Leeds and Northrup

During the 1980s, several adaptive controllers were field-tested and commerciahzed in the U.S. and abroad, including products by ASEA (Sweden), Leeds and Northrup, Foxboro, and Sattcontrol. At the present time, some form of adaptive tuning is available on almost all PID controllers. The ASEA adaptive controller, Novatune, was... 

Apparatus. All electrical resistances were measured with an electrolytic conductivity bridge (Leeds and Northrup model 4666) which was constructed according to specifications set forth by Jones (28) and described by Dike (29). The audio-frequency source was a General Radio Co. type 1311-A audio oscillator used with the frequency regulated at 1000 Hz and the output at about 5 V. The detector circuit consisted of a high-gain low-noise tuned amplifier and null detector (General Radio Co. type 1232-A) and an oscilloscope (Heathkit model O-ll) ... 

All samples were analyzed in an AllTech 1/8"I.D, 20 foot column, packed with VZ-7 resin, using helium as the carrier gas. This column proved more effective for the measurement of the C4 components than the Poropak- N column. Ammonia was not detected by this column and as a result some of the assumptions employed to treat the solvent phase are described in a later paragraph. The G.C. was run with the injector chamber set at 115 C, the column oven temperature at 60 C and the filament current set at 150 ma. Column analyses were performed by an Autolab Integrator. A Leeds and Northrup strip chart recorder was used to plot the output of the integrator and to... 

The potentiometer employed was a low-resistance Type K instrument by Leeds and Northrup, with which was used a suspended coil galvanometer by the same makers. The latter was adjusted by means of a shunt until its vibrations were aperiodic, and had under these conditions a sensibility more than adequate. Care was taken before the beginning of an experiment to bring the potentiometer battery to such constancy of e. m. f. that errors from this source were negligible, and this constancy was checked at least once in the course of each series of observations by comparisons with a set of standard cells. 

Experimental. A Parr model 1221 oxygen bomb calorimeter was modified for isothermal operation and to ensure solution of nitrogen oxides (2). The space between the water jacket and the case was filled with vermiculite (exploded mica) to improve insulation. A flexible 1000-watt heater (Cenco No. 16565-3) was bent in the form of a circle to fit just within the jacket about 1 cm. above the bottom. Heater ends were soldered through the orifices left by removing the hot and cold water valves. A copper-constantan thermocouple and a precision platinum resistance thermometer (Minco model S37-2) were calibrated by comparison with a National Bureau of Standards-calibrated Leeds and Northrup model 8164 platinum resistance thermometer. The thermometer was used to sense the temperature within the calorimeter bucket the thermocouple sensed the jacket temperature. A mercury-in-glass thermoregulator (Philadelphia Scientific Glass model CE-712) was used to control the jacket temperature. 

Jacket temperature was controlled by connecting the thermoregulator and the heater to an American Instrument Co. relay model No. 4-5300. Power to the heater was supplied by a 60-cycle variable transformer normally operated at about 10 volts. Jacket temperature was recorded by feeding the thermocouple output through a Leeds and Northrup d.c. amplifier (No. 9835-B) to a Speedomax H Azar strip chart recorder. 

Calorimeter temperature was measured with a Leeds and Northrup G-l Mueller bridge used in conjunction with a d.c. Null Detector (No. 9834) or with a moving coil galvanometer (No. 2284-D) and lamp and scale. 

Gas Chromatograph. Two Wilkens Aerograph Hy-FI chromatographs equipped with electron capture detectors were used interchangeably with a Leeds and Northrup model H recorder. The recorder had a 0-1-mv. span and a W per minute chart speed. 

Emf measurements were made with a Leeds and Northrup K-5 potentiometer equipped with a Leeds and Northrup DC null detector (Model 9829). The temperature of the bath was regulated to within 0.02 K. Details of the experimental procedure, including preparation of the electrodes (19), cell design, preparation of solutions, purification of the hydrogen gas, and other experimental aspects, have been reported elsewhere (13,14). 

Instruments and Methods of Measurements. A Leeds and Northrup Type K-3 universal potentiometer, in conjunction with a General Electric Model 29 galvanometer, was used to measure electromotive force. The potentiometer was calibrated by means of a Weston Standard Cell which had been calibrated against a National Bureau of Standards (NBS) certified standard cell. Galvanic cells which were maintained at constant temperatures of 25°, 35°, and 45°C d= 0.01° by being immersed in a water bath at the desired temperature. The temperatures of the baths were set using a Fisher Scientific calibrated standard thermometer, with calibration traceable to the NBS. An adaptation of the cell sketched by Ives and Janz (II) was used. The modification of the cell was that described by Mclntrye and Amis (10). 

FIG. 20-6 Diagram of the Leeds and Northrup Ultrafine Particle Analyzer (UPA). 

Activity Software imports data from Micromeretic s Sedigraph 5100, Leeds and Northrup s Microtrac and Cilas Model 920. In operation data such as particle size distribution, surface area, filler costs or other properties are entered into the software. Target values are next assigned to the data components with the values scaled to reflect each component s... 

Leeds and Northrup Microtrac Ultrafme Particle Analyzer (VPA) uses the controlled reference method, using a sapphire tipped waveguide that collects back-scattered light within 100 pm of probe tip, to cover the size range 0.003 to 6.5 pm. 

Leeds and Northrup Microtrac Series 9200 Ultrafme Particle Analyzer Model 9230 operates in the 0.003 pm to 6 pm size range (Figure 10.19) and gives reproducible results in the concentration range 2 to 2000 ppm... 

Wertheimer, A. W. and Wilcock, W. L. (1994), Measurement of particle distributions using light scattering, Leeds and Northrup Company Advanced Technology Note 7501, 554... 

Analytical Apparatus. In the cold-trap method, mercury is detected by the gas-phase absorption of elemental mercury at 2537 A using a Coleman Instruments mercury analyzer (MAS-50) equipped with a Leeds and Northrup Speedomax recorder (model XL60I). The mercury ana-... 

B represents mean calibration by Bureau of Standards of Iron-con-stantan couples from all sources. Z represents mean calibration of Leeds and Northrup s Iron-constantan couple. 

For these studies it was desirable to maintain a constant temperature of about 22 C (room temperature). Since the amine-epoxy polymerization is an exothermic process, the syringes must have sufficient surface area to dissipate the evolved heat rapidly. Tests with Leeds and Northrup Potentiometer and a small alumel-chromel thermocouple, inserted into the center of the syringe, showed a maximum temperature rise of less than 2 C during the entire reaction time. This was sufficiently small to assume that isothermal conditions were maintained. 

Recorder, with millivolt range(s) compatible with the AA spectrometer and with a similar 0.5-sec response time. A Jarrell-Ash model 82-500 AA spectrometer and a Leeds and Northrup Speedomax W 10 mV recorder were used in the development of this method. 

One of the first precise vacuum or inert-atmosphere instruments was designed and constructed by Whitehead and Breger (37). The furnace was constructed from an alundum core, 9 in. in length by 2 in. ID, wound with Chromel A resistance wire. The core was shielded by four sheet-nickel cylinders, mounted on three posts, and the entire assembly was placed inside a 12 x 24-in. Pyrex bell jar. All electrical connections were made through the bottom of the bell jar mounting base. The sample block was made in the dimensions shown from Type 446 or 309 stainless steel. The furnace heating rate was controlled by a Leeds and Northrup Micromax controller the differential temperatures were recorded on a Beckman Photocell recorder. 

With the controlled atmosphere heated sample holder, it was a simple matter to connect a thermistor-type thermal conductivity cell to the system and, by means of an external multichannel recorder, record the DRS and the evolved gas detection lEGD) curves simultaneously (17). This modification of the apparatus is shown in Figure 9.4. The cell was connected to a Carle Model 1000 Micro-Detector system by means of metal and rubber tubing. The thermal conductivity cell was enclosed by an aluminum block which was heated to 100 C bv means of a cartridge heater. The block was connected to a preheat chamber, also operated at 100 C, which was used to preheat the helium gas stream before it entered the detector. The output from the detector bridge was led into one channel of a four-channel 0-5 mV Leeds and Northrup multipoint strip-chart potentiometric recorder. The temperature programmer from a Deltatherm III DTA instrument was used to control the temperature rise of the DRS cell. Output from the Beckman Model DK-2A... 

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