4-30 Manual # 42-02-2223
Final Adjustment
Load Weigher Adjustment for Dispatching
Analog load weighers (isolated platform or crosshead deflection) provide a signal (analog volt-
age) corresponding to measured load. The signal is conditioned and digitized by the control sys-
tem. The resulting value is used to calculate actual load inside the elevator, which is used for
logical operations including:
• Overloaded car detection
• Heavy load (hall call bypass)
•Light load anti-nuisance
• Empty load detection
Each threshold is user-programmable (Load Weigher Configuration screen) to determine the
load level at which each operation should be initiated.
The car is weighed only when it is stopped at a landing with doors open. If the car were weighed
when running, acceleration and deceleration would be interpreted as weight change.
Rope Tension Load Weigher - Load cells sense the tension of the wire ropes. The load
weigher provides a calibrated analog signal that accurately tracks the loading of the car. Due to
the dynamics of the elevator system, the load represented by the traveling cable and compensa-
tion cables will vary with the position of the car in the hoistway. iControl must learn the empty
and full car load value at each floor. The load in the car can then be determined by reading the
value at a given floor and subtracting the learned empty value for that floor.
Crosshead Deflection Load Weigher - The signal generated by the load sensor represents
the perceived load at the crosshead, which includes the weight of the car, the load inside the
car, the traveling cable, and any compensation cables that might be attached to the car. Due to
the dynamics of the elevator system, the load represented by the traveling cable and compensa-
tion cables will vary with the position of the car in the hoistway. iControl must learn the empty
and full car load value at each floor. The load in the car can then be determined by reading the
value at a given floor and subtracting the learned empty value for that floor.
Isolated Platform Load Weigher - The isolated platform load weigher measures only the
weight within the car. The value is not affected by hoistway position so empty and full values
can be learned without moving the car from floor to floor.
Note: If you are preparing to do safety testing, including governor and buffer tests, you might
want to do them first, then adjust the load weigher because re-calibrating the load weigher is
recommended following buffer safety tests.
Load Thresholds The load thresholds used in logical operations are:
• Over load threshold (% of full load): Used to define the load at which it is unsafe to
move the elevator (iView Configuration > Load Weigher tab). If this threshold is exceeded,
the car will remain at the floor with doors open. Typically some type of visual and/or audi-
ble indicator is used to alert passengers that the car is overloaded. (This operation is over-
ridden during Fire Service operation.)
• Heavy load threshold (% of full load): Used to define the load value at which hall
calls will be bypassed or reassigned (iView Configuration > Load Weigher tab).
• Light load threshold (% of full load): Used to define the load at which a limited num-
ber of car calls may be registered. If the programmed number of car calls is exceeded, all
car calls will be canceled.
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