Monitor alarm can prevent expensive weighing errors

2nd April 2014
Source: Aptifirst
Posted By : Nat Bowers
Monitor alarm can prevent expensive weighing errors

Providing a connection between one to four load cells and a weighing system, the LCI Load Cell Failure Alarm constantly monitors the condition of individual load cells. Manufactured by Aptifirst, this unit prevents the incorrect weighing of product and any subsequent technical and commercial problems by continuous diagnosis of fault conditions.

Many weighing installations are based around multiple load cells, eg a silo or feeder may be mounted on three or four load cells. It is also usual to combine the outputs of these load cells to provide a total weight or force signal to a display or control system. However, should one of the load cells in the system develop a fault, an error in the measured weight will occur which may not be apparent immediately. Designed to overcome this problem, the LCI reports any load cell malfunction immediately by setting an alarm condition output, avoiding incorrect material levels so that there is the continued assurance of product composition.

An on board microprocessor provides a high level of intelligence, enabling the LCI to have a useful range of features. In an alarm condition, a relay contact will change state, the red alarm LED will light and the display will show the load cell in error and an error code. This relay contact may be used to trigger audible and visual alarms to plant operators, and to alert the process control system of the error. A display may be set to show the mV/V value of each load cell or the average of the summed mV/V value of all the load cells, and a security password may be programmed to prevent unauthorised access to the configuration parameters.

An error is detected and signalled if any of the following conditions occur: one or more of the load cells are out of balance; any load cell is operating outside its pre-set mV/V range; the load cell excitation voltage drops from the preset range; any of the load cells become open circuited; or any of the load cells become short circuited. The LCI is powered by the load cell excitation supply, and provides a simulated load cell output with the summed signal to allow signal conditioning instruments to be driven.

Roy Carter, Managing Director, Aptifirst, comments: "The LCI is a very welcome addition to our range of instrumentation. The avoidance of batch wastage or product recall, reduction in plant downtime and increased safety, together with aids for installation and commissioning, will all contribute to the LCI becoming an essential element for all weighing systems."

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