Consultation Hotline
+1 (302) 618-8777
+1 (302) 618-8777
Automatic checkweighers are widely used in pharmaceutical laboratories and production environments to verify the weight of tablets, capsules, vials, bottles, packaged medicines, and other pharmaceutical products. Accurate weighing is essential for quality control, dosage verification, packaging inspection, and compliance with laboratory quality requirements. However, checkweighers may experience unstable readings, incorrect rejection, mechanical failures, communication errors, or calibration problems during operation. This article introduces common faults and practical troubleshooting methods.
One of the most common problems is that the displayed weight continuously fluctuates even when the sample remains in the weighing position.
Possible causes include vibration, air movement, an unstable installation surface, excessive electrical interference, or an improperly installed load cell. In pharmaceutical laboratories, nearby pumps, centrifuges, mixers, or HVAC systems can transmit vibration to the weighing platform.
First, check whether the checkweigher is installed on a stable and level surface. Remove unnecessary vibration sources and make sure the weighing platform does not contact surrounding equipment. The weighing area should also be protected from strong airflow.
If the problem continues, inspect the load cell and its cables. Loose connectors, damaged cables, moisture, or contamination can cause unstable signals. After correcting the mechanical problem, perform zero adjustment and calibration according to the manufacturer's procedure.
If the checkweigher consistently displays a weight that differs significantly from the reference weight, calibration should be checked first.
Place a certified test weight on the weighing platform and compare the displayed value with its actual mass. If the deviation exceeds the specified tolerance, perform calibration using an appropriate certified standard.
Incorrect tare settings can also cause systematic errors. Check whether the container or packaging weight has been properly accounted for. In addition, verify that the selected weighing range and product recipe are correct.
The weighing platform should be clean and free of powder, tablets, packaging fragments, or other materials that could interfere with measurement.
If the equipment cannot start, first check the main power supply, emergency-stop button, circuit breaker, and power switch.
A loose power cable or blown fuse may prevent the system from powering on. If the display is completely blank, check the incoming voltage and internal power supply only if this can be performed safely by qualified personnel.
For systems equipped with safety interlocks, guards, doors, or protective covers, make sure all safety devices are correctly closed and activated. Some checkweighers will not start when a safety interlock is open.
If the control panel displays an alarm code, record the exact code before resetting the system. Repeated alarms should be investigated rather than continuously cleared.
A checkweigher may correctly measure product weight but incorrectly reject acceptable products or allow unacceptable products to pass.
This problem is often related to incorrect upper and lower weight limits, an incorrect product recipe, delayed rejection timing, or improper sensor positioning.
Verify the nominal weight and tolerance settings in the control system. Check whether the correct product program has been selected.
Then inspect the conveyor speed and reject mechanism. If the rejection timing does not match the product position, the system may reject the wrong item. Optical sensors should be cleaned and correctly aligned.
For pneumatic rejection systems, check air pressure, tubing, solenoid valves, and the reject cylinder. Insufficient air pressure may cause incomplete or delayed rejection.
A conveyor that stops unexpectedly or operates at an unstable speed can directly affect weighing accuracy.
Check the conveyor belt for excessive tension, contamination, mechanical obstruction, or misalignment. Pharmaceutical powders and packaging materials can accumulate around rollers and guides.
The motor, drive system, and speed-control components should also be inspected. If the conveyor speed changes during weighing, the available weighing time may become inconsistent.
Make sure the product spacing is appropriate. Products that touch each other or enter the weighing area too closely may cause incorrect measurements.
Photoelectric sensors are commonly used to detect product entry, positioning, and rejection. Dust, powder, liquid contamination, or incorrect alignment can prevent reliable detection.
Clean the sensor surfaces using an appropriate method and check the alignment between the transmitter and receiver. Confirm that the sensor status changes correctly when a product passes through the detection area.
If the sensor indicator remains continuously ON or OFF, inspect its cable and connector. A damaged sensor may need replacement.
Modern pharmaceutical checkweighers may communicate with laboratory information systems, production management systems, PLCs, barcode scanners, or other instruments.
Communication failures may result from incorrect network settings, disconnected cables, software configuration problems, or incompatible communication parameters.
Check Ethernet or serial connections and verify the configured IP address, communication protocol, and data format. If the system uses software recipes, confirm that the correct product configuration has been loaded.
Before making software changes, save existing configuration parameters and system settings whenever possible.
Regular preventive maintenance can significantly reduce checkweigher failures. Daily inspections should include cleaning the weighing platform, checking sensors, inspecting the conveyor, and confirming zero stability.
Periodic maintenance should include calibration verification, load-cell inspection, electrical connection checks, conveyor inspection, and functional testing of the reject mechanism.
Because pharmaceutical laboratories have strict hygiene and quality requirements, cleaning procedures should follow the equipment manufacturer's recommendations and the laboratory's validated SOPs.
Automatic checkweigher faults can originate from the weighing sensor, mechanical structure, conveyor, sensors, electrical system, software, or environmental conditions. Troubleshooting should therefore proceed systematically: check the environment first, then mechanical components, sensors, electrical connections, calibration, software settings, and finally replace defective components when necessary.
Accurate records of alarms, calibration results, maintenance activities, and replaced components are also important for pharmaceutical quality management. With regular calibration, proper cleaning, preventive maintenance, and standardized troubleshooting procedures, automatic checkweighers can maintain reliable weighing performance and reduce unnecessary downtime.