Measuring Circuit - TM-11-6660-204-250013

TM 11-6660-204-25

operate the recording portion of the equipment.

g. Frequency-Time Recorder. The frequency-

The phase of the error voltage referred to the

time recorder is an electromechanical device

powerline phase is dependent on the polarity of

which in effect makes a continuous printed record

of the pulse recurrence frequency of the signals

the unbalance between the two dc voltages.

received from the radiosonde receiver. The chart

d. Measuring Circuit.. The measuring circuit

motor continually advances the chart under the

contained in the control panel consists of an ar-

recorder pen at the rate of l/2-inch per minute (1/2

rangement of resistors and potentiometers to de-

or 1 inch per minute in Frequency-Time Record-

velop and control the voltage across the slide-wire

ers RD88A/TMQ5 and RD-88B/TMQ5, and

potentiometer which is mounted on the frequen-

1, or 2 inches per minute in Frequency-Time

cy-time recorder chassis. A test voltage is also

Recorders RD-88C/TMQ-5, so the received data

developed in the measuring circuit and is used to

are spaced along the chart from the beginning to

check the operation of the recorder.

the end of each radiosonde flight.

e. Servoamplifier. The servoamplifier system

h. Power Supply. The power supply contains

consists of five voltage amplifiers and a line volt-

circuits that supply the voltages used to operate

age compensating tube in the converter-amplifier

the recorder and its associated circuits. It com-

chassis, together with two power amplifier tubes

prises one common power transformer which fur-

located in the power supply. The 60-cycle error

nishes an unregulated voltage for the balancing

voltage from the detector is amplified in these

motor circuit, a positive supply voltage, and a

stages, and is then used to drive the balancing

negative supply voltage together with regulator

motor in the frequency-time recorder chassis and

circuits to maintain these dc voltages at a steady

to actuate the pen-lifting circuit in the power sup-

potential. Power supply also contains the servo-

ply chassis. The pen-lifter circuit operates a sole-

power amplifier tubes, the pen-lifter circuit and

noid which is mechanically coupled to the pen car-

tubes, and the solenoid relay.

riage of the recorder. When power is applied to

i. Functional Operation. In considering the

the solenoid, the pen is lowered onto the chart. It

is raised from the chart whenever an error volt-

functioning of the recorder throughout the follow-

age exists, so the chart is not marked while the

ing detailed circuit analysis, bear in mind that

pen is being moved to the proper position.

basically the signal converter contains the wave

shaping and pulse forming circuits for the detec-

f. Balancing Motor B501. The balancing motor

tor. The servoarnplifier system contains the volt-

is a two-phase motor which is mechanically cou-

age amplifiers, power amplifiers, and pen-lifting

pled to the moving arm of the slide-wire poten-

and operating circuits, which are associated with

tiometer asd to the recording pen. One winding of

the balancing motor circuit in the frequency-time

the motor is connected to a 60-cycle excitation

recorder. The control panel supplies controls for

voltage, and the other (control ) winding is con-

the measuring circuits and the adjustments for

nected to the output of the servoamplifier circuit.

proper operation, and the power supply furnishes

When the balancing motor is actuated by the

the necessary operating potentials, The received

error voltage generated in the detector circuit, it

drives the slide-wire potentiometer contact arm.

radiosonde signals, regardless of their wave shape

The slide-wire contact arm voltage changes as the

and amplitude at the recorder input, are con-

balancing motor continues to revolve. When this

verted into a dc voltage which is proportional to

voltage becomes equal to the signal voltage ap-

the low recurrence frequency of the input signal

plied to the detector, the error voltage is canceled

at any instant, This dc voltage is then applied to

by the balanced-bridge condition, and the balanc-

an electromechanical recorder which translates it

ing motor stops. While the balancing motor ro-

tates the pen-lifter mechanism holds the pen

and marks off the frequency variations corre-

above the chart, the pen moves across the chart;

sponding to temperature and relative humidity

the pen makes no mark because it is in a lifted

readings as transmitted by the radiosonde. The

position. The sequence of operation is such that

chart can be read directly by a skilled operator or

the pen always marks the chart at a point that

used at a later date for further evaluation of each

corresponds to the meteorological information

radiosonde flight.

being received.

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