A manufacturer of agricultural tires required a method for monitoring the internal pressure of a tire during the fabrication process. The dynamic and physically obstructive nature of the tire curing machinery made conventional wired sensors impractical and unreliable. A wireless pressure measurement system was identified as the ideal solution, providing a robust and easily integrated method for critical process control.
- Application: Real-time pressure monitoring inside a tire during the curing process.
- Challenge: The rotating and metallic structure of the curing press made cabled sensors unfeasible and created a challenging environment for radio frequency (RF) signals.
- Solution: A battery-powered wireless pressure transmitter paired with a single-channel receiver and a high-gain external antenna.
- Benefit: Enabled reliable, real-time data acquisition for quality control, eliminating cable failures and overcoming RF signal attenuation from surrounding machinery.
In the fabrication of large agricultural tires, the curing process is a critical stage that determines the final quality and structural integrity of the product. During this stage, an uncured “green” tire is placed into a large metal press. An internal bladder is then inflated with a medium such as hot water or steam. The pressure exerted by this bladder forces the raw rubber into the intricate details of the press mold, forming the tire’s tread and sidewall patterns. Precise control and monitoring of this internal pressure are paramount to ensure a uniform cure and prevent defects.
A customer in this industry faced a significant challenge in obtaining this critical pressure data. The use of traditional wired pressure transducers was not feasible due to the machinery’s nature. The tire and mold assembly can rotate during the process, and the presence of moving components would make any physical cable a point of failure, subject to damage and costly production stoppages. Furthermore, the environment is dominated by large metal structures, which creates a significant challenge for wireless signal transmission. The customer required a robust, cable-free solution that could reliably transmit low-range gauge pressure readings from the press to their central control system.
The proposed solution consisted of an IWPTU series wireless pressure transducer and an IWR-1 single-channel wireless receiver. The IWPTU transmitter, with its piezoresistive ceramic sensor and 316 stainless steel housing, is built to withstand harsh industrial applications and is compatible with a wide range of media. The transmitter is battery-powered with a life of up to five years at a standard 10-second transmission rate, minimizing the need for maintenance in a hard-to-access location. The user also has the flexibility to change the transmission update rate to values of 1, 5, or 30 seconds to better match their process cycle times or to conserve battery life.
A key element of this solution was addressing the RF-hostile environment of the tire press. While the system can achieve a line-of-sight range of up to 500 meters with standard antennas , the significant metal mass of the press can block or attenuate the 2.4 GHz signal. To overcome this, the solution included a 6dBi high-gain external antenna for the receiver. This antenna, connected via a one-meter cable, allows the antenna itself to be positioned away from the press and other obstructions, ensuring a clear and reliable signal path from the transmitter.
The IWR-1 receiver provides a simple and effective interface to the plant’s existing control system. It offers user-selectable analog outputs of either 4-20mA or 1-5V DC, which can be wired directly to a PLC or data acquisition system as a direct replacement for a conventional wired sensor’s output. The entire system is designed for plug-and-play simplicity, with easy pairing between the transmitter and receiver accomplished via DIL switches. For advanced control, the receiver also features a 5-Amp rated changeover contact that can be configured as a process alarm. This can be set to trigger if the pressure goes outside of set limits, if the signal from the transmitter is lost, or if the transmitter’s battery is running low, providing multiple layers of diagnostic feedback for robust process control and preventative maintenance.
IWPT Wireless Pressure Sensor with IWR-1 Single Channel Receiver
- Part No: IWPTU-GP015-00, IWR-1, ANT4000, II-BATT
- Wireless Transmitters: Pressure Sensor
- Process Connection: 1/4 NPT male
- Pressure Ranges (psi): 15 psi g
- Wireless Receivers: Single channel 1-5V or 4-20 mA output
- Optional Extras: 6dBi external mount antenna for increased wireless range, Spare Tx battery