REPORT
the input signal (and hence the output which drives the motor) is reduced to zero. This is the principle of the servomechanism, which is now so widely used in chemical instrumentation. The Cathode Follower. In voltage amplification, an input signal on the grid of the amplifier first stage is converted into a larger signal appearing across the load resistor, RL, in the plate circuit. As Figure 6,A, shows, the voltage amplification increases as this load resistance increases. However, when RL is very large, the tube current (and, hence, the load current) is small, and the ability of the current to deliver power to the load (P = PRL) is ever smaller. Figure 6,B, shows that the maximum output power is obtained from an amplifier when the internal resistance of the latter, rv, is equal to the resistance of the load, RL- Thus, in power amplification it is important to match the impedance of the source of a signal to that of the load that is to be energized. In many chemical problems the signal source has a very high internal impedance, and it is necessary to employ special impedance matching circuitry in order to couple this
NEW TABLE-TOP SIZE
HYDROGEN PURIFIER . produces 99.999 + % pure and dry hydrogen from impure sources
If your requirements involve ultra-pure, dry hydrogen, here's a versatile, small capacity purifier a t a very economical price. With practically instantaneous warm up, this unit produces 99.999 + % pure hydrogen for either laboratory studies or process control chromatography. Two table-top size models are available . . . Model CL-A with a capacity of 40 ml/min for laboratory studies and Model CH-A with a rated capacity of 100 ml/min for process control. These units are specifically designed for gas chromatography, flame photometry, hydrogen work, or wherever high purity hydrogen is required, instantly and economically, in small quantities.
Employs palladium-silver alloy for diffusion Source gas with 7 5 % or more hydrogen*, such as cylinder hydrogen or dissociated ammonia is passed through a special palladium-silver alloy t h a t selectively separates hydrogen from all impurities. Result is hydrogen so pure that modern analytical techniques cannot detect impurities. And, the palladium alloy never becomes brittle, needs no purging.
A.
Pure hydrogen—at the flip of a switch
B.
The unit is simply plugged into any convenient 115-volt, a-c outlet, the impure hydrogen connected to the inlet...pressure and flow adjusted to the proper operating range and the ultra-pure, dry hydrogen collected a t the outlet.
. . . and economical, too
C
The Model CL-A, 40 ml/min capacity, and the Model CH-A with a 100 ml/min rating are economical initially and cost little to operate. Delivery approximately 30 days. *Capacity proportionate to hydrogen content in source gas. Rated capacity based on 98'
D.
EJL
cx
Figure 10. Operational amplifier circuits. In each case the output voltage is related to the input function by the following operation: A. multiplication by a constant; B. summation of the individual inputs; C. integration; D. differentiation
H,
Bulletin No. 1159-1 describes in detail the entire line of Milton Roy Hydrogen Purifiers—including standard units up to 200 cfh capacity.
Controlled Volume Pumps Colorimetric Analyzers Hydrogen Purifiers Laboratory Instruments
Write for Bulletin #1159-1. Milton Roy Company, 1300 E. Mermaid Lane, Philadelphia 18, Pa.
Circle No. 168 on Readers' Service Card
VOL. 34, NO. 2, FEBRUARY 1962
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