TIMING CONTROL METHODS AVAILABLE 
FOR SELF-CONTAINED RECORDING SYSTEMS 
by ALEXANDER L.M. DINGEE, Jr., and A. FRED FEYLING 
Geodyne Corporation 
Waltham, Massachusetts 
ABSTRACT 
Timing methods are important in data col- 
lection. There are a large variety of direct 
current powered timing devices which might be 
used in self-contained data recording or trans- 
mitting devices. This paper discusses accuracy, 
price and some of the significant aspects of 
various timing devices which can be used in 
oceanographic and limnological equipment. 
INTRODUCTION 
In recording oceanographic and limnological 
data, the time axis is often as important as the 
variables being recorded. Recording or con- 
trolling with respect to time can be difficult 
without 60 cycle A.C. power available. For ex- 
ample, in self-contained recording or telemetry 
buoys, using lapse-time techniques to store or 
transmit information, the simple closure of a 
switch on cycle presents significant problems 
which can easily be solved in the laboratory 
with a $1.98 clock motor. 
Oceanopraphers are not the only group faced 
with this problem. Lincoln Laboratories, at 
M.1I.T., received an ionospheric sounder to 
measure the time it takes a radar pulse to travel 
to the ionosphere and return. These units were 
used throughout the world for the International 
Geophysical Year. The equipment also required 
a switch closure once every fifteen minutes to 
control a film advance mechanism. Two large 
crates were delivered to Lincoln Laboratory. The 
first contained a six-foot rack of sophisticated 
space-age electronics for measuring the radar re- 
flectance time. This was the ionospheric sounder 
unit. The second crate, larger than the first, 
contained the time standard for the film re- 
corder, complete with proper cams and micro 
switches. It stood over 6' tall in the original 
beautiful mahogony case. This timing unit, sup- 
plied by a well-known space-age company, was a 
good, reliable grandfather's clock. 
In this study of small, self-contained D.C. 
powered timing sources capable of low frequency 
switching, cycles of one minute to twelve hours 
were covered. Other considerations were: tem- 
perature range, dependability, size, weight, 
power consumption and ease of maintenance and ad- 
justment. Repeatability, accuracy ran from 
77 
1 part in 10° to 1 part in 5. For practical pur- 
poses we eliminated atomic resonance for we felt 
that most oceanographers would not want to pay 
between $10,000 and $100,000 for accuracies of 
one-ten millionth of a second per day. 
DISCUSSION OF TIMERS 
Points to be considered with electronic 
timers are the effect of voltage variation, tem- 
perature variation, moisture and aging of parts. 
Generally electronic timers operate at high fre- 
quencies and require preset counting circuits to 
trigger switches. The contact closure is usually 
controlled magnetically or vy solid-state relay. 
Types of timers are as follows: 
. A crystal 
which can operate at frequencies as low as 1 kilo- 
cycle can easily obtain accuracy of +1/10 of a 
second per day. The use of counting circuits is 
necessary to count down to the desired number of 
pulses per hour. Due to this counting the price 
of such a unit wil] run from approximately $500 
to $2,000. 
Tuning Fork Oscillator. This is much the same 
as a crystal oscillator except that a tuning fork 
is used for the frequency source. Such a unit may 
operate as low as 50 cycles per second. The 
accuracy is 410 seconds per day. The counting 
circuit is simplified because the base frequency 
is lower. Cost of such a unit would be $350 to 
$1,600. 
L.C. Resonant Circuit. Proper combination of 
inductance and capacitance will give a circuit 
which will oscillate at a given frequency. Ac- 
curacy can be better than +1 minute per day. An 
L. C. circuit can be made to operate as low as 
5 or 10 cycles per second. A counting circuit 
for switch closure is still required. The approx- 
imate price would be $200 to $500. 
Relaxation Oscillator using resistive and 
capacitive or inductive circuitry. An example is 
the charging of a capacitor with a2 battery to a 
given voltage level at which point a neon bulo, or 
other detector, triggers and discharges the capa- 
citor. The cycle time is limited by the size and 
leakage from the capacitor. It is fairly easy to 
