids these additional compromising factors, the output signals will be more accurate and reliable, as they will not have been influenced by such additional noise factors. This increase in accuracy will find particular utility for more sensitive measurement circuits, such as those used in detectors for identifying the presence of a substance of interest in a sample (e.g. in an ion mobility spectrometer).

[0011] Furthermore, embodiments may enable the voltage across the integration capacitor to be set to a selected voltage. Being able to set the voltage across the integration capacitor enables the output of the amplifier to be set to a specific voltage. Being able to set the output to a specific voltage may enable the total charge that can be integrated to be maximised. In turn, this may allow for longer integration times for a given integration capacitor or a smaller integration capacitor may be used for the integrator without compromising on integration times (as compared to other methods for resetting the integrator).

[0012] The amplifier protection circuitry may be configured to direct current away from the relevant input of the amplifier. In particular, the amplifier protection circuitry may be configured to direct current away from either amplifier input in response to a voltage at said input exceeding a threshold value. For this, the amplifier protection circuitry may comprise one or more diodes, each diode operable to divert current flow through said diode and away from an input of the amplifier to which said diode is connected. Current may be diverted from said input of the amplifier to one or more of: (i) a reference voltage connection of the amplifier, such as voltage supply rails, and / or (ii) the other input of the amplifier.

[0013] For example, the amplifier may comprise one or more supply connections (e.g. supply rails, such as high and low voltage supply rails, or connections thereto). The amplifier protection circuitry may be arranged to divert the current flow away to at least one of the supply connections (e.g. to direct current flow to the high voltage rail). For example, in response to a voltage at the input(s) being outside of a threshold voltage range (e.g. above a higher voltage threshold or below a lower voltage threshold), a diode of the amplifier protection circuitry will electrically conduct (e.g. to act to restore the voltage at said input(s) towards a voltage within the threshold voltage range). The amplifier protection circuitry may comprise two diodes at the inverting input. Each diode may be coupled to a voltage supply rail (or a connection thereto) of the amplifier (e.g. with one diode coupled to the high supply rail and the other diode coupled to the low supply rail). Each diode may be arranged in a reverse- biased configuration. A high diode may selectively conduct in response to a voltage at the input(s) exceeding an upper threshold voltage (e.g. a voltage of the high supply rail). A low diode may selectively conduct in response to a voltage at the input(s) being below a lower threshold voltage (e.g. a voltage of the low supply rail). Each of the two inputs of the amplifier (inverting and non-inverting) may have two diodes coupled thereto.

[0014] Additionally, or alternatively, the amplifier protection may also be arranged to divert the current flow away from one of the inputs of the amplifier to the other input of the amplifier. The amplifier protection circuitry may be configured to divert current flow from the first input to the second input and from the second input to the first input. For example, in response to a voltage at the input(s) being outside of a threshold voltage range (e.g. above a higher voltage threshold or below a lower voltage threshold), a diode of the amplifier protection circuitry will electrically conduct (e.g. to act to restore the voltage at said input(s) towards a voltage within the threshold voltage range). The first input may be connected to an anode of one diode and a cathode of another diode, and the second input may be connected to a cathode of said one diode and an anode of said another diode. Each diode may be coupled to the non-inverting input (or a connection thereto) of the amplifier. The diodes may be arranged in a back-to-back configuration such that the first input is coupled to the anode of the first diode and the cathode of the first diode is coupled to the second input and where the first input of the amplifier is coupled to the cathode of the second diode and the anode of the second diode is coupled to the second input of the amplifier. A first diode may selectively conduct in response to a voltage at the input(s) exceeding an upper threshold voltage (e.g. a voltage of the other input connection). A second diode may selectively conduct in response to a voltage at the input(s) being below a lower threshold voltage (e.g. a voltage of the other input connection). The amplifier protection circuitry may be arranged to divert the current flow away from one of the inputs of the amplifier to the other input of the amplifier. The amplifier protection circuitry may be arranged to divert the current flow away from a first input of the amplifier to the second input of the amplifier and from the second input of the amplifier to the first input of the amplifier. The amplifier protection circuitry may be arranged to divert current flow away in response to a voltage associated with said at least one of the inputs exceeding a threshold voltage. The threshold voltage may comprise a voltage associated with the other input.

[0015] The amplifier protection circuitry may be arranged to divert current flow away in response to a voltage associated with said at least one of the inputs exceeding a threshold voltage. Where the amplifier protection circuitry is configured to divert current away to a supply connection, the threshold voltage may be based on a supply connection voltage (e.g. a voltage of the supply rails). For example, the threshold voltage may be the supply connection voltage. Each of the two diodes may be connected to a respective supply connection (e.g. supply rail), and each threshold voltage may be the voltage of the respective supply rail. Where the amplifier protection circuitry is configured to divert current away from one input of the amplifier to the other input, the threshold voltage may be based on a voltage of the other input (e.g. a voltage supplied to the other input).

[0016] In other words, the amplifier protection circuitry is configured to limit a voltage excursion at each amplifier input.

[0017] The amplifier protection circuitry may comprise at least one diode (e.g. two diodes for each input). Each diode may comprise a steering diode (e.g. a protective diode). The amplifier protection circuitry may comprise at least two diodes. The amplifier may comprise the amplifier protection circuitry. The amplifier protection circuitry may be integrated into the amplifier. The amplifier and the amplifier protection circuitry may be provided by a single integrated circuit.

[0018] The apparatus may comprise a voltage source selectively operable to apply a reset pulse into the ringing circuitry to cause the ringing circuitry to provide voltage oscillations at the at least one of the inputs capacitively coupled to the ringing circuitry. The reset pulse may be selected so that some of the coupled voltage oscillations at the amplifier input have a magnitude which exceeds the threshold voltage. The reset pulse may be applied to provide a voltage transient above a threshold level. Applying the reset pulse to provide a voltage transient above the threshold level may comprise applying a selected voltage and then abruptly stopping applying that selected voltage. The voltage transient may comprise a voltage at a magnitude greater than a maximum output voltage for the amplifier. The apparatus may be configured to apply the reset pulse in the event that a saturation condition is detected for the amplifier.

[0019] The apparatus may be configured to control the duration that the voltage source is applied to the ringing circuit and / or the voltage level applied to provide a selected charge that remains in the integration capacitor, e.g. thereby to control the voltage across the integration capacitor and the voltage on the output connection of the amplifier. The applied pulse to the ringing circuit may be an adjustable current source. The apparatus may be configured to adjust the current applied to provide a selected charge that remains in the integration capacitor, e.g. thus controlling the voltage across the integration capacitor and the voltage on the output connection of the amplifier.

[0020] The amplifier may have a first (e.g. non-inverting) input, a second (e.g. inverting) input, and an output. The integration capacitor may be coupled between the second input and the output. The ringing circuitry may be capacitively coupled to the second input of the amplifier. The capacitive coupling may be the integration capacitor, a parasitic capacitance or an additional capacitor. The first input is a non-inverting input, and the second input is an inverting input. The ringing circuitry may be coupled to the inverting input. For example, the ringing circuitry may be capacitively coupled to the inverting input.

[0021] A first plate of the integration capacitor may be coupled to the second input, and a second plate of the integration capacitor may be coupled to the ringing circuitry. The ringing circuitry may be coupled to the output of the amplifier. An inductance and a capacitance of the ringing circuitry may be arranged in parallel between the second plate of the integration capacitor and the output of the amplifier.

[0022] Additionally, or alternatively, the first plate of the integration capacitor may be coupled to the second input of the amplifier and the second plate of the integration capacitor may be coupled to the output of the amplifier. The ringing circuit may be capacitively coupled to the second input of the amplifier by a capacitive coupling. The capacitive coupling may comprise an additional capacitor and / or a parasitic capacitance. The amplifier protection circuitry may comprise two diodes for each of the two inputs of the amplifier. The diodes may be steering diodes. The apparatus may be configured to receive detection signals from an ion mobility spectrometer.

[0023] In an aspect, there is provided a detection apparatus for detecting the presence of a substance of interest in a sample, the apparatus comprising: a detector configured to provide detection signals for the sample indicative of substance detection performed by the detector; and a detection signal processing apparatus for processing the detection signals from the detector. The detection signal processing apparatus comprises: an amplifier and an integration capacitor, the amplifier having inputs, with at least one input being connected to receive the detection signals from the detector; and ringing circuitry capacitively coupled to at least one of the inputs of the amplifier and being selectively operable to apply a ringing signal to said at least one of the inputs of the amplifier to cause amplifier protection circuitry of the amplifier to reset the integration capacitor. The detection signal processing apparatus may comprise any detection signal processing apparatus disclosed herein.

[0024] In an aspect, there is provided a method of operating a detection signal processing apparatus to process detection signals received from a detector for identifying the presence of one or more substances of interest in a sample, wherein the apparatus comprises: (i) a detection signal coupling arranged for receiving detection signals from the detector, (ii) an amplifier and an integration capacitor, the amplifier having inputs, with at least one input being connected to the detection signal coupling, and (iii) ringing circuitry capacitively coupled to at least one of the inputs of the amplifier, wherein the method comprises: capacitively coupling a ringing signal to said at least one of the inputs of the amplifier to cause amplifier protection circuitry of the amplifier to conduct thereby changing the charge within the capacitive coupling capacitance and upon removal (decay) of the ringing signal to reset the integration capacitor.

[0025] The method may comprise receiving a first detection signal from the detector and operating the amplifier and integration capacitor to integrate said detection signal to provide an output signal indicative of the presence of the substance of interest in the sample. The ringing signal may be applied to reset the integration capacitor prior to receiving and integrating a second detection signal from the detector. Applying the ringing signal may comprise applying the ringing signal in the event that a saturation condition is detected for the amplifier.

[0026] In an aspect, there is provided a method of operating a detection apparatus for detecting the presence of a substance of interest in a sample, wherein the apparatus comprises: a detector for providing detection signals for the sample indicative of substance detection performed by the detector, and a detection signal processing apparatus for processing the detection signals from the detector, the detection signal processing apparatus comprising: (i) an amplifier and an integration capacitor, the amplifier having inputs, with at least one input being connected to receive detection signals from the detector, and (ii) ringing circuitry capacitively coupled to at least one of the inputs of the amplifier, wherein the method comprises: applying a ringing signal to said at least one of the inputs of the amplifier to cause amplifier protection circuitry of the amplifier to conduct thereby changing the charge within the capacitive coupling and upon removal of the ringing signal to reset the integration capacitor.

[0027] Aspects of the present disclosure provide one or more computer program products comprising computer program instructions configured to program a voltage source to apply a voltage pulse into ringing circuitry of an apparatus to cause the apparatus to perform any of the methods disclosed herein.

[0028] Figures

[0029] Some examples of the present disclosure will now be described, by way of example only, with reference to the figures, in which:

[0030] Fig. 1a shows a schematic illustration of a detection apparatus.

[0031] Fig. 1b shows a schematic illustration of a detection apparatus.

[0032] Figs. 2a, 2b and 2c each show a schematic illustration of a detection signal processing apparatus.

[0033] Fig. 3 shows a schematic illustration of a detector.

[0034] In the drawings like reference numerals are used to indicate like elements.

[0035] Specific Description

[0036] The present disclosure is directed to systems and methods for resetting an integration capacitor of detection signal processing circuitry used to process detection signals received from a detector. The integration capacitor is connected between one of the inputs of an amplifier and the output of the amplifier. Ringing circuitry is also provided, which is configured to capacitively couple a ringing signal (e.g. large amplitude oscillations in current / voltage) to one of the inputs of the amplifier. Amplifier protection circuitry of the amplifier directs current flow (associated with the ringing signals) away from the input(s) of the amplifier. The amplifier protection circuitry comprises protection diodes which are arranged to direct the current away from the relevant input. The diodes may direct current away to voltage supply rails of the amplifier, to the other amplifier input and / or to another reference voltage. , This directing away of current will act to change the charge within the capacitive coupling and upon removal of the ringing signal change the charge within the integration capacitor.

[0037] Two example detection apparatuses will now be described with reference to Figs. 1a and 1b. The two example apparatuses show different arrangements for both the ringing circuitry and the amplifier protection circuitry. As described in more detail below, the ringing circuitry may be capacitively coupled to an input of the amplifier via either the integration capacitor (as in Fig. 1a) or via a separate capacitive coupling (as in Fig. 1b). Likewise, the amplifier protection circuitry may comprise diodes for steering current towards one or more reference voltage lines, such as the voltage rails of the amplifier (as in Fig. 1a) or the diodes may be for steering current between the two inputs of the amplifier (as in Fig. 1b). Although each of Figs. 1a and 1b shows one specific combination, it will be appreciated that the ringing circuitry of either figure may be used in combination with the amplifier protection circuitry of either figure.

[0038] Reference will first be made to the detection apparatus shown in Fig. 1a.

[0039] The detection apparatus of Fig. 1a includes a detector 280 and a detection signal processing apparatus. The detection signal processing apparatus includes ringing circuitry 100, an amplifier 10 and an integration capacitor 50. The detection signal processing apparatus also includes a detection signal coupling 15.

[0040] The amplifier 10 has two inputs (non-inverting input 20 and an inverting input 30) and an output 40. In the example shown in Fig. 1a, the amplifier 10 includes two supply connections (e.g. each for connection to a respective reference voltage). The supply connections are in the form of voltage supply rails (high supply rail 11 and low supply rail 12). The amplifier 10 includes amplifier protection circuitry. The amplifier protection circuitry is formed of one or more diodes. As shown in Fig. 1a, the amplifier protection circuitry includes two diodes for each of the two inputs 20 and 30 of the amplifier 10. For the non-inverting input 20, there is a non-inverting input high diode 21 and a non-inverting input low diode 22. For the inverting input 30, there is an inverting input high diode 31 and an inverting input low diode 32. It will be appreciated that the amplifier 10 may include additional components to those shown in Fig. 1a, but these additional components are not illustrated. Instead, Fig. 1a just shows example components for implementing the amplifier protection functionality of the present disclosure. Also, as described below in relation to Fig. 2a, the integration capacitor 50 may form a part of the ringing circuitry 100, but the two are shown as separate components in Fig. 1a just as an example to illustrate their respective arrangement and functionality.

[0041] The detector 280 is coupled to the amplifier 10 via the detection signal coupling 15. A first plate of the integration capacitor 50 is coupled to the inverting input 30 of the amplifier 10. The detector 280 is also coupled to the inverting input 30 of the amplifier. In the example shown in Fig. 1a, a second plate of the integration capacitor 50 is coupled to the ringing circuitry 100. The ringing circuitry 100 is also coupled to the output 40 of the amplifier 10. In other words, the ringing circuitry 100 is connected between the integration capacitor 50 and the output 40 of the amplifier 10 (e.g. with the combination of the integration capacitor 50 and the ringing circuitry 100 connected between one input, namely the inverting input 30, and one output 40 of the amplifier). The non-inverting input 20 of the amplifier 10 may be coupled to a reference voltage, such as a ground.

[0042] As shown in Fig. 1a, the non-inverting input 20 is coupled to the high supply rail 11 via the non-inverting input high diode 21. The anode of the non-inverting input high diode 21 is coupled to the non-inverting input 20, and the cathode of the non-inverting input high diode 21 is coupled to the high supply rail 11. The non-inverting input 20 is coupled to the low supply rail 12 via the non-inverting input low diode 22. The cathode of the non-inverting input low diode 22 is coupled to the non-inverting input 20, and the anode of the non-inverting input low diode 22 is coupled to the low supply rail 12.

[0043] The inverting input 30 is coupled to the high supply rail 11 via the inverting input high diode 31. The anode of the inverting input high diode 31 is coupled to the inverting input 30, and the cathode of the inverting input high diode 31 is coupled to the high supply rail 11. The inverting input 30 is coupled to the low supply rail 12 via the inverting input low diode 32. The cathode of the inverting input low diode 32 is coupled to the inverting input 30, and the anode of the inverting input low diode 32 is coupled to the low supply rail 12.

[0044] The first plate of the integration capacitor 50 is coupled to the inverting input 30 (and thus may be connected to the high and low supply rails via the two inverting input diodes 31 , 32) and the second plate of the integration capacitor 50 is coupled to the ringing circuitry 100

[0045] The detector 280 is configured to output a detection signal indicative of detection performed by the detector 280. The detector 280 is arranged for identifying the presence of one or more substances of interest in a sample. For example, the detector 280 may comprise a spectrometer, such as an ion mobility spectrometer ( MS’). An output signal from the detector 280 may be in the form of an electrical signal, such as a current or voltage pulse. The electrical signal may provide an indication of a detected substance. For example, where the detector 280 comprises an IMS, each output signal from the detector 280 may be indicate of incident ions on a detector plate, e.g. where the ions may be identified based on the time it took them to travel to that detector plate (and the number of incident ions at each time may be determined based on an amplitude of that electrical signal).

[0046] The detection signal coupling 15 is arranged to couple the detector 280 to the amplifier 10. The detection signal coupling 15 may comprise a portion of electrical conductor, e.g. which is arranged to transmit an electrical signal from the detector 280 to the inverting input 30 of the amplifier 10 and integration capacitor.

[0047] The ringing circuitry 100 is configured to generate ringing signals. Although not shown in Fig. 1a, the ringing circuitry 100 may be coupled to a voltage source. The voltage source may be arranged to generate one or more reset pulses (e.g. voltage pulses). The ringing circuitry 100 also includes some capacitance and some inductance (e.g. a capacitor and an inductor). At least some of the capacitance may be provided by the integration capacitor 50, or it may be provided by another source of capacitance (e.g. an additional capacitor or a parasitic capacitance). The inductance and capacitance may be connected in parallel with each other. The voltage source may be configured to apply a reset pulse (a voltage pulse) into the ringing circuitry 100 to cause voltage oscillations to occur, i.e. to provide a ringing signal. The ringing circuitry 100 is capacitively coupled to the inverting input 30 of the amplifier 10 (via the integration capacitor 50 in Fig. 1a) so as to provide said ringing signals to the inverting input 30.

[0048] The amplifier protection circuitry may form part of the amplifier 10, i.e. the protection circuitry may be integrated into the amplifier 10. For example, the amplifier 10 (including the amplifier protection circuitry) may be provided by a single integrated circuit.

[0049] Each of the diodes of the amplifier protection circuitry is arranged to provide a steering diode. In normal use (e.g. when the voltage at each input is between the voltage of the low and high supply rails), each diode may be arranged in a reverse-biased configuration (e.g. with its cathode at a higher voltage than its anode). In other words, in normal use, each diode is arranged to inhibit electrical conduction between the input and the relevant supply rail. In response to a voltage at the input exceeding a threshold value (positive or negative), an electrical conduction path may be defined through that diode (e.g. between the input and the relevant supply rail). As such, when a voltage at the input exceeds the threshold value, the diode will become electrically conductive thereby to enable current flow therethrough to restore the voltage at said input to a value between that of the two supply rails (i.e. to a normal use value).

[0050] For example, in the event that a voltage at the input exceeds the high supply rail voltage, the relevant high diode may be configured to permit current flow therethrough. As such, current may flow from that input through the diode to the high supply rail 11, and thereby to reduce an input voltage. Likewise, in the event that a voltage at the input is less than the low supply rail voltage, the relevant low diode may be configured to permit current flow therethrough.

[0051] In other words, the amplifier protection circuitry may be configured to selectively provide one or more electrical conduction paths for diverting current flow in response to the voltage at said input being outside a threshold voltage range. The threshold voltage range may be the range of voltages between the voltage of the low supply rail 12 and the voltage of the high supply rail 11. The amplifier protection circuitry may be configured to selectively provide such electrical conduction path(s) to permit current flow so as to restore the voltage at the input to a value within the threshold voltage range. For example, the amplifier protection circuitry may be configured to divert current flow away from the input and towards the high supply rail 11 in response to the voltage at said input exceeding a threshold value (i.e. exceeding the voltage of the high supply rail 11).

[0052] The ringing circuitry 100 is configured to capacitively couple a ringing signal to the amplifier 10. In particular, the ringing circuitry 100 may be configured to capacitively couple a ringing signal to the inverting input 30 of the amplifier 10. The ringing signal is arranged to activate the amplifier protection circuitry, e.g. to provide conduction through the relevant diode(s) of the amplifier 10. The ringing signal may be configured to activate the steering diodes of the amplifier 10 to direct current flow as set out above (e.g. to act to restore the voltage at the inverting input 30 to within the threshold range). The ringing signal may have voltage oscillations such that the resulting voltages are outside the threshold voltage range. That is, the maximum / minimum voltages of the voltage oscillations may be greater / lower than the voltages of the high / low supply rails (respectively). To generate the ringing signal, the voltage source may be configured to apply a selected voltage to the ringing circuitry 100 for a first period of time before abruptly stopping the application of that selected voltage to the ringing circuitry 100. This voltage applied to the reset circuitry may be referred to as a ‘reset pulse’. The reset pulse may comprise a voltage pulse at a voltage having a greater magnitude than a maximum output voltage for the amplifier 10. The application of this reset pulse to the ringing circuitry 100 is configured to cause the ringing circuitry 100 to provide sufficient voltage oscillations to activate the diodes of the amplifier protection circuitry. In other words, the voltage source is configured to inject a sufficient amount of charge into the apparatus (e.g. to the inverting input30) to cause current to flow through the inverting input diodes 31 , 32.

[0053] As set out above, the detection signal processing apparatus is configured to perform a reset. For this, the charge stored by the integration capacitor 50 may be reset to a selected value. The detection apparatus may be configured to selectively perform a reset procedure. This reset may be performed in response to certain conditions. As will be appreciated in the context of the present disclosure, each time a detection signal from the detector 280 is processed by the amplifier 10, the capacitor may be further charged up, until a saturation condition for the amplifier 10 occurs. At which point, the output from the amplifier 10 for any further detection signals from the detector 280 may be of little to no use for detecting the presence of a substance of interest. The detection apparatus of the present disclosure may be configured to detect an indication of saturation condition. For example, an indication of saturation (or closeness to saturation) may be obtained from the apparatus, and / or an indication of saturation may be inferred based on a number of measurements (e.g. amplification integrations) performed since a previous reset. The apparatus may be configured to perform a reset procedure in the event that a saturation condition is detected. For example, in the event that it is determined that the apparatus is at, or close to, a saturation condition, the reset procedure may be performed. Alternatively, a reset procedure may be performed after each time a measurement is obtained using the integration amplifier 10.

[0054] The apparatus may be configured to control the duration that a voltage source is applied to the ringing circuit and / or the voltage level applied may be controlled to control the charge that remains in the integration capacitor after the reset process is finished. That is, the apparatus may be configured to apply a voltage pulse for a selected duration and / or at a selected voltage level thereby to provide a selected amount of charge remaining on the integration capacitor once the reset is complete (and therefore voltage on the output connection of the amplifier). Additionally, or alternatively, the applied pulse to the ringing circuit may be an adjustable current source. Adjustment of the current applied may be controlled to affect the charge that remains in the integration capacitor. In other words, the current applied may be controlled to select the voltage across the integration capacitor and therefore the voltage on the output connection of the amplifier.

[0055] In operation, the detection signal processing apparatus may receive a detection signal from the detector 280 (via the detection signal coupling 15). The detection signal is in the form of a current signal, and that signal is provided to the inverting input 30 of the amplifier 10 for integration thereof. The amplifier 10 may output a voltage which is proportional to the integral of the input current (i.e. which is indicative of the detection signal). This output signal may be converted into a digital signal to be used for identifying the presence of one or more substances of interest in the sample being analysed by the detector 280. This process may occur once, or multiple times, before it is determined that a reset procedure is to be performed for the amplifier 10.

[0056] Once it is determined that a reset procedure is to be performed, the voltage source is used to generate a voltage pulse which is applied to the ringing circuitry 100 for a first time period before abruptly stopping that application of the voltage pulse. In turn, this causes the ringing circuitry 100 to start ‘ringing’ (e.g. oscillating). This ringing signal from the ringing circuit is capacitively coupled to the inverting input 30 of the amplifier 10. That is, the ringing causes large voltage excursions at the inverting input 30 of the amplifier 10.

[0057] These voltage excursions will act to pull the inverting input 30 of the amplifier 10 to voltages which are sufficiently above the voltage of the high supply rail 11 and / or to voltages which are sufficiently below the voltage of the low supply rail 12. In turn, this will force one or more diodes of the amplifier protection circuitry to conduct, thereby to draw current therethrough (and to act to restore the voltage at the inverting input 30 back towards being within the threshold voltage range, where the remaining voltage may be selected by controlling the reset pulse accordingly). As a result of the ringing of the ringing circuitry 100, and the corresponding large voltage excursions at the inverting input 30, current will be drawn through the diodes of the amplifier protection circuitry. A magnitude of the oscillations in voltage at the inverting input 30 will decrease with time, as will a magnitude in oscillation in voltage across the integration capacitor 50. For the output voltage, this may oscillate for a while between the voltages of the two supply rails (without any substantial decrease in the amplitude of the voltage oscillations), before this oscillation amplitude then decreases. After this oscillation period has finished, the voltage at the two inputs 20, 30, the output 40 and across the integration capacitor 50 will have been restored to a selected value. In other words, this ringing process will reset the voltage across the integration capacitor 50. At which point, the detection signal processing apparatus is then prepared for processing further detection signals without being near to a saturation condition, and with an output voltage for the amplifier 10 being set to a selected value.

[0058] As described herein, the ringing circuitry 100 may have some form of capacitance and inductance for generating ringing signals in response to a voltage applied into the ringing circuitry 100 by a voltage source.

[0059] The capacitive coupling between the ringing circuit 100 and the inverting input 30 of the amplifier 10 could be any suitable form of capacitance that may be coupled to the inverting input 30 of the amplifier 10 (and which is arranged to enable enough charge to be provided to the inverting input 30 to cause current to flow through the diodes of the amplifier protection circuitry). For example, the ringing circuitry 100 may be capacitively coupled to the inverting input 30 via the integration capacitor 50, as shown in Fig. 1a. Reference will now be made to Fig. 1b, in which ringing circuitry is capacitively coupled to the inverting input 30 via another capacitance.

[0060] As with Fig. 1a, Fig. 1b shows a detection apparatus including a detector 280 and a detection signal processing apparatus. The detection signal processing apparatus includes ringing circuitry 100, an amplifier 10 and an integration capacitor 50. The detection signal processing apparatus also includes a detection signal coupling 15. The amplifier 10 has two inputs (non-inverting input 20 and an inverting input 30) and an output 40. The amplifier 10 includes amplifier protection circuitry. The amplifier protection circuitry is formed of one or more diodes, which in the example of Fig. 1b is two diodes 61 , 62.

[0061] The apparatus of Fig. 1b differs from that of Fig. 1a in two ways. Firstly, the connection of the ringing circuitry 100 is different. Secondly, the amplifier protection circuitry is different.

[0062] For the connection of the ringing circuitry 100, the apparatus of Fig. 1b includes an additional capacitive coupling 51. The capacitive coupling 51 is separate to the integration capacitor 50. The capacitive coupling 51 may comprise a separate capacitor (e.g. a standalone element) or it may be in the form of a parasitic coupling.

[0063] As with Fig. 1a, the detector 280 is coupled to the amplifier 10 via the detection signal coupling 15. The detector 280 and a first plate of the integration capacitor 50 are coupled to the inverting input 30 of the amplifier 10. The second plate of the integration capacitor 50 is coupled to the output 40 of the amplifier 10. In other words, the integration capacitor 50 is connected across the amplifier 10 (e.g. between the inverting input 30 and one output 40 thereof). Unlike in Fig. 1a, the ringing circuitry 100 is not connected between the second plate of the integration capacitor 50 and the output 40. Instead, the ringing circuitry 100 is coupled to the inverting input 30 of the amplifier via the capacitive coupling 51. For instance, one plate (e.g. a first plate) of the capacitive coupling 51 may be coupled to the inverting input 30 (as with the detector 280 and the first plate of the integration capacitor 50). The other plate (e.g. a second plate) of the capacitive coupling 51 may be coupled to the ringing circuitry 100.

[0064] As with Fig. 1a, in Fig. 1b, the non-inverting input 20 of the amplifier 10 may be coupled to a reference voltage, such as a ground. The capacitive coupling 51 may be a discrete component or take the form of a parasitic capacitance formed by conductive couplings separated by an insulator.

[0065] In other words, the apparatus is arranged for the ringing circuitry 100 to apply a ringing signal to the inverting input 30 of the amplifier 10 via capacitive coupling 51.

[0066] As to the amplifier protection circuitry shown in Fig. 1b, this comprises the two diodes 61 , 62. The two diodes 61, 62 are arranged in a back-to-back configuration across the two inputs 20, 30. That is, a first of the diodes 61 , 62 is connected one way between the two inputs 20, 30, and the other of the diodes 61, 62 is connected the other way. As shown in Fig. 1b, the non-inverting input 20 is coupled to the anode of diode 61 and the cathode of diode 62, and the inverting input 30 is coupled to the cathode of diode 61 and the anode of diode 62.

[0067] In other words, the amplifier protection circuitry (diodes 61 , 62) is configured to provide a conduction path between the two inputs 20, 30 of the amplifier 10 in the event that the voltage at either 20 / 30 input exceeds a threshold value. That is, the amplifier protection circuitry may be configured to selectively connect one input to the other input for diverting current flow away from said input in the event that the voltage exceeds the threshold value. In this sense, the amplifier protection circuitry is configured for connecting one input to the other for re-directing current flow away from said input, rather than for directing current towards a reference voltage line, such as a high or low voltage rail, as shown in Fig. 1a.

[0068] The apparatus of Fig. 1b may otherwise function and operate in the same manner as that described above for Fig. 1a. That is, the ringing circuitry 100 may be operated for resetting the amplifier, with the ringing circuitry 100 being connected to the inverting input 30 via capacitive coupling 51. And, the amplifier protection circuitry may implement this reset by directing current flow between the two inputs 20, 30 of the amplifier 10.

[0069] Different example arrangements for detection signal processing apparatuses (and in particular for different arrangements for the ringing circuitry 100) will now be described with reference to Figs. 2a to 2c.

[0070] Each of Figs. 2a to 2c shows a detection signal processing apparatus. As with Fig. 1, each apparatus includes a detection signal coupling 15, an amplifier 10, an integration capacitor 50 and ringing circuitry 100. Each amplifier 10 has a non-inverting input 20, an inverting input 30, an output 40, and high and low supply rails 11 , 12. Although not shown, each amplifier 10 may include amplifier protection circuitry of the type described above in relation to Fig. 1a and / or Fig. 1b. Each apparatus also includes a voltage source 110.

[0071] For the apparatus of Fig. 2a, the ringing circuitry 100 includes a parallel RLC circuit formed of inductor ‘L2’, resistor ‘R2’ and capacitor ‘C4’. The ringing circuitry 100 is coupled between the second plate of the integration capacitor 50 and the output 40 of the amplifier 10. Each of the resistor, the inductor and the capacitor of the ringing circuitry 100 is connected between the second plate of the capacitor and the output 40 of the amplifier 10 (with the three connections arranged in parallel). The first plate of the integration capacitor 50 is coupled to the inverting input 30 of the amplifier 10. The second plate of the integration capacitor 50 and the ringing circuitry 100 are both coupled to the voltage source 110.

[0072] The voltage source 110 of Fig. 2a includes two transistors ‘Q2’ and ‘Q3’ and two diodes ‘D1’ and ‘D3’. The control terminal of each transistor is coupled to a source configured to apply control signals thereto. In Fig. 2a, ‘Control T is a control signal to be applied to the control (e.g. base T) terminal of a first of the two transistors, and ‘Control 2’ is a control signal to be applied to the control (e.g. base T) terminal of a second of the two transistors.

[0073] The first transistor is coupled to the ringing circuitry 100 and second plate of the integration capacitor 50 via a first of the two diodes. The anode of the first diode is connected to the first transistor (e.g. to its collector terminal ‘3’) and the cathode of the first diode is connected to the connection to the ringing circuitry 100 and the second plate of the integration capacitor 50. The other terminal (e.g. the emitter terminal ‘2’) of the first transistor is coupled to a voltage source ‘+V’. The second transistor is coupled to the ringing circuitry 100 and second plate of the integration capacitor 50 via a second of the two diodes. The cathode of the second diode is connected to the second transistor (e.g. to its collector terminal ‘3’) and the anode of the second diode is connected to the connection to the ringing circuitry 100 and the second plate of the integration capacitor 50. The other terminal (e.g. the emitter terminal ‘2’) of the second transistor is coupled to a reference voltage, e.g. a ground ‘-V’.

[0074] The inverting input 30 of the amplifier 10 is coupled to the detection signal coupling 15 (and also the first plate of the integration capacitor 50 as mentioned above). The non-inverting input 20 is connected to a reference voltage ‘REF’. The output 40 of the amplifier 10 may be coupled to a differentiator. As mentioned above, the output 40 is also coupled to the ringing circuitry 100 (each of C4, R2, L2), which is coupled to the second plate of the integration capacitor 50 and the voltage source 110.

[0075] The high supply rail 11 of the amplifier 10 is coupled to a reference voltage ‘+V’. The low supply rail 12 of the amplifier 10 is coupled to a reference voltage ‘-V’.

[0076] The functionality of the apparatus shown in Fig. 2a is much the same as that described above in relation to Fig. 1a. That is, the voltage source 110 is configured to introduce enough charge into the system (i.e. to the ringing circuitry 100 and the second plate of the integration capacitor 50) to cause conduction in the protection diode(s) of the inverting input 30. For this, the apparatus is configured to apply a control signal to the control terminal of the first transistor, thereby to connect the reference voltage to the ringing circuitry 100 and integration capacitor 50 (via the first diode). As such, the voltage source 110 is configured to inject charge into the ringing circuitry 100 / integration capacitor 50 of the apparatus. The apparatus is configured to abruptly disconnect the reference voltage from the ringing circuitry 100 / integration capacitor 50 by stopping the application of the control signal to the control terminal of the first transistor. As will be appreciated, the first diode is arranged to provide a one-way bias for current flow from the reference voltage to the ringing circuitry 100 / integration capacitor 50. A control signal may be applied to the control terminal of the second transistor to enable current to flow therethrough (towards the ground) to introduce charge into the system. The use of control 1 or control 2 may be selected in dependence upon the voltage present on the output connection 40 of amplifier 10.

[0077] As will be appreciated, in response to the voltage source 110 injecting this charge (i.e. the ‘reset pulse’) into the ringing circuitry 100, the ringing circuitry 100 will ring. That is, oscillations in voltage will occur due to the RLC circuit in the ringing circuitry 100. These oscillations will also be apparent across the integration capacitor 50, and at the inverting input 30 of the amplifier 10. As such, the ringing circuitry 100 will cause (large) oscillations in voltage to occur at the inverting input 30. These oscillations will include voltages outside the threshold voltage range (that between the voltage of the low supply rail 12 and the voltage of the high supply rail 11 for the arrangement of Fig. 1a or for the conducting voltages associated with diodes 61, 62 shown in Fig. 1b), thereby causing the steering protection diodes of the amplifier protection circuitry at the inverting input 30 to conduct current therethrough (and thus act to dissipate charge to restore the voltage at the inverting input 30 towards a value within the threshold range). This current may flow from the input to the relevant supply rails (as in Fig. 1a) or to the other input (as in Fig. 1b). As will be appreciated, these oscillations will continue for a time period while they decrease in amplitude, until the oscillations stop. At which point, the integration capacitor 50 will have been reset, and the voltage at the inputs and output of the amplifier 10 have been reset to respective selected values.

[0078] The apparatus of Fig. 2b is similar to that of Fig. 2a. In Fig. 2b, one or more parasitic capacitances may be utilised to provide relevant capacitance(s) for the apparatus. A parasitic capacitance (e.g. capacitive coupling 51) may be coupled to the amplifier’s inverting input 30 for initialising amplifier 10 (e.g. to facilitate a reset procedure of the type described above). As will be appreciated, the particular source of this parasitic capacitance need not be considered limiting - any suitable form of parasitic capacitance could be used. For example, where the detector 280 is an IMS, a parasitic capacitance may be provided from a screen grid to a Faraday plate capacitance, and / or any screening conductor(s) or any guard conductor(s) that are in close proximity to the amplifier’s input.

[0079] In Fig. 2b, the ringing circuitry 100 is again formed of a parallel RLC circuit (capacitance ‘C3’, resistance ‘R1’ and inductance ‘L1’). A parasitic capacitance 51 is coupled to the inverting input 30 of the amplifier 10 and also to the ringing circuitry 100 and the voltage source 110. The ringing circuitry 100 is coupled between this parasitic capacitance 51 and a reference voltage (e.g. a ground ‘-V’), and the ringing circuitry 100 is also coupled to the voltage source 110. For simplicity, reference will be made to first and second ‘plates’ of the parasitic capacitance, but it will be appreciated that this parasitic capacitance may not take the same structure as a standalone capacitor. The first plate of the parasitic capacitance 51 is coupled to the inverting input 30 and the second plate is coupled to both the ringing circuitry 100 and the voltage source 110.

[0080] The voltage source 110 of Fig. 2b includes a transistor ‘Q1’ and a diode ‘D2’. The control terminal (base ‘1’) of the transistor is coupled to a source configured to apply a control signal thereto (‘Control’). The transistor is coupled to the ringing circuitry 100 and second plate of the parasitic capacitance 51 via the diode. The anode of the diode is connected to the transistor (e.g. to its collector terminal ‘3’) and the cathode of the diode is connected to the connection to the ringing circuitry 100 and the second plate of the parasitic capacitance 51. The other terminal (e.g. the emitter terminal ‘2’) of the transistor is coupled to a voltage reference ‘+3V3’. The diode is arranged to provide a one-way conduction path from the transistor (and voltage reference) to the parasitic capacitance 51 / ringing circuitry 100.

[0081] The inverting input 30 of the amplifier 10 is coupled to the detection signal coupling 15 and the first plate of the integration capacitor 50 (and also the first plate of the parasitic capacitance 51 , as mentioned above). The non-inverting input 20 is connected to a reference voltage ‘REF’. The output 40 of the amplifier 10 may be coupled to a differentiator. The high supply rail 11 of the amplifier 10 is coupled to a high reference voltage ‘+V’, and the low supply rail 12 of the amplifier 10 is coupled to a low reference voltage ‘-V’.

[0082] Again, the functionality of the apparatus shown in Fig. 2b is very similar to that of Fig. 2a and Figs. 1a and 1b. That is, the apparatus is configured to apply a control signal to the control terminal of the transistor to permit the reference voltage to inject charge through the transistor and diode and into the ringing circuitry 100 / parasitic capacitance 51 of the apparatus. The apparatus is configured for this to introduce enough charge into the system (i.e. into the ringing circuitry 100 and the second plate of the parasitic capacitance 51) to cause conduction in the protection diodes of the inverting input 30, as described above, for resetting the apparatus.

[0083] The apparatus of Fig. 2c is very similar to that of Fig. 2b, and so the arrangement and functionality of the common components for this apparatus will not be described again. The main difference for Fig. 2c is that instead of a parasitic capacitance 51 (as in Fig. 2b), a separate capacitor 52 is provided. A first plate of this capacitor 52 is coupled to the inverting input 30 of the amplifier 10, and a second plate is coupled to the ringing circuitry 100 and the voltage source 110. As will be appreciated, this apparatus may function and operate in the same manner as Fig. 2b (just with the capacitance coupled to the inverting input 30 being in the form of a separate capacitor, rather than a parasitic capacitance).

[0084] As described herein, detection signal processing apparatuses of the present disclosure are configured to process detection signals from a detector 280 for identifying the presence of one or more substances of interest in a sample. As will be appreciated in the context of the present disclosure, the detector 280 may be provided by a number of different forms of detector. Examples include any suitable spectrometer, such as a mass spectrometer or an IMS (to name a few). For example, as will be appreciated, apparatuses of the present disclosure may find utility for any detector having an output in the form of a current signal to be processed. One example where an apparatus of the present disclosure finds particular utility is for ion mobility spectrometry, as this technology may require very accurate and precise measurements, and the present disclosure may provide greater reliability and consistency for providing accurate and precise measurements. Reference will now be made to Fig. 3 which shows one example of such a detector.

[0085] Fig. 3 is an illustration of a part section through a detector 280 in the form of an ion mobility spectrometer (‘IMS’) 280.

[0086] The ion mobility spectrometer 280 illustrated in Fig. 3 includes an ioniser 288 that is separated from a drift chamber 292 by a gate 282. The gate 282 can control passage of ions from the ioniser 288 into the drift chamber 292. As illustrated, the IMS 280 includes an inlet 281 for enabling material to be introduced from the sample of interest to the ioniser 288 (e.g. via the inlet passage opening).

[0087] In the example illustrated in Fig. 3, the drift chamber 292 lies between the ioniser 288 and an ion detector 287, so that ions can reach the ion detector 287 by traversing the drift chamber 292. The drift chamber 292 may comprise a series of drift electrodes 283, 284 for applying a voltage profile along the drift chamber 292 to move ions from the ioniser 288 along the drift chamber 292 toward the ion detector 287.

[0088] The IMS 280 may be configured to provide a flow of drift gas in a direction generally opposite an ion's path of travel to the ion detector 287. For example, the drift gas can flow from adjacent the ion detector 287 toward the gate 282. As illustrated, a drift gas inlet 289 and drift gas outlet 290 can be used to pass drift gas through the drift chamber. Example drift gases include, but are not limited to, nitrogen, helium, air, air that is re-circulated (e.g., air that is cleaned and / or dried) and so forth.

[0089] The ion detector 287 may be coupled to provide a signal to a detection controller 294. The ion detector 287 may be configured to provide detection signals of the type described herein. The controller 294 may include a signal processing apparatus of the type disclosed herein for processing such detection signals. For example, a property of the electrical signal output from the ion detector 287 can be used by the controller 294 to infer that ions have reached the ion detector 287, and a characteristic of the ions can be determined based on the time for ions to pass from the gate 282 along the drift chamber 292 to the ion detector 287. Examples of an ion detector 287 are configured to provide a signal indicating that ions have arrived at the ion detector 287. For example, the ion detector 287 may comprise a conductive electrode (such as a Faraday plate).

[0090] Electrodes 283, 284 may be arranged to guide ions toward the ion detector 287, for example the drift electrodes 283, 284 may comprise rings which may be arranged around the drift chamber 292 to focus ions onto the ion detector 287. Although the example of Fig. 3 includes only two drift electrodes 283, 284, in some examples a plurality of electrodes may be used, or a single electrode may be used in combination with the ion detector 287 to apply an electric field to guide ions toward the ion detector 287.

[0091] The spectrometer 280 is shown comprising ion modifier electrodes 285, 286 arranged in the drift chamber, although it is to be appreciated in the context of this disclosure that these may not be included.

[0092] As shown in Fig. 3 a voltage provider 293 is coupled to be controlled by the controller 294. The voltage provider 293 may also be coupled to provide voltages to the ioniser 288 to enable material from a sample to be ionised. In an embodiment the voltage provider 293 is coupled to the gate electrode 282 to control the passage of ions from the ionisation chamber into the drift chamber 292. The voltage provider 293 can be coupled to the drift electrodes 283, 284 for providing a voltage profile for moving ions from the ioniser 288 toward the ion detector 287.

[0093] As noted above, the drift electrodes 283, 284 may provide a voltage profile that moves ions along the drift chamber so that the ions travel from the ioniser toward the ion detector 287. As illustrated in Fig. 3, the first ion modifier electrode 285 and the second ion modifier electrode 286 can be spaced apart in the direction of travel of the ions.

[0094] The spectrometer and the voltage provider may be contained in a common housing. In spectrometry, ion counts may be measured by peaks on a spectrum, and the height of a peak may be an indicator of the number of ions reaching the ion detector 287 at a particular time. Ions which are produced by ions which are produced by reactions of the neutral molecules of the substance of interest may be termed “daughter ions”, and ions from which daughter ions are produced may be termed “parent ions”.

[0095] As noted above, other types of detector may be used. For example, a mass spectrometer may be used such as a time of flight mass-spectrometer. In such spectrometers ions mass to charge ratio may be inferred from their time of flight through a vacuum. In other types of mass spectrometer, ions maybe separated in other ways based on their mass to charge ratios, for example by deflection under electric or magnetic fields.

[0096] It will be appreciated that examples described herein and as shown in the figures are not intended to be limiting. These examples are intended to illustrate examples for implementing the technology. For example, apparatuses of the present disclosure include amplifier protection circuitry configured for resetting the integration capacitor 50. In examples described herein, this circuitry is formed of a plurality of steering diodes, with two diodes coupled to each of the two inputs of the amplifier 10. However, it will be appreciated that this arrangement need not be considered limiting. For example, fewer diodes could be provided. For instance, one or two diodes may be provided at the inverting input 30, but not elsewhere. Similarly, in examples described herein, the amplifier 10 and the amplifier protection circuitry are provided by a single component (e.g. a single integrated circuit). However, this need not be the case. For example, one or more diodes of the amplifier protection circuitry may be provided by separate components to the amplifier 10.

[0097] It will be appreciated from the discussion above that the examples shown in the figures are merely exemplary, and include features which may be generalised, removed or replaced as described herein and as set out in the claims. With reference to the drawings in general, it will be appreciated that schematic functional block diagrams are used to indicate functionality of systems and apparatus described herein. In addition, the processing functionality may also be provided by devices which are supported by an electronic device. It will be appreciated however that the functionality need not be divided in this way, and should not be taken to imply any particular structure of hardware other than that described and claimed below. The function of one or more of the elements shown in the drawings may be further subdivided, and / or distributed throughout apparatus of the disclosure. In some examples the function of one or more elements shown in the drawings may be integrated into a single functional unit.

[0098] As will be appreciated by the skilled reader in the context of the present disclosure, each of the examples described herein may be implemented in a variety of different ways. Any feature of any aspects of the disclosure may be combined with any of the other aspects of the disclosure. For example, method aspects may be combined with apparatus aspects, and features described with reference to the operation of particular elements of apparatus may be provided in methods which do not use those particular types of apparatus. In addition, each of the features of each of the examples is intended to be separable from the features which it is described in combination with, unless it is expressly stated that some other feature is essential to its operation. Each of these separable features may of course be combined with any of the other features of the examples in which it is described, or with any of the other features or combination of features of any of the other examples described herein. Furthermore, equivalents and modifications not described above may also be employed without departing from the present disclosure.

[0099] Certain features of the methods described herein may be implemented in hardware, and one or more functions of the apparatus may be implemented in method steps. It will also be appreciated in the context of the present disclosure that the methods described herein need not be performed in the order in which they are described, nor necessarily in the order in which they are depicted in the drawings. Accordingly, aspects of the disclosure which are described with reference to products or apparatus are also intended to be implemented as methods and vice versa. The methods described herein may be implemented in computer programs, or in hardware or in any combination thereof. Computer programs include software, middleware, firmware, and any combination thereof. Such programs may be provided as signals or network messages and may be recorded on computer readable media such as tangible computer readable media which may store the computer programs in non-transitory form. Hardware includes computers, handheld devices, programmable processors, general purpose processors, application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), and arrays of logic gates.

[0100] Other examples and variations of the disclosure will be apparent to the skilled addressee in the context of the present disclosure.

Claims

Claims1. A detection signal processing apparatus configured to process detection signals received from a detector for identifying the presence of one or more substances of interest in a sample, the apparatus comprising: a detection signal coupling arranged to receive detection signals from said detector; an amplifier and an integration capacitor, the amplifier having inputs, with at least one input being connected to the detection signal coupling; and ringing circuitry capacitively coupled to at least one of the inputs of the amplifier and being selectively operable to apply a ringing signal to said at least one of the inputs of the amplifier to cause amplifier protection circuitry of the amplifier to reset the integration capacitor.

2. The detection signal processing apparatus of claim 1, wherein the amplifier protection circuitry is arranged to divert current flow away from: (i) the at least one of the inputs capacitively coupled to the ringing circuitry, and / or (ii) the integration capacitor.

3. The detection signal processing apparatus of claim 2, wherein the amplifier comprises one or more supply connections, and wherein the amplifier protection circuitry is arranged to divert the current flow away to at least one of the supply connections.

4. The detection signal processing apparatus of claim 2 or 3, wherein the amplifier protection circuitry is arranged to divert current flow away in response to a voltage associated with said at least one of the inputs exceeding a threshold voltage.

5. The detection signal processing apparatus of claim 4, as dependent on claim 3, wherein the threshold voltage is based on a supply connection voltage.

6. The detection signal processing apparatus of any preceding claim, wherein the amplifier protection circuitry comprises at least one diode, optionally wherein the diode is a steering diode.

7. The detection signal processing apparatus of claim 6, wherein the amplifier protection circuitry comprises at least two diodes, optionally wherein each diode is a steering diode.

8. The detection signal processing apparatus of any preceding claim, wherein theamplifier comprises the amplifier protection circuitry, optionally wherein the amplifier protection circuitry is integrated into the amplifier and / or the amplifier and the amplifier protection circuitry are provided by a single integrated circuit.

9. The detection signal processing apparatus of any preceding claim, wherein the amplifier protection circuitry is arranged to divert the current flow away from one of the inputs of the amplifier to the other input of the amplifier.

10. The detection signal processing apparatus of claim 9, wherein the amplifier protection circuitry is arranged to divert the current flow away from a first input of the amplifier to the second input of the amplifier and from the second input of the amplifier to the first input of the amplifier.

11. The detection signal processing apparatus of claim 9 or 10, wherein the amplifier protection circuitry is arranged to divert current flow away in response to a voltage associated with said at least one of the inputs exceeding a threshold voltage, optionally wherein the threshold voltage comprises a voltage associated with the other input.

12. The detection signal processing apparatus of any preceding claim, further comprising a voltage source selectively operable to apply a reset pulse into the ringing circuitry to cause the ringing circuitry to provide voltage oscillations at the at least one of the inputs capacitively coupled to the ringing circuitry.

13. The detection signal processing apparatus of claim 12, as dependent on claim 4, wherein the reset pulse is selected so that some of the voltage oscillations have a magnitude which exceeds the threshold voltage.

14. The detection signal processing apparatus of claim 12 or 13, wherein the reset pulse is applied to provide a voltage transient above a threshold level, optionally wherein applying the reset pulse to provide a voltage transient above the threshold level comprises applying a selected voltage and then abruptly stopping applying that selected voltage.

15. The detection signal processing apparatus of any of claims 12 to 14, wherein the reset pulse comprises a voltage at a magnitude greater than a maximum output voltage for the amplifier.

16. The detection signal processing apparatus of any of claims 12 to 15, wherein theapparatus is configured to apply the reset pulse in the event that a saturation condition is detected for the amplifier.

17. The detection signal processing apparatus of any preceding claim, wherein the amplifier has a first input, a second input, and an output; and wherein the integration capacitor is coupled between the second input and the output, optionally wherein the ringing circuitry is capacitively coupled to the second input of the amplifier, optionally wherein the first input is a non-inverting input and the second input is an inverting input.

18. The detection signal processing apparatus of claim 17, wherein a first plate of the integration capacitor is coupled to the second input, and a second plate of the integration capacitor is coupled to the output of the amplifier, optionally wherein an inductance and a capacitance of the ringing circuitry are arranged in parallel between the second plate of the integration capacitor and the output of the amplifier.

19. The detection signal processing apparatus of any preceding claim, wherein the apparatus is configured to receive detection signals from an ion mobility spectrometer.

20. A detection apparatus for detecting the presence of a substance of interest in a sample, the apparatus comprising: a detector configured to provide detection signals for the sample indicative of substance detection performed by the detector; and a detection signal processing apparatus for processing the detection signals from the detector, wherein the detection signal processing apparatus comprises: an amplifier and an integration capacitor, the amplifier having inputs, with at least one input being connected to receive the detection signals from the detector; and ringing circuitry capacitively coupled to at least one of the inputs of the amplifier and being selectively operable to apply a ringing signal to said at least one of the inputs of the amplifier to cause amplifier protection circuitry of the amplifier to reset the integration capacitor.

21. The detection apparatus of claim 20, wherein the detection signal processing apparatus comprises the detection signal processing apparatus of any of claims 1 to 19.

22. A method of operating a detection signal processing apparatus to process detectionsignals received from a detector for identifying the presence of one or more substances of interest in a sample, wherein the apparatus comprises: (i) a detection signal coupling arranged for receiving detection signals from the detector, (ii) an amplifier and an integration capacitor, the amplifier having inputs, with at least one input being connected to the detection signal coupling, and (iii) ringing circuitry capacitively coupled to at least one of the inputs of the amplifier, wherein the method comprises: capacitively coupling a ringing signal to said at least one of the inputs of the amplifier to cause amplifier protection circuitry of the amplifier to reset the integration capacitor.

23. The method of claim 22, wherein the method comprises receiving a first detection signal from the detector and operating the amplifier to integrate said detection signal to provide an output signal indicative of the presence of the substance of interest in the sample; and wherein the ringing signal is applied to reset the integration capacitor prior to receiving and integrating a second detection signal from the detector, optionally wherein applying the ringing signal comprises applying the ringing signal in the event that a saturation condition is detected for the integration capacitor.

24. A method of operating a detection apparatus for detecting the presence of a substance of interest in a sample, wherein the apparatus comprises: a detector for providing detection signals for the sample indicative of substance detection performed by the detector, and a detection signal processing apparatus for processing the detection signals from the detector, the detection signal processing apparatus comprising: (i) an amplifier and an integration capacitor, the amplifier having inputs, with at least one input being connected to receive detection signals from the detector, and (ii) ringing circuitry capacitively coupled to at least one of the inputs of the amplifier, wherein the method comprises: capacitively coupling a ringing signal to said at least one of the inputs of the amplifier to cause amplifier protection circuitry of the amplifier to conduct, changing the charge within the capacitive coupling and upon removal of the ringing signal, reset the integration capacitor.

25. A computer program product comprising computer program instructions configured to program a voltage source to apply a voltage pulse into ringing circuitry of an apparatus to cause the apparatus to perform the method of any of claims 22 to 24.

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