Automated GNS Measurement System Tester with Bespoke PWM Signal Conditioning
Sector:
OEM & Special Purpose Machinery, Automotive
Type:
New Build - Control System, Software
Platform:
Siemens
Certification:
CE / UKCA
Summary
DelaControl designed, built, programmed and commissioned a bespoke automated test system for a GNS measurement device, replacing a legacy tester that was no longer available or supported. The system included a Siemens PLC-based control panel, PLC and HMI software, a bespoke PWM signal conditioning PCB, and on-site commissioning to integrate the tester with the customer's network infrastructure and data logging systems.
Challenge
The customer required a replacement for an end-of-life test system used to carry out post-production testing of a GNS measurement device. The original tester was no longer available or supported, leaving a gap in the production verification process.
The new system needed to read a PWM signal that varies with gearshift position, determine the correct gearshift state, and step through a structured test sequence — providing a clear pass or fail result to the operator at each stage. Test results, serial numbers, and date/time information were required to be automatically stored to a CSV file on a networked server, requiring a hardwired network connection.
As the project developed, tighter signal accuracy requirements were identified: the system needed to meet a tolerance of ±0.1% against calibration reference (golden) samples, with the ability to re-calibrate the signal conditioning hardware against those samples in the field.
Solution
DelaControl designed and built a wall-mounted IP66-rated control panel on a Siemens platform, housing a Siemens S7-1200 series PLC with digital and analogue I/O expansion modules. The enclosure was designed to allow both hardwired and plugged connections without opening the cabinet, and the panel was built and tested at DelaControl's Bristol facility ahead of a customer factory acceptance test (FAT).
To meet the tighter PWM signal accuracy requirement, DelaControl designed and manufactured a bespoke PWM signal conditioning PCB — integrated into the system to achieve the required ±0.1% tolerance against the customer's golden calibration samples, with an adjustable calibration function built in.
PLC and HMI software was developed to automate the full test sequence, with operator-facing pass/fail feedback at each test stage and automatic logging of results, serial numbers, and timestamps to a CSV file on a remote server. Following hardware delivery, a DelaControl controls engineer attended site to commission the system's network integration, configuring communication between the tester and the customer's servers and databases.
A full documentation package was supplied, including electrical schematics (produced in EPLAN), general arrangement drawings (AutoCAD LT), thermal calculations (Rittal Therm), a Declaration of Conformity to the Low Voltage and EMC directives, and a signed FAT certificate.
Key Facts
• Siemens S7-1200 PLC with digital I/O expansion and analogue I/O module
• Wall-mounted IP66-rated enclosure (Rittal AX series, 380 × 380 × 210 mm)
• Bespoke PWM signal conditioning PCB with ±0.1% tolerance against golden calibration samples and adjustable calibration function
• Three LC Technology LM358 PWM-to-voltage converter modules
• Hardwired network connection for automated CSV data logging to remote server
• On-site commissioning visit for network, server and database integration
• ILME multi-pin connectors for tool-free external connections without opening the cabinet
• Full documentation pack: EPLAN schematics, AutoCAD GA drawings, thermal calculations, Declaration of Conformity, FAT certificate