Conductivity meters

The war itself also drove the development of improved and miniaturised electronic components for creating oscillators and amplifiers and, ultimately, semiconductors, which made practical the electronic systems needed in portable eddy current test instruments. The refinement of those systems continues to the present day and advances continue to be triggered by performance improvements of components and systems. In the same way that today s pocket calculator outperforms the large, hot room full of intercormected thermionic valves that I first saw in the 50 s, so it is with eddy current instrumentation. Today s handheld eddy current inspection instrument is a powerful tool which has the capability needed in a crack detector, corrosion detector, metal sorter, conductivity meter, coating thickness meter and so on. 

See 2-3.1. Typical laboratory conductivity meters have insufficient sensitivity to measure semiconductive and nonconductive liquids, in Appendix B, some tabulated conductivities appear as < suggesting that the instmment used was inappropriate. Some liquids listed as conductive might fall instead into the semiconductive category (e.g., cymene). Eor conductivities less than 100 pS/m especially, highly sensitive picoammeters are required to measure the small currents involved and great care is needed to avoid contamination of both the sample and the test cell. Several ASTM methods are available according to the conductivity range involved [143-146]. 

Purification of Antibiotic 66-40 — Dissolve 28 g of crude Antibiotic 66-40 in 100 ml of distilled water and charge to an anion exchange adsorption column (Dowex 1 X2) in the hydroxyl form. Slurry 2,000 g of the resin in water in to a column 2yj in diameter and 36 "high. Elute the column with distilled water at a rate of about 23 ml/min collecting 100 ml fractions and monitor with a conductivity meter and by disc testing against Staphylococcus aureus. 

The run and regeneration cycle on small to medium-size units is normally governed by a multi-port valve, which is the only moving part required. There have been many cases where this has failed and brine was injected directly into the boiler. A conductivity meter on the make-up line would guard against this. 

As already indicated conductimetric measurements are normally made with alternating current of frequency 103Hz, and this leads to the existence of capacitance as well as resistance in the conductivity cell. If the frequency of the current is increased further to 106 — 107 Hz, the capacitance effect becomes even more marked, and the normal conductivity meter is no longer suitable for measuring the conductance. 

NOTE This chart assumes oxygen scavenger, polymer, and other necessary water chemistry controls are in place. If determining TDS via a conductivity meter, use an un-neutralized sample. 

Figure 10 Separation of monochloroacetate, dichloroacetate, and trichloroacetate on a sulfonated poly(styrene-divinyl benzene) column with suppressed conductivity detection. Column 2% cross-linked sulfonated poly(styrene-divinyl benzene) capacity 0.02 meq/g. Flow rate 64 ml/hr. Eluant 15 mM sodium phenate. Suppressor 0.28 x 25 cm Dowex 50W X8 column (200-400 mesh). Detector Chromatronix conductivity cell connected to a Dow conductivity meter. (Reprinted with permission from Small, H., Stevens, T. S., and Bauman, W. C., Anal. Chem., 47,1801,1975. 1975 Analytical Chemistry.)...

In this series of instruments for analytical electrochemistry, Philips also supplies the microprocessor-controlled PW 9527 digital conductivity meter with 16 push-buttons and on the rear an analogue output for connection to a recorder and a 25-way connector providing a two-way RS 232 serial connection (see Philips leaflet 9498 362 9326). 

For conductimetric incremental titrations, large rugged analogue conductivity meters have also become available, e.g., the Metrohm 518 conductometer (in connection with the Model 536 potentiograph its yields a rapid recording of the curve together with end-point indication) and the Philips PW 9505 analogue conductivity meter (in addition to a recorder output and an output for electrode re-platinization, there is a choice of manual or, by use of a Pt 100 resistance thermometer, automatic temperature compensation). 

Monitoring (using pH meters or conductivity meters) the process baths can determine the need for bath replenishment. 

Fig. 7.1 Experimental set up for sonochemical carbonization experiments [24] (1) Ultrasound Probe, (2) C02 gas sparger, (3) Conductivity meter, (4) pH meter, (5) C02 gas cylinder, (6) C02 gas flow meter, (7) Air flow meter, ( ) Air compressor (9) Magnetic stirrer, (10) Ca(OH)2 slurry...

UV spectra of these solutions were recorded and the concentration of zinc was measured from the absorbance value and the results obtained have been shown in Table 9.11. In another experiment, the nephelometric and conductometric analysis were carried out but only after diluting the solutions from 5 to 1 M of NaOH, since the conductivity of solutions above this concentration was beyond the scale of the conductivity meter. 

The conductance of a solution is the inverse of its resistance, and conductance has units of ohms 1 or mohs. The higher the conductance of a solution, the lower is its electrical resistance. A conductivity meter and conductivity cell are used to determine the effective resistance of a solution. The conductivity cell consists of a pair of platinized platinum electrodes with an area of approximately 1.0 cm2 with spacers designed to hold the electrodes rigidly parallel and at a fixed distance from each other. The cell can be standardized with solutions of known conductivity to obtain the cell constant, k so that the instrument response R... 

Classical conductivity meters are forms of the Wheatstone bridge. The Wheatstone bridge is a null device. It produces an off-balance potential when the four resistances making up the bridge do not satisfy the null condition in the following equation. 

The output from the Grapple linear resistance bridge [7] was fed to a chart-recorder. For the experiments with styrene and indene, an instrument with a maximum speed of 20 cm-min 1 was used, but for the vinyl ethers a faster instrument with a maximum chart speed of 100 cm-min 1 was required. The signal from a WPA Scientific Instrument CMD 400 digital conductivity meter was fed to another recorder. At the end of each experiment, the electrical conductivity, Kf, of the reaction mixture was determined accurately with a Wayne-Kerr Autobalance bridge. 

Conductivity was measured as described (10) using a conductivity meter (Radiometer, Copenhagen, Denmark) type CDM3 equipped with a CDC 304 immersion electrode with manual temperature compensator type CDA 100. The instrument was calibrated as specified by the manufacturer. The determination of the (NH4)2S04 concentration from the conductivity measurements was done at constant temperature (4°C) using a calibration curve, in the range of 0.016 mM to 120 mM AS in glucose or sucrose (total... 

Using the 100-mL graduated cylinder, measure 70 mL of distilled water into the 150-mL beaker. Raise the beaker until the conductivity probe is in the water. After the conductivity meter stabilizes, press TRIGGER on the CBL unit. 

Figure 8. Diffusive permeability measurement system (1) thermostated bath (2) diffusion cell (3) membrane (4) thermometer (5) stirrer (6) circulation pump (7) conductivity cell (8) conductivity meter (9) recorder.

The conductivity measurement was performed at 25 C by a conductivity meter MODEL CM-30ET(TOA Electronics Ltd.). 

Fig. 3.20. Common conductivity probe for vacuum work. A couplings to shielded cables from conductivity meter 5 a B. 19 or B.24 socket fitting onto cone on observation/reaction vessel C graded-seal soda glass to borosilicate glass D shielded leads spot-welded to thick Pt wires E sealed through the soda glass probe and held together by the lead glass bead F.

For monitoring system performance, a conductivity meter should be present or built in the water system for continuous measurement of the conductivity. If this device is not available, samples must be taken manually and measured respectively. 

Analyses were done on a Dionex Model 14 Ion Chromatograph (IC), equipped with a Waters WISP 7 autosampler, Linear recorder, and interfaced with a Hewlett-Packard 3354 Laboratory Automated System. The principal components of the IC, shown in Figure 2, are (A) eluent reservoir, (B) pump, (C) injection valve, (D) separator column, (E) suppressor column, (F) conductivity cell, and (G) conductance meter with a recorder (integrator). 

A conductivity meter setting of 10 pmhos is appropriate for most samples. If bromide or nitrate at two times the OSHA standard levels or chloride are being analyzed, the less sensitive setting of 30 ymho/cm may be used. 

Besides a DC power supply, the AQUATECH System is comprised of conventional pumps, storage and recycle tanks, heat exchanger and piping. The major instruments typically include a pH analyzer, conductivity meter and concentration monitor. 

Conductivity Meter. A second system utilizes a simple ohmmeter circuit, shown in Fig. 3. A meter, transformer secondary winding, and conductivity cell are connected in series so that the current is a function of the cell conductance. The meter may be calibrated in resistivity or conductivity units. 

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