Fluke Meter - Over Voltage - Broken? - Page 1
Forum section: electronics / testgear

author: bpan
author_rank: Contributor
timestamp: July 06, 2023, 03:46:13 am
content: Here is the scenario. I was testing an outboard motor stator. The stator is puts out a voltage in AC to the ignition Coils. Because the RPM is so fast and most meters can't keep up, we use a DVA adapter. I think it's long name is Direct Voltage Adapter. It basically holds the peak voltage recorded in DC volts.Anyhow the motor was having issues, and the voltage was going up into the 600v range, when I assume it spiked. The meter went blank, and the voltage scale reset itself to 6v instead of 1000v. This happened a couple times. Then I stopped.The meter seems fine, but I'm still worried. Any ideas?The meter is an 88v

author: floobydust
author_rank: Super Contributor
timestamp: July 06, 2023, 03:53:57 am
content: Did you hear the screams of pain from the multimeter?

author: bpan
author_rank: Contributor
timestamp: July 06, 2023, 04:08:19 am
content: I did not hear any actually, although they would have been tough to hear over my internal screams of pain.

author: bdunham7
author_rank: Super Contributor
timestamp: July 06, 2023, 04:08:24 am
content: If you are working with primary ignition systems, you can get fast, high-voltage moderate energy pulses that don't burn the front end but propagate internally and reset the MCU. You could also possibly have damage to small semiconductors like diode clamps or the EEPROM that the calibration data is stored in. If the meter works OK and appears to be accurate, then it likely is just fine. However, I wouldn't use it that way anymore.

author: floobydust
author_rank: Super Contributor
timestamp: July 06, 2023, 04:25:29 am
content: It sounds like the high voltage, fast edge waveform just made the multimeter crash and reboot. Not sure what a DVA adapter has inside.Your test setup has a lot of EMI and common-mode noise that will cause most multimeters to crater. They need that inside foil shield.The 88 has good overvoltage protection, and when that fails it will read incorrectly. Try out all its functions to make sure.

author: bpan
author_rank: Contributor
timestamp: July 06, 2023, 02:40:51 pm
content: Thank you all for the responses, I will quit using my Fluke for that, and go back to my analog meter. I think that would be better.

author: floobydust
author_rank: Super Contributor
timestamp: July 06, 2023, 05:53:46 pm
content: An ignition stator coil outputs up to 500V peak when supplying power to CDI, so it is not at all easy to test.A coil resistance measurement does not tell you much about the magnets, coil insulation etc.A "Direct Voltage Adapter" seems to be just a 1/2 wave rectifier diode+cap+resistor which works as a peak detector.I think your multimeter is OK but the DVA may have blown up. A 600V reading means the cap inside must have popped. Take it apart, post picsedit: I did check the Fluke 88 Automotive Meter schematic and the voltage channel is well protected. Above 1,000V for a long time it will start to burn a resistor inside.Because CDI is very noisy and makes a lot of interference, it was likely too much spikes (for almost any multimeter) when connected to the stator coil hot side, so it crashed.

author: Axtman
author_rank: Regular Contributor
timestamp: July 06, 2023, 06:39:42 pm
content: The Fluke 88 is NOT a true RMS meter but instead is an averaging meter. So if your AC signal is not a clean sine wave you will get weird results.