412 Alex Goodman 
input impedance, and therefore negligible loading effect on transducer initiating signals, 
drift of less than 2 microvolts per 10°F change in ambient temperature for the 0.1- to 30- 
inillivolt input ranges, and for frequencies of 0 to 10 cycles per second, an equivalent input 
noise of about 4 microvolts peak to peak. This amplifier, the Accudata III, is manufactured 
by Minneapolis-Honeywell Company. Seven of these amplifiers are used in the system; one 
for each gage. 
The multiganged sine-cosine potentiometer (eight potentiometers mounted on one shaft) 
is mechanically attached to the Planar Motion Mechanism driveshaft in the same manner as 
that used for synchronous switch, shown in Fig. 14, and rotates at the displacement fre- 
quency w. Each sine-cosine potentiometer has a function conformity of +0.25 percent from 
0 to 360 degrees. These potentiometers are manufactured by the Beckman Heliopot Company. 
The output of the signal amplifier is applied to the input of the sine-cosine potentiome- 
ter within the circuitry of the force component separator. The force component separator 
consists of seven channels, one for each gage. The major components of the force compo- 
nent separator unit are the function switch, normal-reverse switch, and function relays. 
The function switch has four settings which are identified as quadrature, reset, in-phase, 
and calibrate. The quadrature position electrically multiplies the amplified signal from each 
signal amplifier with the cos wt generated by a corresponding cosine wiper of the sine- 
cosine potentiometers. The in-phase position performs a similar multiplication with sin ot. 
In the reset position, the feedback capacitor of the integrating amplifier is shorted out and 
the output. voltage of the integrating amplifier is returned to its zero level. In the calibrate 
position, the sine-cosine wipers are disconnected and the signal is multiplied by unity in- 
stead of either sin wt or cos wt. The significance of this will be discussed later. The 
normal-reverse switch changes the polarity of the signal feeding into the sine-cosine poten- 
tiometer. This feature eliminates the requirement for knowing the static zero precisely; that 
is, it eliminates the need for having the transducer balanced exactly. 
The product of the signal with either the sin wt or cos wt is fed into the integrating am- 
plifier. This amplifier is another Accudata III operated in the open-loop mode and having a 
precision capacitor in the feedback loop. Again, one integrator is used for each gage in the 
system. The feedback capacitor has a value of 0.5 microfarad (accurate to within +0.1 per- 
cent) and is manufactured by Arco Electronics Company. The output voltage of the integrat- 
ing amplifier is fed through the contacts of the function relays; identified as “integrate” 
and “hold.” These relays are controlled by a precision stepping switch located in the in- 
tegrate timer unit. The operation of the stepping switch is controlled by a microswitch 
which is actuated by a sweeper mounted on the drive shaft. The number of pulses to be 
counted, corresponding to revolutions of the drive shaft, can be selected by a switch located 
on the integrate-timer unit. The home position of the stepping switch and function relays 
corresponds to the reset position mentioned previously. Upon being pulsed, the stepping 
switch operates the integrate and hold relays and then rotates an amount corresponding to 
the selected number of cycles. At this point the integrate relay is deenergized, opening the 
input to the integrating amplifier. At the same time the hold relay maintains the charge on 
the feedback capacitor of the integrator. The integral of the signal is therefore, the output 
voltage of the integrating amplifier divided by the selected time of integration. This voltage 
can be recorded and read out by either the digital servo system or Brown recorder. 
The operation performed by this system is equivalent to determining the Fourier coef- 
ficients of the fundamental of the gage signal [10,11], as illustrated in Appendix C. 
