I'm building a simple electrolytic etcher to mark steel parts. The set up is a 12v DC 5 amp power supply with the ground connected to on side of the steel part and the positive connected to a brass lug with and insulated handle. The lug is covered in a felt pad saturated with an electrolytic solution (salt water) and then pressed against the steel part. The idea is this will etch the metal part to create a mark. I'm not getting good results and I want to check how much current is being delivered through the lug. When I try to set up a multi meter to measure amps I get a small spark and freak the meter out. How can a measure the current at the lug?
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1\$\begingroup\$ use resistive current limiting youtube.com/watch?v=ILPQDXV_Rf0 \$\endgroup\$– D.A.S.Commented Jan 19, 2017 at 18:36
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\$\begingroup\$ In what way are the results not good? You could edit your question to include a photo. \$\endgroup\$– Andrew MortonCommented Jan 19, 2017 at 20:51
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\$\begingroup\$ That's the technique I'm looking for, but the DC version where it etches down into the metal, not blackening. What makes it 'resistive' \$\endgroup\$– user28659Commented Jan 20, 2017 at 12:39
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2 Answers
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Connect the meter in series with the lug.
If you're getting a spark, it sounds like you're connecting the meter across the power supply, which is not the way to do it.
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\$\begingroup\$ Yes, I'm being a bonehead and had the meter hooked up incorrectly. When doing it properly I get 7.5a and some other issues. I'll look into it further and post a separate question. thx \$\endgroup\$ Commented Jan 20, 2017 at 12:41
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If you want to take short measurements using your multi-meter in series is fine. However your meter probably has a maximum amount of time indicated in its manual for higher loads before the fuse will blow.
Another way is to get a matching shunt resistor and ammeter. A shunt resistor is a calibrated low ohm resistor designed to have the same resistance over a wide range of temperatures, and the matching ammeter reads the voltage drop over the resistor to display the current flowing. This will allow for a permanent display.
