Patent GB-627030-A (GB)
Title: Improvements in recording and controlling apparatus
IPC: G08C13/02
Filed: 1946-09-18
Abstract: 627,030. Potentiometers. BENDIX AVIATION CORPORATION. Sept. 18, 1946, No. 28062. Convention date, Oct. 4, 1945. [Class 37] [Also in Groups XXXV and XXXVIII] In a system controlling a physical-condition in response to. the average of a plurality of observations of the condition, test stations are cyclically and segmentally switched successively to operate a metering device which develops a pulse, displaced in time from the incidence of operation by an interval dependent on the magnitude of the condition tested. A summing device is started by the segmental station switch at each test, and is stopped by the time displaced metering pulse, the results being cumulatively summed for a predetermined number of tests, when the total operates a control switch regulating the condition, under test, and the summing device is zeroised. The control switch position at the end of a test cycle is maintained until it is reset on completion of the following test cycle. The values of the controlling condition and of another measured condition are successively recorded by printing drums for each test station, with the station number and time of observation. Fig. 1 shows a temperature and humidity test station wherein a temperature sensitive resistance 38 and a fixed resistance 36 are connected as a potentiometer to produce a temperature responsive alternating voltage across terminal 42-44 from the A.C. supply across terminals 42-40 derived from transformer 546. A humidity sensitive tensioned hair element 46 moves a pointer 50 in proximity to an A.C. fed resistance 54 and is periodically urged into contact therewith by a bar 56 operated by the D.C. energization of coil 58 from terminals 42-64 to produce a humidity responsive alternating voltage across terminals 62-42. A plurality of such test stations 20, 22, 24, 26, 28, 30, 32, 34 are distributed in the controlled enclosure and are respectively connected, Fig. 2, to the moving contacts of spring sets 68, 72, 74, 76, 78, 80, 82, 70 of a selector assembly 66, the fixed contacts of which are paralleled by conductor 138 so that each test station is sequentially connected to the recording and controlling apparatus, Figs. 2, 3, by the operation of the 120 degree spaced arms 100, 102, 104, which are stepped clockwise by a ratchet and pawl operated by cam 162 once per revolution of shaft 168, also' carrying cams 182, 184, 186, 188, 190, rotated by A.C. motor 170 through reduction gear 172, and geared to rotate shaft 218, at twice the speed of shaft 168, together with the printing drums 222, 224 and the sliders of sweep potentiometers 206, 212 which are supplied with A.C. from transformer 546. On closure of main switch 178, the system is as shown, station 20 is selected and the ganged switches 144, 196, 198 are positioned by cam 190 for humidity measurement. An alternating voltage indicating the humidity at station 20 is supplied to transformer 424 through switch 144 and calibrating switch 416, and an alternating, humidity sweep voltage from potentiometer 212 is supplied to transformer 430 through switch 196. The transformer outputs are rectified by diodes 442, 436, the resultant direct voltages being applied to the grids of balanced triodes 450, 460 which feed the control windings of saturable reactors 456, 466. The A.C. windings of the latter are connected in a balanced circuit with the secondary of supply transformer 494 so that unbalance currents energize winding 496 of 2-phase drag-cup motor 498, to move contact arm 506 between abutment 508 and contact 510. Initially the sweep voltage is greater than the humidity indicating voltage so that the contact arm lies on the abutment until the humidity voltage first balances and then exceeds the sweep voltage, when the contact arm moves over to the contact, triggering the gasfilled tetrode 524 to operate relay 260 to energize the latch release coil 320 of relay 286, thus arresting the summation motor 294 which was started by the closure of switch 280 by cam 184 to operate and latch relay 286 on commencement of the measurement cycle. Thus summation cam 302 is rotated against spring loading by an amount dependent on the magnitude of the humidity signal voltage and is then held in position by brake 314. Timing motor 232 drives time printing drum 230, and cam 236 operating a time switch 272 at fixed intervals to energize the humidity tapper coil 248 through switch 198 causing tapper bar 244 to print on strip chart 276 the time of record, and the humidity value derived from the printing drum 224 rotated together with the slider of the humidity sweep potentiometer 212. When the slider has reached the end of its travel, shaft 168 has rotated sufficiently for cam 182 to open switch 374 to insert a resistance in series with relay 260 to prevent operation until the slider has again returned to the beginning of its travel. After shaft 168 has rotated half a revolution from the commencement of the measurement cycle, cam 190 re-positions the switches 144, 196, 198 for temperature measurement, and the voltage across resistance 38 in station 20 is applied to transformer 424 and the voltage from the slider of the temperature sweep potentiometer 206 is applied to transformer 430. The steadily increasing sweep voltage becomes equal to the temperature indicating voltage, when contact arm 506 moves from abutment 508 to contact 510, energizing relay 260 to operate tapper bar 238 to print a record of temperature from printing drum 222 and the test station number from printing wheel 226 rotating with the movement of the ratchet and actuator arms of the selector assembly. After one complete rotation of shaft 168, the actuator arms are moved clockwise by one ratchet notch, test station 20 is switched out and test station 22 is switched in to the recording and controlling apparatus to record humidity, time, temperature, and station number as before, and the same process is repeated for stations 24, 26, 28, 30, 32, 34, until when test station 34 is switched to the recording and controlling apparatus, cam 157 rotated by the ratchet wheel closes recycle switch 161 so that, after the humidity has been measured, switch 324 is closed by cam 186, control latch relay 337 is energized to operate or release in dependence on the position of switch 340 which in turn depends on the degree of rotation of the summation cam 302, which is proportional to the sum of the humidity indications at the test stations. On further rotation of shaft 168, cam 186 opens switch 324 and cam 188 closes switch 326, energizing coil 330 through switch 161 to release the brake 314, allowing the summation shaft to return to its initial position, while the operated or released condition of the control latch relay 337 is retained until over-ridden by the result of a subsequent averaging of humidity readings, and the relay contacts control the operation of a humidity correcting motor or load 358 at 15 minute intervals. Series variable resistances 576 and 580, and voltage control resistances 570 and 572 enable the scale distribution of the printing elements to be adjusted in conformity with fixed voltages derived from calibration switch 416. Specification 630,690 is referred to.