PHOTOIONIZATION DETECTOR SENSOR WITH ADJUSTABLE GAIN

Abstract

A photoionization detector sensor equipped with an adjustable gain amplifier, and method of standardizing output of the photoionization detector sensor by adjusting the gain so that an actual test value expected to produce a known anticipated value matches the anticipated value.

Claims

1. A photoionization detector sensor equipped with an adjustable gain amplifier.

2. A photoionization detector sensor having (i) an ultraviolet lamp operable for ionizing a target analyte within a sample, (ii) electrodes 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, and (iii) an amplifier in electrical communication with the electrodes for receiving the generated current signal and amplifying the current signal via an adjustable gain to create an amplified electrical signal proportional to the concentration of target analyte within the sample.

3. The photoionization detector sensor of claim 2 wherein 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.

4. The photoionization detector sensor of claim 2 wherein the ultraviolet lamp is operable for ionizing a volatile organic compound target analyte.

5. A photoionization detector sensor having (i) a housing defining a sample retention chamber, (ii) an ultraviolet lamp operable for ionizing a target analyte within the sample retention chamber, (iii) an anode-cathode pair for detecting the presence of ionized target analyte within the sample retention chamber and generating a current proportional to the concentration of target analyte within the sample retention chamber, and (iv) a two-stage transimpedance amplifier in electrical communication with the anode-cathode pair for receiving the generated current and having an inverting current to voltage first stage to create an electrical signal having a voltage proportional to the concentration of target analyte within the sample, and a non-inverting voltage gain second stage equipped with a nonvolatile digital potentiometer operable for adjusting the voltage gain to create an amplified and adjusted electrical signal proportional to the concentration of target analyte within the sample.

6. The photoionization detector sensor of claim 5 wherein the ultraviolet lamp is operable for ionizing a volatile organic compound target analyte.

7. A method of standardizing output of a photoionization detector sensor in accordance with claim 2, comprising 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.

8. A method of standardizing output of a photoionization detector sensor in accordance with claim 5, comprising 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 non-inverting voltage gain second stage of the two-stage transimpedance amplifier so that the gain-adjusted test value matches the anticipated value.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is a schematic view of one embodiment of the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0009]

TABLE-US-00001 Nomenclature Table REF. NO. DESCRIPTION 100 Photoionization Detector Sensor 110 Housing 119 Sample Retention Chamber 119.sub.1 Sample Intake Port 119.sub.2 Sample Venting Port 120 UV Lamp 130 Electrodes 130.sub.1 First Electrode or Anode 130.sub.2 Second Electrode or Cathode 140 Amplifier with Adjustable Gain 150 Processor S.sub.1 Current Signal from Electrodes S.sub.2 Amplified and Gain Adjusted Signal from Amplifier A Target Analyte

Construction

[0010] Referring to FIG. 1, the invention is a photoionization detector sensor 100 equipped with an adjustable gain amplifier 140.

[0011] 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 130.sub.1 and a cathode 130.sub.2) for detecting the ions and generating a first electrical current signal S.sub.1 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 S.sub.1 and amplifying and converting the first electrical current signal S.sub.1 to a second voltage electrical signal S.sub.2. 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 119.sub.1 and optionally a sample venting port 119.sub.2.

[0012] Photoionization detector sensors 100 are employed in instruments that typically include a processor 150 for receiving the amplified electronic signal S.sub.2, converting the value of the amplified electronic signal S.sub.2 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.

[0013] 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.

[0014] The photoionization detector sensor 100 is particularly adapted to detect and quantify the concentration of volatile organic compounds in a sample.

Factory Standardization

[0015] 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 S.sub.2 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.