Input Amplifier (Dwg. #0102-5000-03)

4.2.3

(Cont'd)

The Totalizer unit is a multistage decade counter with display. The proper signal, after having been

processed by the Logic unit, is counted in the Totalizer. The Totalizer merely accepts the pulses from

the Logic unit, converts them to decimal format where they are displayed in the glow discharge readout

tubes and presented to external printers, etc. in proper format.

Other items shown on the Chassis Interconnection Diagram are the Power Supply, Transformer and

external connection points. The Power Supply provides the regulated +5 V necessary for all IC and

transistor circuitry used throughout the counter.

Also supplied is +180 V peak that is used by the glow discharge display tubes. Each of these supply

potentials may be easily monitored throughout the system as shown on the diagram. A separate drawing

of the transformer #0103-5005-04 is located in Section 4.4 and shows terminal connections for 115 V

operation or 230 V operation. Conversion from one voltage source to another is accomplished merely by

setting S17 to the proper position and reducing the fuse by one-half.

4.2.4

Input Amplifier (Dwg. #0102-5000-03)

The Input Amplifier consists of a field effect transistor input stage Q1 coupled to the linear amplifier

stage. The amplifier includes a low pass filter between these stages to eliminate high frequency noise.

This unit has been designed to begin its 12 db per octave roll-off characteristic at approximately 5 KHz.

This is followed by a linear gain stage Q2 driving a DC coupled saturating switch. The switching stages

Q3 and Q4 are set for a high threshold, thereby greatly reducing sensitivity to noise. In the quiescent

state, Q4 is conducting and Q3 is off. The final stage Q5 is used to provide an inverted output where

required.

The Input Amplifier features high sensitivity with limited bandwidth. It is intended for use with low level

output devices such as tachometer, turbine flowmeters and other electromagnetic sensors. The upper

frequency limit is deliberately rolled off to minimize noise pickup from unwanted signals. Because input

sensitivity above 5 KHz is reduced at a rate of 12 db per octave, the effects of high frequency electrical

noise transients generated externally by solenoids and other combinations of inductors and switches are

greatly minimized. Check The Specifications, Section 1.1 for maximum amplitude signals allowable with

the various settings of the Input Multiplier.

4-15