Patent Application
20240313733
Photoionization detector (PID) sensors break molecules, typically volatile organic molecules, into positively charged ions and free electrons using high-energy ultraviolet (UV) radiation. As target analyte enters the detector, they are bombarded by high-energy UV photons. The target analyte absorbs the UV light, resulting in ejection of electrons and the formation of positively charged ions. The positively charged ions are sensed by an anode/cathode arrangement in the detector and produce an electric current whose amplitude is proportional to the positively charged ions produced (i.e., the greater the concentration of target analyte in the sample entering the detector the more positively charged ions produced resulting in a greater current). The current is amplified, displayed on an ammeter, or converted via a look-up table to a concentration of target molecules and digitally displayed.
Manufacturing variances often result in small but meaningful variances in the output of the PID sensors, even amongst those in the same manufactured batch or lot. This requires customers to perform an initial calibration of the PID sensor after placement of the sensor in the customer's instrument.
Hence, a substantial need exists for an OEM PID sensor that eliminates or compensates for manufacturing variances whereby the output of the OEM PID sensor is consistent from sensor to sensor as delivered to customers so as to eliminate the need for customers to perform an initial calibration of the PID sensor after placement of the sensor in the customer's instrument.
A first aspect is a photoionization detector sensor equipped with an adjustable gain amplifier. The photoionization detector sensor includes an ultraviolet lamp, electrodes (e.g., an anode-cathode pair), and a signal amplifier. The ultraviolet lamp is operable for ionizing a target analyte within a sample. The electrodes are operable for detecting the presence of ionized target analyte within the sample and generating a current signal proportional to the concentration of target analyte within the sample. The amplifier is in electrical communication with the electrodes for receiving the generated current signal and amplifying the current signal for creating an amplified electrical signal proportional to the concentration of target analyte within the sample. The amplifier includes an adjustable gain feature for allowing the amplified electrical signal output to be standardized to correct for any manufacturing-imposed variance in the current signal generated by the electrodes and transmitted to the amplifier.
A preferred option for the amplifier is a two-stage transimpedance amplifier having an inverting current to voltage first stage and a non-inverting voltage gain second stage wherein the second stage is equipped with a nonvolatile digital potentiometer operable for adjusting the voltage gain.
The photoionization detector sensor can include a housing defining a sample retention chamber operable for holding the sample, the ultraviolet lamp operable for ionizing target analyte within the sample held within the retention chamber, and the electrodes operable for detecting the presence of ionized target analyte within the sample retention chamber.
A second aspect is a method of standardizing output of the photoionization detector sensor in accordance with the first aspect. The method involves the steps of (A) activating the photoionization detector sensor to detect target analyte in a sample to create an amplified electrical signal having a test value, wherein the sample has a known concentration of the target analyte and is expected to generate an amplified electrical signal of known anticipated value, (B) comparing the test value and the anticipated value, and (C) standardizing output of the photoionization detector sensor by adjusting the gain imposed by the amplifier so that the gain-adjusted test value matches the anticipated value.
Referring to
Photoionization detector sensors 100 have an ultraviolet (UV) lamp 120 for ionizing target analyte A within a sample, a pair of electrodes 130 (i.e., an anode 1301 and a cathode 1302) for detecting the ions and generating a first electrical current signal S1 proportional to the concentration of target analyte A within the sample, and an amplifier 140 in electrical communication with the electrodes 130 for receiving the generated first electrical current signal S1 and amplifying and converting the first electrical current signal S1 to a second voltage electrical signal S2. These components are generally retained within a housing 110 that defines a sample retention chamber 119 positioned to receive UV radiation emitted by the UV lamp 120 upon excitation of the lamp 120 and having a sample intake port 1191 and optionally a sample venting port 1192.
Photoionization detector sensors 100 are employed in instruments that typically include a processor 150 for receiving the amplified electronic signal S2, converting the value of the amplified electronic signal S2 to a concentration of target analyte A in the sample based upon an algorithm or a lookup table, and displaying or otherwise reporting the concentration.
The photoionization detector sensor 100 of the present invention has an adjustable gain amplifier 140, such as a two-stage transimpedance amplifier with an inverting current to voltage first stage and a non-inverting voltage gain second stage, wherein the second stage is equipped with a nonvolatile digital potentiometer operable for adjusting the voltage gain.
The photoionization detector sensor 100 is particularly adapted to detect and quantify the concentration of volatile organic compounds in a sample.
The method of standardizing output of the photoionization detector sensor 100 includes the steps of (A) activating the photoionization detector sensor 100 to detect target analyte A in a sample to create an amplified electrical signal S2 having a test value, wherein the sample has a known concentration of the target analyte A and is expected to generate an amplified electrical signal of known anticipated value, (B) comparing the test value and the anticipated value, and (C) standardizing output of the photoionization detector sensor 100 by adjusting the gain imposed by the amplifier 140 so that the gain-adjusted test value matches the anticipated value.
