CA1256493A - High purity water calibrating device - Google Patents

High purity water calibrating device

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Publication number
CA1256493A
CA1256493A CA000537584A CA537584A CA1256493A CA 1256493 A CA1256493 A CA 1256493A CA 000537584 A CA000537584 A CA 000537584A CA 537584 A CA537584 A CA 537584A CA 1256493 A CA1256493 A CA 1256493A
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Canada
Prior art keywords
conductivity
flow line
pure water
line means
cell
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA000537584A
Other languages
French (fr)
Inventor
Gregory Dzula
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Beckman Industrial Corp
Original Assignee
Beckman Industrial Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Beckman Industrial Corp filed Critical Beckman Industrial Corp
Priority to CA000537584A priority Critical patent/CA1256493A/en
Application granted granted Critical
Publication of CA1256493A publication Critical patent/CA1256493A/en
Expired legal-status Critical Current

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Abstract

ABSTRACT OF THE DISCLOSURE
Apparatus for calibrating a conductivity instrument having a conductivity cell and d conductivity measuring instrument operatively associated with the conductivity cell, includes a conduit for supplying high purity water to be measured; a first flow line for supplying the high purity water from the conduit to the conductivity cell; a second flow line for supplying the high purity water from the conduit to the conductivity cell; a mixed bed ion exchanger in the second flow line for de-ionizing the high purity water flowing through the second flow line; and a valve which selectively supplies the high purity water to the conductivity cell, from either the first flow line to provide a conductivity measurement of the high purity water or the second flow line to calibrate the conductivity cell.

Description

~S~33 The present invention relates to conductivity instruments and, more parti.cularly, is directed to apparatus for calibrating a conductivity instrument used to measure the conductivi-ty of pure water.
In many i.nstances, it is necessary to utilize high purity water. In order to ensure that the water is of sufficient purity, conducti.vity instruments are provided for measuring the conductivity of the high purity wa-ter.
These instruments are extremely sensitive, producing conductivity measurements having a sensitivity of more than one part in sixteen thousand, that is, at least 10 4. It therefore becomes extremely i.mportant that the conductivity cell of the calibrating i.nstrument be calibrated prior to such conductivity measurements.
The greatest problem wi.th the measurement of conducti.vity is the determination of the cell constant.
Even if the cell constant is determi.ned accurately when manufactured, it can only reliably be cali.brated to within 0.5-1.0%. When placed in use, the value of the cell constant can change for various reasons, i.ncluding the proximity of other metals, and usage. Further, the surfaces of the electrodes of the conductivity cell become contami-nated after use and increase the cell constant.
Various systems have been devised for calibrating or standardizing test cells of a monitoring system. For example, U.S. Patent No. 4,151,255, di.scloses a method for standardi.zing tes-t cells of a monitoring system. In normal operation, a sample is fed into a vessel which contains three elec-trodes. One electrode is a glass electrode for measuring the pH of the sample fluid contained within the vessel. Another electrode i.s a reference electrode for use i.n such measurement and the third electrode is a temperature sensing electrode which compensates for variati.ons of tempe-rature of the sample fluid fed to the vessel.

In order to assure tha~ the monitoring and measur-ing analyzer provides an accurate measurement of the pH of the fluid sample from the process, a buffer solution of known pH is fed to the vessel of -the test chamber. However, this patent requires two buffer storage means for holding two different standard buffer solutions for use in standardizing the reading of the pH measuring means during intermittent buffer standardization. The s-torage of different buffer solutions, and the necessary supply lines and valves associated therewith, makes this apparatus relatively expensive and complicated.
U.S. Patent No. 4,445,091 discloses a system for determining the p~ value of deionized cooling water by conductivity measurements, which includes a main loop and at least one parallel loop which includes an ion exchanger so that the two conductivity cells can be utilized by different measurement to provide a true measurement of the deionized water in the system. These ion exchangers fix the standard for one conductivity cell so that the measured difference between the two conductivity cells will corres-pond to the actual pH value of the deionized water in the system being measured. This patent, however, does not supply the cali.brated water and water to be measured to the same conductivity cell. Rather, two different conductivity cells are used and an adjustment must be made based on calibration of only one of the cells, thereby making this system relatively complicated and expensive, because of the additional conductivi.ty cell that i.s requi.red.
U.S. Patent No. 4,357,143 shows a parallel flow system in whi.ch one porti.on of the sample water is passed through an ion exchange resin column and then the two samples are passed to a detection cell which has two ion specific elec-trodes therein connected through conventional bri.dge circuitry. The di.fferential between the two cells is measured for the system. Thus, the use of two cells in this patent is similar to that of U.S. Pa-tent No. 4,445,091.

~Z~4~3~

Attenti.on is also directed to U.S. Patent Nos.
1,684,645; 3,451,403; and 4,473,458.
Accordingly, i.t is an object of -the present invention to provide apparatus for cali.brating the conductivity cell of a high purity water conductivity instrument.
It is another object of the present invention to provide apparatus for easily and readily calibra-ting a high purity water conductivity instrument prior to measure-ment.
It is still another object of the present inven-tion to provide apparatus for calibrating a high purity water conductivity instrumen-t that does not require the storage of separate calibrating solutions.
It is yet another object of the present invention to provide apparatus for calibrating a high purity water conductivity instrument by using a single conductivity cell.
It is a further object of the present invention to provide apparatus for calibrating a high purity water conductivity i.nstrument with the same high purity water that is to be measured.
In accordance with an aspect of the present invention, apparatus for calibrating a conductivity instru-ment having a conductivi-ty cell and a conductivity measuring instrument operatively associated with -the conductivity cell, includes:
(a) conduit means for supplying pure water to be measured by the conductivity instrument;
(b) first f],ow line means for supplying the pure water from the conduit means to the conductivity cell, (c) second flow line means for supplying the pure water from the conduit means to the conductivity cell;
(d) ion exchange means in the second flow line means for de-ioni~ing the pure water flowing -through the second flow line means; and (e) valve means for selectively supplying the pure water to the conductivity cell, from one of:
(i) the first flow line means to provide a conductivity measurement of the pure water; and (ii) the second flow line means to calibrate the conductivity cell, and (f) recirculation means connected to said second flow line means for recirculating at least a portion of the pure water flowing through said second flow-line means and the ion exchange means to maintain . the same. at its highest purity at all times.
In accordance with another aspect of the present invention, a method for calibrating a conductivity instrument having a conductivity cell and a conductivity measuring instrument pperatively associated with the conductivity cell, includes the steps of:
(a) supplying pure water to be measured by the co,nductivity instrument to conduit means;
(b) supplying the pure wa-ter from the conduit means to first flow line means;

(c) supplying the pure water from the conduit means to second flow line means;
(d) de-ioniæing the pure water flowiny through the second flow line means by ion exchanye means; and (e) selectively supplying the pure water to the conductivity cell, from one of:
(i) the first flow line means to provide a conductivity measurement of the pure water; and (ii) the second flow line means to calibrate the conductivity cell, and (f) recirculating at least a portion of -the pure water through the second flow line means and the ion-exchanging means to maintain the same at its highest purity.
The above and other, objects, features and advantages of the present invention will become readily apparent from the followin~ detailed description thereof which is to be read in connection with the accompanying drawings.
The only FIGURE of the drawings is a schematic flow diagram of apparatus for calibrating a high purity water conductivity instrument according to the present invention.
Referring to the single FIGURE of the drawings, a conductivity instrument 10 is shown for measuring the conductivity of high purity water. The conductivity instrument 10 includes a conductivity cell 12 to which the high purity water is supplied and a conductivity measuring instrument 14 connected to conductivity cell 12 for determining the conductivity of the high purity water., Conductivity cell 12 is a conventional d~vice and includes a vessel with a plurality of electrodes therein which are sensitive to the conductivity of the high purity water.
The electrodes supply an electrical signal to the conduc-tivity measuring instrument 14, which is also conventional.
Conductivity measuring instrument 14 includes a display 16 and a control knob 18 for adjus-ting -the display output.
Display 16 may be an analog display, as shown, including a pointer and scale, or alternatively, may be a digital di.splay.
In accordance with the present invention, apparatus 20 for calibrating conductivity instrument 10 includes a first flow line 22 supplied with high purity water from a high purity water supply 24 and a second flow line 26 also supplied with such high purity water from high purity water supply 24. A mixed bed ion exchanger 28 is connected in second flow line 26 so as to deionize the high purity water flowing therethrough.
Apparatus 20 further includes a valve, shown schematically at 30, which selectively supplies the high purity water from first flow line 22 or second flow line 26 to eondueti.vity eell 12. In this regard, valve 30 can be manually actuated, or automatically actuated by a servo control 32, as shown.
In the basic operation, valve 30 is actuated to supply high purity water from seeond flow line 26 to eondue-tivi.ty eell 12. Thus, the hi.gh purity water from supply 24 is supplied through mi.xed bed ion exchanger 28 where it i.s deionized and then supplied to conduetivity cell 12. To cali.brate conductivity instrument 10, conductivity measuring i.nstrument 14 is then adjusted by control knob 18 sueh that display 16 has a reading of 18.3 Megohms which is the theoretieal maxi.mum speei.fi.c eonduetivity of pure water.
Thereafter, valve 30 i.s rotated such that hi.gh puri.ty water from hi.gh puri.ty water supply 24 i.s supplied through fi.rst flow line 22 to condueti.vity cell 12, whereby eonduetivi.ty measuring i.nstrument 14 wi.ll then accurately read the purity of the water from high purity wa-ter supply 24.

In this regard, the same water that is to be measured is used to calibrate conductivi-ty instrument 10.
At the same time, only a single conductivity cell 12 is required for such calibration, thereby reducing the complexity and cost of the apparatus.
Various modifications can be made to the present i.nventi.on by one of ordinary skill in the art. For example, valve 30 may be an electromagnetically operated valve which is controlled by a sequencing or timing system 32. The sequencing or timing system 32 will provide automatic calibration by periodically controlling valve 30 to supply high purity water through mixed bed ion exchanger 28 to conductivity cell 12.
In addition, the calibrated value could be stored in an electroni.c or other suitable memory unit 34, whereby subsequent or later readings can be compared with this calibrated reading. Memory uni.t 34 may simply be a capacitor that is charged to a parti.cular voltage, or alternatively, may be more complex and thus include a digital memory. In this latter device, the calibrated reading from conductivity measuring instrument 14 would be supplied through an analog-to-digital (A/D) converter 36 to memory unit 34, and return from memory unit 34 to conductivity measuring i.nstrument 14 through a di.gital-to-analog (D/A) converter 38, as shown.
In such case, suitable READ/WRI~E circuitry would be provided for accessing the information in memory 34.
Still further, a depletion indicator 40 can be associated with the mixed bed i.on exchanger 28 to indicate depletion of the mixed bed ion exchange resin therein, to prevent erroneous readings. Deple-tion i.ndicator 40 may take the form of color indicating resins, or alternatively, may be more complex and include an alarm which is acti.va-ted when the conductivity readingsof water through mixed bed i.on exchanger 28 are close to the conductivity readings of water flowing through first flow line 22.

~ fur-ther i.mprovement upon the apparatus could be the use of a recirculating standardizing scheme, in which thestandardized water which has already passed through mi.xed bed ion exchanger 28 is continuously recirculated back through mixed bed ion exchanger 28 to maintain the water at its highest puri.ty at all times. Specifically, a portion of the high puri.ty water which has passed through mixed bed ion exchanger 26 will flow through first auxiliary flow line 42 to a fluid pump 44 which pumps the fluid through a second auxi.liary flow line 46 to the input of mixed bed ion exchanger 28. In such case, a three-way valve 48 can be provided atthe input of mixed bed ion exchanger 28 for selectively supplying the fluid thereto from high purity water supply 24 or second auxiliary flow line 46. In this regard, servo control system 32 could be used to actuate pump 44 and to rotate three-way valve 48 at a time when valve 30 is ro-tated to permit flow between first flow li.ne 22 and conductivity cell 12, as shown.
Further, it i.s preferable that first Elow line 22 and second flow line 26 are placed in close proximity to each other to minimize problems associ.ated with temperature compensation of high puri.ty water.
Having descri.bed specific preferred embodiments of the invention with reference to the accompanying drawings, it will be understood that the present invention is not limited to these precise embodiments, and that vari.ous changes and modi.fications may be effected by one of ord.inary skill i.n the art wi.thout departing from the scope and spirit of the inven-tion as defined by the appended clai.ms.

Claims (6)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. Apparatus for calibrating a conductivity instrument having a conductivity cell and a conductivity measuring instrument operatively associated with said conductivity cell, said apparatus comprising:
a. conduit means for supplying pure water to be measured by said conductivity instrument;
b. first flow line means for supplying said pure water from said conduit means to said conductivity cell;
c. second flow line means for supplying said pure water from said conduit means to said conductivity cell;
d. ion exchange means in said second flow line means for de-ionizing said pure water flowing through said second flow line means;
e. valve means for selectively supplying said pure water to said conductivity cell, from one of:
i. said first flow line means to provide a conductivity measurement of said pure water; and ii. said second flow line means to calibrate said conductivity cell, and f. recirculation means connected to said second flow line means for recirculating at least a portion of the pure water flowing through said second flow line means and the ion exchange means to maintain the same at its highest purity at all times.
2. Apparatus according to claim 1, further including servo control means for controlling said valve means to periodically supply said pure water from said second flow line means to said conductivity cell.
3. Apparatus according to claim 1 wherein said conductivity measuring instrument produces a signal corresponding to the conductivity of said pure water supplied to said conductivity cell and further comprising memory means for storing the signal corresponding to the conductivity of pure water supplied from said second flow line means.
4. A method of calibrating a conductivity instrument having a conductivity cell and a conductivity measuring instrument operatively associated with said conductivity cell, comprising the steps of:
a. supplying pure water to be measured by said conductivity instrument through conduit means;
b. supplying said pure water from said conduit means to first flow line means;
c. supplying said pure water from said conduit means to second flow line means;
d. de-ionizing said pure water flowing through said second flow line means by ion exchange means;
e. selectively supplying the pure water to the conductivity cell, from one of:
i. said first flow line means to provide a conductivity measurement of said pure water; and ii. said second flow means to calibrate said conductivity cell, and f. recirculating at least a portion of said pure water through said second flow line means and said ion exchange means to maintain the same at its highest purity.
5. A method according claim 4 further comprising the step of periodically and automatically, selectively supplying said pure water to said conductivity cell, from one of:
a. said first flow line means; and b. said second flow line means.
6. A method according to claim 4 further comprising the step of storing in memory means a signal corresponding to the measured conductivity of said pure water from said second flow line means.
CA000537584A 1987-05-21 1987-05-21 High purity water calibrating device Expired CA1256493A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CA000537584A CA1256493A (en) 1987-05-21 1987-05-21 High purity water calibrating device

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CA000537584A CA1256493A (en) 1987-05-21 1987-05-21 High purity water calibrating device

Publications (1)

Publication Number Publication Date
CA1256493A true CA1256493A (en) 1989-06-27

Family

ID=4135715

Family Applications (1)

Application Number Title Priority Date Filing Date
CA000537584A Expired CA1256493A (en) 1987-05-21 1987-05-21 High purity water calibrating device

Country Status (1)

Country Link
CA (1) CA1256493A (en)

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