From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Leaflet for the Cossor-Dodds Amplifier Model 3352.
| Identifier | ExFiles\Box 167\2\ img251 | |
| Date | 12th February 1940 guessed | |
| COSSOR INSTRUMENTS COSSOR-DODDS AMPLIFIER Model 3352 DESIGNED FOR PRESSURE RECORDING WITH CONDENSER TYPE PRESSURE UNIT. PRICE £25. DESCRIPTION This Amplifier is primarily intended for use with the Model 3361 Cossor-Dodds Condenser Pressure Element. It forms an essential part of any pressure or movement measuring equipment using the variable capacity type of element. With the 3361 type element it will measure cyclic pressures from a few pounds per square inch up to several thousand pounds per square inch by using elements fitted with diaphragms of suitable thickness. It will operate on any variable capacity device for the measurement of displacement directly, or of stress or pressure indirectly. In addition to measuring displacement or pressure, it can also be used to measure "velocity" or rate of change of pressure and incorporates suitable switching for this purpose. The output from this amplifier is of the order of two or three volts, and must be further amplified before being applied to a Cathode Ray Tube. If a High Vacuum type Tube Unit such as the Model 3313 is to be used, a Model 3355 Amplifier is required to give balanced or symmetrical operation. If a Gas Focussed type Tube is to be used, such as in the Model 3345 Gas Tube Unit, a Model 3396 Combined Amplifier and Time Base, or, in certain cases, the Model 3371 Amplifier should be used. Reference should be made to the separate leaflets describing these instruments for complete particulars of their performance. The complete equipment has been designed primarily for engine indicating work on internal combustion or other engines, covering a speed range from about 150 R.P.M. up to the highest speeds obtainable. The lower limit is set by the time constants of the couplings in the Amplifier and accurate results cannot be obtained much below the speed given. The upper limit is not imposed by the Cathode Ray Oscillograph or associated Amplifiers whose performance may be relied upon up to frequencies of the order of 20,000 c.p.s. There is, therefore, adequate margin in all engine indicating problems, including detonation in supercharged aircraft engines. The circuit comprises a 2-stage valve amplifier which is preceded by the necessary polarising and input circuits to the condenser element. The two 120 volt H.T. batteries, required for the anode supply of the valves and the polarising potential of the pressure element respectively, are contained in the case. Five different polarising voltages are obtainable by means of the GAIN control. The grid circuit consists of two arrangements, the first when measuring pressure of displacement, consisting of a shunt condenser and a parallel resistance, and the second consisting of four alternative resistances. The former circuit, the integrator, gives either pressure or displacement and the latter gives four sensitivity positions for the rate of change of pressure or "velocity". The Amplifier comprises a 41MTL Triode followed by a Cossor MS/Pen screened Pentode, both inductively compensated resistance-capacity stages of long time constant, covering a range from 2 to 50,000 c.p.s. The filament supply is obtained from an external 4 volt accumulator which should be of adequate capacity to avoid slow drifts and changes in sensitivity. COSSOR INSTRUMENTS Leaflet No. CI.289 | ||