CN202676656U

CN202676656U - Device for measuring gas concentration through electrochemical sensor

Info

Publication number: CN202676656U
Application number: CN 201220295838
Authority: CN
Inventors: 谢雷; 韩杰; 沈立军; 韩益苹
Original assignee: SHANGWO MEDICAL ELECTRONIC WUXI CO Ltd
Current assignee: Sunvou Medical Electronics Co ltd
Priority date: 2012-06-21
Filing date: 2012-06-21
Publication date: 2013-01-16
Anticipated expiration: 2022-06-21

Abstract

The utility model discloses a device for measuring gas concentration through an electrochemical sensor. The device consists of a sample chamber, a small gas chamber, the electrochemical sensor, a pump and a valve, wherein the sample chamber, the electrochemical sensor, the pump and the valve are connected to form a circulating gas circuit through pipelines; in the circulating gas circuit, the electrochemical sensor is connected in series with the pump, and the other ends of the pump and the electrochemical sensor which are connected in series are connected in parallel with the small gas chamber through the valve; the size of the small gas chamber is smaller than one tenth of that of the sample chamber; the sample chamber is a slender pipeline; the volume of the sample chamber is over 95 percent of that of the circulating gas circuit; when a gas is analyzed, the gas flows in the sample chamber in a piston flow mode; the sample chamber is used for storing a fluid sample to be analyzed; the electrochemical sensor is closed in a circulating fluid circuit and is used for measuring a respond signal and electrolyzing electrochemical active components to be measured; and the pump is used for driving fluid to flow in the circulating fluid circuit circularly, so that the fluid can pass through the sensor at least twice.

Description

A kind of device that utilizes the electrochemical sensor measure gas concentrations

Technical field

The utility model relates to the device of material concentration in the measurement gas.

Background technology

During with the electrochemical gas sensor measure gas concentrations, its signal S satisfies following measurement equation usually:

S?=?kC ₀?+?k ₀ （1）

Wherein, parameter k and k ₀Be respectively zero point and the sensitivity parameter of a sensor.

Sensor in use its response signal can be subject to comprising airflow rate, pressure, temperature, the impact of humidity and other interference gas component, and transducer sensitivity also can be owing to aging, inactivation, activation or the impact such as poisoning and change, thereby the use of sensor generally all requires in the airflow rate approaching with service condition, pressure, temperature, humidity and gas composition, utilize at least two known standard models of concentration that sensor is demarcated under the condition, demarcate with k(with applicability and two the parameter k that determine equation (1)), and nominal time and Measuring Time are approaching to avoid above-mentioned interference as far as possible.

Also there is a series of problem in above-mentioned calibration process in actual application, as: the calibration samples such as low concentration, high volatile volatile, high reaction activity and high risk (poisonous and harmful is inflammable and explosive) are difficult for preparing, store, carry or using, and have technology and security risk; Calibration sample and demarcation condition are difficult to simulating actual conditions usually, have reliable and validity risk; Can simulating actual conditions even if demarcate, but some use scene also is difficult to carry out proving operation; Even if can on-site proving operation, but many users also usually ignore and demarcate use.

For example, the calibration sample of the organic volatile such as formaldehyde, benzene just is difficult to obtain or use; Even if in the industry that is most widely used and Environmental safety supervision field, especially colliery and the defeated place of waiting of oil gathering, also be difficult to on-site proving, ignore or the wrong report that improper demarcation causes or the then often generation of security incident of not reporting; Especially civil area leaks early warning etc. such as household person with blood sugar test and indoor fuel gas, and the user seldom demarcates, and the problem that causes thus also often has report.

The effort that addresses this problem at present mainly provides safety, convenient and reliable automatic Calibration instrument.For example, Honeywell discloses the patent (US7975525B2 of multinomial transducer calibration and self-calibrating method recent years, US7661290B2, US2006/0266097A1, US2005/0262924A1, US7401493B2, US7581425B2, US7655186B2, US7071386B2, US6918281, US2006/0042351A1), Drager also discloses several transducer calibration patents (US7704356B2, US7645362B2) recently, a common ground of these patents is exactly that they all need calibrating gas, and the method that just produces calibrating gas is had nothing in common with each other.Is there there the scaling method that does not need calibrating gas?

1987 and City Tech in 1989 and Drager are disclosing respectively the patent (US4829809 that does not rely on calibration sample to demarcate, US4833909), an electrochemical sensor is placed in the closed container that is full of sample, after allowing the measured matter electrolysis totally, determine gas concentration by the coulomb electrolytic process, and then sensor is demarcated.

Industrial Scientific discloses a patent (US6055840) in 2000, a kind of method of finding the solution gas concentration by quantitative adjusting control gas diffusion paths resistance has been described, the method need to be known the coefficient of diffusion of gas to be measured and the physical size of at least one gas diffusion paths, thereby practical application is also inconvenient.

Yet these also belong to laboratory study or analytical approach, are difficult to practical application.At present, the method for using the normal concentration material that provided by standard metering department to demarcate also is provided always in the demarcation of gas sensor.

Summary of the invention

The utility model will disclose a kind of device that utilizes electrochemical sensor to build the direct measure gas concentrations of cycle analysis gas circuit.

This device is comprised of sample chamber, little air chamber, electrochemical sensor, pump and valve, it is characterized in that: described sample chamber, electrochemical sensor, pump and valve connect into the circulation gas circuit by pipeline, in the circulation gas circuit, electrochemical sensor and series connection of pumps are passed through valve in parallel one little air chamber at pump with the other end of electrochemical sensor, and its volume is less than 1/10 of the sample chamber; Described sample chamber is elongate conduit, and volume is greater than 95% of circulation gas circuit cumulative volume, and gas flowing therein is to be used for storing fluid sample to be analyzed by piston flow during analysis; Described electrochemical sensor is closed in the circulation stream, is used for measuring response signal and electrochemical activity component to be measured being carried out electrolysis; Described pump is used for propelling fluid and circulates at the circulation stream, can at least twice passes through sensor.

But this device in-site measurement sensor zero point and Calculation of Gas concentration, overcome the impact on measuring of temperature, humidity, pressure and part interference gas, realization need not sensor is demarcated to the direct measurement of gas concentration, has greatly improved the Stability and dependability of measuring.

Description of drawings

Fig. 1 is gas circuit structure schematic diagram of the present invention;

Embodiment:

Application Example one

Embodiment when now illustrating that in conjunction with Fig. 1 the utility model is used for gas concentration measurement: this device is by the sample chamber, electrochemical sensor, pump and valve form, described sample chamber 7, electrochemical sensor 6, pump 5,

valve

1,2,3,4 and pipeline connect into the closed circulation stream; Described pipeline refin tubule, the kapillary inner volume is less than 5% of circulation stream cumulative volume, preferably less than 1%; When described sample chamber structure can guarantee cycle analysis, gas flowing therein was piston flow, and its preferred structure is elongate conduit, and cumulative volume is greater than 95% of circulation stream cumulative volume, more preferably greater than 99%; Described electrochemical sensor is enclosed in the circulation stream, is used for measuring response signal and electrochemical activity component to be measured being carried out electrolysis, and described pump driving gas circulates in the circulation gas circuit, and the recyclegas flow velocity can obtain by air chamber volume and cycle period; Stingy chambers 8 in parallel are used for the sensor zero point in-site measurement by electrochemical sensor 6, pump 5 and

valve

3,4, and its volume is preferably less than 1/10 of sample chamber 7.

The actual measurement process was undertaken by following three steps:

(1) sampling: switch valve 1,2, by pump 9 with gas via valve 1, sample chamber 7, valve 2, pump 9 suction sample chambers 7.

(2) circulation is measured: switch by

valve

1,2,3,4, opening simultaneously air pump 5 allows sample make gas return air pump 5 and circulate through air pump 5, electrochemical sensor 6, valve 4, valve 2, sample chamber 7, valve 1, valve 2 in the effect of ebullator, carry out the secondary cycle analysis to measure, by electrolysis, the measurement equation that the response signal of sensor satisfies during its each circulation process sensor can be expressed as during gas process sensor:

i ₀=?kC ₀?+?k ₀ （2）

i ₁=?kC ₁?+?k ₀ （3）

I wherein ₀, i ₁Be the response current of double measurement sensor, k is transducer sensitivity, k ₀Be electric current at the bottom of the sensor, C ₀, C ₁Sample concentration when being respectively sample original concentration and the 2nd measurement, its unknown number has k, k ₀, C ₀, C ₁Four.

According to Faraday's law, sensor is measured the electrolysis sample at every turn and is caused its concentration change Relationship Quality equation can be expressed as:

nFV(C ₁-C ₀)?=?i ₀*t （4）

Wherein n is the reaction electron number, and F is that Faraday constant, V are the sample chamber volume, and t is cycle period.

(3) measure zero point: after finishing twice measurement,

switch valve

3,4 makes airflow direction become air pump 5, electrochemical sensor 6, valve 4, stingy chamber 8, valve 3, air pump 5, this moment, sensor exhausted the formula electrolysis to the active gases component gas in the partial circulating gas circuit, and the response signal of long enough sensor after the time will be close to response signal k at its zero point ₀

Reach the k that directly measures by simultaneous equations (2), (3), (4) like this ₀Can find the solution sample concentration C ₀And transducer sensitivity k.

Can be used for directly determining measured matter concentration by the visible the method for this embodiment, and need not before measurement, sensor to be demarcated; And the calibrating parameters of sensor (such as sensitivity and end electric current) also can be by the method direct solution out, and owing to being calculates the transducer calibration parameter in the actual measurement process, thereby the method can be described as a kind of self-calibrating method; In addition, what the method was used is the difference of twice response signal of sensor, can deduct temperature, pressure, flow and interfering material to the equal contribution of each measurement, therefore use the signal measurement that contains these contributions than classic method, have higher sensitivity, selectivity and stability.

The realization of the method has certain requirement to gas circuit structure, gas circuit resistance and transducer sensitivity, in general large and small cycles gas circuit resistance is basically identical, gas flow rate when guarantee is measured zero point like this and the flow velocity of measurement of concetration are basically identical, the selection of the sensitivity of sensor need to be satisfied two conditions in addition: the one, sensitivity suitable (can not be too large or too little), need to guarantee concentration gradient that the each circulation of when systemic circulation is analyzed gas causes change can differentiate and guarantee repeatedly loop test after concentration can not fall too lowly; The 2nd, guarantee that sensitivity is enough large under one the front topic, can be within enough short time the active gases of partial circulating gas circuit be exhausted.

The present embodiment 4 valve control airflow directions and break-make, obviously valve 1,3 can substitute with a two position three-way valve, and

valve

2,4 an also available two-position three-way valve substitutes to reduce the gas circuit package count.

Claims

1. device that utilizes the electrochemical sensor measure gas concentrations, formed by sample chamber, little air chamber, electrochemical sensor, pump and valve, it is characterized in that: described sample chamber, electrochemical sensor, pump and valve connect into the circulation gas circuit by pipeline, in the circulation gas circuit, and electrochemical sensor and series connection of pumps, pass through valve in parallel one little air chamber at pump with the other end of electrochemical sensor, its volume is less than 1/10 of the sample chamber; Described sample chamber is elongate conduit, and volume is greater than 95% of circulation gas circuit cumulative volume, and gas flowing therein is to be used for storing fluid sample to be analyzed by piston flow during analysis; Described electrochemical sensor is closed in the circulation stream, is used for measuring response signal and electrochemical activity component to be measured being carried out electrolysis; Described pump is used for propelling fluid and circulates at the circulation stream, can at least twice passes through sensor.