ZF CruiseCommand 785CE, Installation And Troubleshooting Manual

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TROUBLESHOOTING TRAIN-156 Rev.B 11/01
Page 19
• The Transfer Button must be depressed which takes the “Station
Select” signal from 5.00 VDC to 0.00 VDC.
These items can be tested as follows:
1.6.1 Command Signal
As mentioned previously, the Command Signal is a DC voltage which
varies in relationship to the Control Head’s lever position. The Proces-
sor provides each Control Head 5.00 VDC, which is referred to as the
“Reference Voltage”. The Reference Voltage is applied to a 5K Potenti-
ometer in the Control Head. The potentiometer’s “Wiper” taps off a por-
tion of the Reference Voltage and sends it back to the Processor. The
amount of DC voltage which is tapped off, is dependant on the position
of the Control Head’s lever. When the lever is fully Astern, a small por-
tion of the Reference Voltage is tapped off by the wiper, and therefore,
the voltage is at its lowest point (approx. 0.60 VDC). When the lever is
positioned fully Ahead, a larger portion is tapped off and the voltage is at
its highest point (approx. 4.40 VDC).
Since all the calculations within the CruiseCommand system are per-
formed digitally, these DC voltages are expressed as and converted to a
digital representation. The “Reference Voltage” (approx. 5.00 VDC) by
which all analog inputs are based, is represented as 1023 A/D (Analog to
Digital) Counts. This allows for the possibility of a 1024 possible posi-
tions when 0 is included in the count. The value of the Command Volt-
age, with the lever at the Neutral/Idle position is 48- 50% of the
Reference Voltage or 491- 511 A/D’s (2.40- 2.50 VDC). The Command
Voltage at Full Ahead is 83- 85% or 849- 869 A/D’s (4.15- 4.25 VDC)
and Full Astern is 12- 14% or 123- 143 A/D’s (0.60- 0.70 VDC).
Since the Commanded Signal is based on a percentage of the Reference
Voltage, the distance of the Control Head from the Processor has no
impact on the performance of the system. The amount of voltage drop,
due to current flow, is the same for both the Reference and Command
Voltages. The relationship between the Reference and Command Volt-
ages when thought of as a percentage, will remain the same regardless of
distance. For instance, here are two examples.
Example # 1 Example # 2
Reference Voltage 5.00 VDC 1023 A/D Counts Reference Voltage 4.80 VDC 1023 A/D Counts
Command Voltage
2.45 VDC 501 A/D Counts
Command Voltage
2.35 VDC 501 A/D Counts