Valmet IQ Basis Weight SH Sending Assembly – Model A418081 Ver.3.0

The Valmet IQ Basis Weight SH Sending Assembly, part number A418081 and revision 3.0, is a critical component of the Valmet IQ quality control system. This sending unit is responsible for transmitting the basis weight measurement signal from the scanning sensor head to the processing electronics, using a high‑reliability SH (signal handling) interface. It is designed specifically for measuring the basis weight (grams per square meter) of paper, board, and pulp sheets in real‑time, ensuring precise product quality management.

Measurement Principle and Sensor Integration

The sending assembly works in conjunction with a beta‑ray or X‑ray sensor (depending on configuration) that measures the attenuation of radiation through the sheet. The A418081 contains the pre‑amplification stage, signal conditioning, and analog‑to‑digital conversion for the sensor signal. It also houses the reference detector and temperature compensation circuits to maintain accuracy despite ambient variations. The Ver.3.0 revision introduces an enhanced digital filter that reduces noise from sheet flutter and improves measurement stability.

Signal Processing and Output

The assembly processes the raw sensor signal and outputs a linearized 4‑20 mA analog signal proportional to the basis weight, as well as a digital data stream over the IQ bus. It supports both current and voltage output modes (user‑selectable). The internal resolution is 16 bits, providing a measurement resolution of 0.01 g/m². The update rate is 500 Hz, allowing fast response to web variations. A built‑in self‑diagnostic routine continuously monitors sensor health and flags errors via a status relay.

Calibration and Standardization

The sending assembly includes a calibration reference that can be activated automatically at set intervals. It supports both zero and span calibration using internal standards, and the calibration coefficients are stored in non‑volatile memory. The Ver.3.0 adds an automated drift compensation that adjusts for sensor aging. Field calibration can be performed using the IQ system software, which guides the operator through a step‑by‑step procedure.

Electrical and Mechanical Design

The A418081 is housed in a rugged aluminum enclosure rated IP65, designed for mounting on the scanning frame near the sensor head. It measures 180 mm x 120 mm x 60 mm and weighs 1.5 kg. The assembly uses a 24 V DC power supply (18‑32 V) with a maximum current of 0.5 A. Connections are made via military‑grade circular connectors for power, signal output, and communication. The internal PCB is conformal coated to resist moisture and paper dust.

Communication and Integration

The sending assembly communicates with the IQ system controller via a CAN‑based fieldbus, using a proprietary protocol. It transmits both measurement data and diagnostic information. The module supports remote configuration of parameters such as measurement range, damping, and output scaling. It is fully compatible with the Valmet IQ Profiler and can be integrated with existing quality control networks.

Environmental and Reliability

Operating temperature: ‑10 °C to +50 °C; humidity: 5‑95 % non‑condensing. The unit is tested for vibration (2 g) and mechanical shock (30 g). It meets CE and FCC emission standards. MTBF is estimated at 500,000 hours under normal mill conditions.

Installation and Commissioning

Mount the sending assembly on the scanner carriage, ensuring proper alignment with the sensor. Connect the sensor cable and power/signal cables. Use the IQ service tool to assign the unit address and configure measurement parameters. Perform a zero calibration with no sheet and a span calibration using a known standard weight. Verify the output signal at the controller.

Typical Applications

This component is used in all paper and board machines where basis weight control is critical, including fine paper, newsprint, and board grades. It also finds application in non‑woven and pulp drying lines.

Maintenance and Troubleshooting

Routine maintenance includes cleaning the sensor windows and checking cable connections. The assembly provides LED status indicators for power, communication, and fault. If the output is erratic, check the supply voltage and sensor alignment. The diagnostic log can be accessed via the IQ software to pinpoint issues.

Conclusion

The Valmet IQ Basis Weight SH Sending Assembly A418081 Ver.3.0 offers accurate, reliable signal transmission for basis weight measurement. Its robust design and advanced diagnostics make it a key element for maintaining product quality in the paper industry.