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PROGRAMMING THE A/B, (A-B)/B, AND A-B DISPLAY C MODES

This section will deal with the programming and operation of the Gemini 5200

in the modes which include Display C, [41 2,3,4]. Since all three display C modes
are very similar in operation, they will all be covered in one section.

BASIC OPERATION

In all of the display C modes, the Gemini 5200 performs a mathematical

calculation using Rate channels A & B to obtain the Display C value.

The two rate indicators, use a time interval method (1/tau) to calculate the rate

value. This method enables high resolution at all input rates. The unit counts
input pulses and after a programmable minimum update time has occurred, it
waits until the next count edge occurs, takes the elapsed time and number of
edges, and calculates the rate value. At slower rates, averaging can be
accomplished by programming the “Minimum Update Time” (0.5 sec. to 16 sec.)
for the desired response.

When operating in any of the three modes which utilize display C, the two rate

indicators will synchronize themselves in order to obtain an accurate display C
reading. The Gemini 5200 will determine which channel is running at the slower
rate, and it will use that channel to synchronize the other channel. This is done so
that both time measurement windows are as close as possible. Because it is
necessary to keep the measurement windows the same, there is only one Rate
Minimum Update Time setting. The slower channel will determine the update
time for the other rate channel and Display C.

If one rate input signal drops out before the update period has completed, that

channel will go to zero after the maximum update time has expired. The channel
will then continually time-out according to the maximum update time that was
selected in Code 63, until a rate signal again appears on its input. After the first
time-out, the other channel, which still has a rate signal on its input, will then
begin to operate in a non-synchronous manner, updating according to the
“Minimum Update Time” and its input frequency. It will not synchronize with
the channel that timed-out, and has an update period of 16 seconds.

The Display C channel, however, will only update according to the

maximum update time because it is calculated based on both of the rate
channels. The rate channels will again synchronize when both channels have a
rate signal on their inputs.

CODE 41 - UNIT PERSONALITY

The unit personality mode is the first function code that is programmed. This

mode will determine the basic operational characteristics of the unit. This
programming section deals with the unit personality programmed as a Dual Rate
Indicator with Display C, modes 2, 3, or 4. A separate section, “Programming
The Gemini 5200 In Dual Rate Without Display C Mode” goes over the
programming of the Gemini 5200 when programmed in mode 1.

Whenever the Unit Personality mode is changed, the factory settings will

automatically be loaded into the unit’s memory. This provides a known starting
place. If at any point, it is desired to return to the factory settings for the current
personality, the unit personality is called up, a minus is put in front of the mode by
pressing the “+/-” key, and the “E” key is pushed to load the factory settings.

[41 1] DUAL RATE INDICATION - In this Unit Personality, the Gemini 5200

operates as two independent rate indicators. See “Programming The Gemini
5200 In Dual Rate Without Display C Mode” section for programming details.

[41 2] DUAL RATE WITH A/B DISPLAY C - In this unit personality, the

Gemini 5200 operates as a dual rate indicator with an A/B (Speed Ratio)
Display C function.

[41 3] DUAL RATE WITH A-B DISPLAY C - In this unit personality, the

Gemini 5200 operates as a dual rate indicator with an A-B (Speed Difference)
Display C function.

[41 4] DUAL RATE WITH (A-B)/B DISPLAY C - In this unit personality, the

Gemini 5200 operates as a dual rate indicator with an (A-B)/B (Speed Draw)
Display C function.

[41 -1]
[41 -2]

A minus indicator preceding the mode will cause

[41 -3]

the factory settings to be loaded when entered.