Patent GB-538160-A (GB)
Title: Improvements in or relating to electrical integrating apparatus
IPC: G01J1/42
Filed: 1939-12-13
Abstract: 538,160. Quantity meters. SANGAMO WESTON, Ltd. Dec. 13, 1939, No. 32158. Convention date, July 15, 1939. [Class 37] An integrating photometer comprises a coil mounted for oscillation in a magnetic field, switching means for reversing the current in the coil in its limit positions, a barrier-layer type photo-electric cell adapted to feed current to or control the supply of current to the winding, and counting means for registering the number of oscillations of the coil. A coil 1, Fig. 1, is wound on a metal frame 2 and is supported in bearings for pivotal movement in the gaps between the polar surfaces of a permanent magnet 3 and core 4. The coil carries a contact arm 5 moving between stationary contacts 6, 7 that limit the oscillatory motion of the coil. The moving coil 1 is connected to the blades of a polarityreversing switch 10 to which a photocell 11 of the barrier-layer type is connected. The blades of the switch 10 are operated in one direction against a restoring spring by a coil 12. The engagement of the arm 5 with the contacts 6, 7 controls a pair of interlocking relays 14, 15, which in turn control the energization of a counter 16 and the polarity-reversing switch 10. The distance apart of the contacts 6, 7 is adjustable to determine the angle of oscillation of the coil 1. In a modification, Fig. 3, for operating from A.C. mains, a step-down transformer 26 and a rectifier bridge 27 supply direct current to leads 20, 21 for actuating the relays. A polarized relay 28 has a contact arm 51 which is normally held against a contact 6<1> and is moved to engage a contact 7<1> when the arm 5 engages the contact 7. The relays 14a, 15a have each a set of contacts b for interlocking and a double set of contacts d for reversing the polarity of the photocell current supplied to the coil 1. By means of a manually operated switch 32 the polarity of the input from the photocell 11 may either be such that the polarity reversals at the relay contacts d maintain the oscillating travel of the coil 1 as its contact arm engages the contacts 6, 7, or such that the coil 1 is stalled with its contact arm 5 against one of the contacts. The counter 36 is operated through a sensitive polarized voltage relay 34 and a power relay 35. The counter 36 has a set of numeral wheels 38, on which the counting is registered, a second set of numeral wheels 39 which may be adjusted manually to a desired value, and a switch 40 which is closed when the value registered on the wheels 38 reaches the value set on the wheels 39. The switch 40 controls the energization of an alarm or shutter operating mechanism 41. The mixing coil 1 moves at an angular velocity such that the torque due to the current through the coil is equal to the reaction torque of the induced current in the metal coil frame 2. The direction of travel of the coil 1 is reversed by the relays 14, 15 as the contact arm 5 strikes the contacts 6, 7, the total travel of the coil being registered in terms of cycles of oscillatory travel. This is a measure of the integrated light values, and the apparatus may be adjusted to read directly in foot-candle-seconds. In a modification, the rate of displacement of the coil 1 is determined by a resistance in parallel therewith, instead of by a metal frame. The coil moves with a velocity such that its induced E.M.F. is equal to the voltage drop across the shunt resistance due to the cell current.