Hello All,
I would like to develop a testing method to detect window defroster grid failures. Rear windows has 12 heating wires painted to the glass and cca. 2% are faulty pieces. I tried to measure the resistance, current and voltage drop of good parts and compare results with those where was at least 1 broken wire, but the difference was smaller than the tolerance specified by the supplier. (Other problem is that the resistance is greatly depending on the temperature)
Now we are testing visually with a thermal paper/foil but it takes more time and sometimes the operator mistakes or can forget to correctly check the thermo foil. So I need an automated system which blocks broken pieces from further process. It is also very important to not hurt or scratch parts during the testing process, so best option would be contactless testing if possible...
I'am thinking about to make a tool with 12 sensors, 1 sensor to every each heating wire to sense a flowing current in a wire. But I'am not sure that there is any sensor available in the market for such a purpose. Finally PLC have to check the outputs of every sensors, if all the 12 heating wires are good (current is flowing through them) gives visual signal or in case of failure sound alarm or red light flashing...
Here is the specification of rear window defroster:
Power: 167,37W ±10%
Current: 12,87A ±1A
Resistance: 1,0 Ohm -10%/+20%
Wire thickness: 0,48mm
In the attachment you can find the tool used for window checking and cleaning and technical drawing of the window, I placed red dots where I would place the sensors.
I would like to try to use digital hall effect sensors (0 if no current, 1 if any current) because this seems the fastest, the most accurate method and could be easily automated and evaluated with PLC. Could you recommend any appropriate sensor, small and sensitive enough? (current in each wire ~1A, measuring distance >2mm) I have 4cm gap between the window and the tool if I place window into that. Would it be better to use lower voltage or use AC power instead of DC 12V?
I am little bit sceptic about thermo cameras, there could be many confounding factors, I think. (operators hand, fingerprint etc., not enough contrast for the second measurement if the window is already heated...)
Any ideas and suggestions are welcome.
Best regards,
Ate
I would like to develop a testing method to detect window defroster grid failures. Rear windows has 12 heating wires painted to the glass and cca. 2% are faulty pieces. I tried to measure the resistance, current and voltage drop of good parts and compare results with those where was at least 1 broken wire, but the difference was smaller than the tolerance specified by the supplier. (Other problem is that the resistance is greatly depending on the temperature)
Now we are testing visually with a thermal paper/foil but it takes more time and sometimes the operator mistakes or can forget to correctly check the thermo foil. So I need an automated system which blocks broken pieces from further process. It is also very important to not hurt or scratch parts during the testing process, so best option would be contactless testing if possible...
I'am thinking about to make a tool with 12 sensors, 1 sensor to every each heating wire to sense a flowing current in a wire. But I'am not sure that there is any sensor available in the market for such a purpose. Finally PLC have to check the outputs of every sensors, if all the 12 heating wires are good (current is flowing through them) gives visual signal or in case of failure sound alarm or red light flashing...
Here is the specification of rear window defroster:
Power: 167,37W ±10%
Current: 12,87A ±1A
Resistance: 1,0 Ohm -10%/+20%
Wire thickness: 0,48mm
In the attachment you can find the tool used for window checking and cleaning and technical drawing of the window, I placed red dots where I would place the sensors.
I would like to try to use digital hall effect sensors (0 if no current, 1 if any current) because this seems the fastest, the most accurate method and could be easily automated and evaluated with PLC. Could you recommend any appropriate sensor, small and sensitive enough? (current in each wire ~1A, measuring distance >2mm) I have 4cm gap between the window and the tool if I place window into that. Would it be better to use lower voltage or use AC power instead of DC 12V?
I am little bit sceptic about thermo cameras, there could be many confounding factors, I think. (operators hand, fingerprint etc., not enough contrast for the second measurement if the window is already heated...)
Any ideas and suggestions are welcome.
Best regards,
Ate