# Test current carrying capacity of conductor

For research purposes, I would like to determine how much current a conductor like a line of conductive ink would be able to carry. What is a good and safe way to test this?

• Apply current and look what happens? Commented Jul 7, 2017 at 9:50
• But I don't want it to get so hot that the paper starts catching fire. Is there a safe way that I can test this? Commented Jul 7, 2017 at 9:51
• add a thermocouple linked to a cutout, Commented Jul 7, 2017 at 9:53
• Keep a watch on temperature. Run a destructive test. Then run up to 90% of the temperature value of the destructive test and measure current. Ray Bradbury might have some clues to the destructive temperature, at least on book stock. Ultimately though, that isn't the question you asked, you wanted the current capacity of the conductor, not the system. Commented Jul 7, 2017 at 10:13
• A safe way to test it is to do it outdoors, on concrete, away from fuel stores and rubbish bins, so that when the conductor or anything in contact with it catches fire, that's the only thing that catches fire. Commented Jul 7, 2017 at 11:24

You probably need to work out the maximum allowable current density in A/mm² of printed trace cross-section. This will give you a figure you can reuse in further calculations.

If faced with the problem I would try a few approaches:

• Print multiple identical test samples.
• Use a lab power supply and monitor and record the current as a function of voltage. This will give you a temperature coefficient of resistance which may also be useful.
• Test to destruction, recording test conditions such as airflow, ambient temperature, lying on table or hanging in the air, face up / down, etc.

Figure 1. Infrared thermal imaging cameras are used in industrial monitoring of electrical equipment. Source: Fluke.

• If possible use an infrared thermal imaging camera to measure the temperature of the element or paper. Be careful to use the correct emissivity factor: shiny metals will have a low value so it may be advantageous to measure the temperature of the back-side of the paper which should have an emissivity value of around 0.95 which is the default for most IR instruments.
• If you can't get access to a sensitive and accurate infrared sensor, you probably will not get adequate results. You also need information about the deterioration of the materials vs. temperature. If you have made the ink yourself, you will need to make multiple tests over long periods of time. You may need a microscope.
– user80875
Commented Jul 7, 2017 at 12:17
• A finger is a pretty good device too. It will restore itself, in a week or two :-). A thermally-sensitive tape is also an option. Commented Jul 10, 2017 at 22:24