EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: brock on December 22, 2021, 10:59:33 pm
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Hello EEVblog folks,
I have a Brymen 869s and I used it to measure the duty cycle of a 208 VAC sine wave signal, which I plan to modulate with a dimmer circuit.
My question is, would the meter be damaged if there was a 208 VAC signal present on the meter's inputs, while the meter is set to the DCmV or Duty% function? I was able to measure the 50% duty of the signal before modulating it. No signs of damage and no burnt smells. I was only a bit worried when saw the battery icon flashing. The manual doesn't state what causes that but I wonder if this is an indication of a fault, damage or simply telling me that I was using the wrong scale/range.
It seems like this function is intended to be used on low voltage circuits based on what the manual states: " Range: 0.1% to 99.99% / Accuracy: ± (3 digits/kHz + 2 digits) / Input Frequency: 5Hz -- 500 kHz, 5V Logic Family". Still, I would like to know if the specified "Input Impedance: 10M, 60pF nominal (80pF nominal for 500mV range)" still applies and protects the meter while in this function.
Any thoughts?
Thanks for reading,
Brock
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The meter is protected to 1000V on those ranges so no damage should occur.
OTOH The frequency ranges are designed for 5V logic so it's probably a good idea to pass the signal through a voltage divider first. That way you won't be triggering the meter's protection circuitry, which could interfere with the readings.
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OTOH The frequency ranges are designed for 5V logic so it's probably a good idea to pass the signal through a voltage divider first. That way you won't be triggering the meter's protection circuitry, which could interfere with the readings.
Does it not display ACV and Hz at the same time?
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OTOH The frequency ranges are designed for 5V logic so it's probably a good idea to pass the signal through a voltage divider first. That way you won't be triggering the meter's protection circuitry, which could interfere with the readings.
Does it not display ACV and Hz at the same time?
Yes, but the Hz on AC volts range is different from the 5V, Hz/duty-cycle range.
The OP mentioned duty cycle measurement and the 5V range, so... :-//
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The OP mentioned duty cycle measurement and the 5V range, so... :-//
I had to look at a picture of the front of an 869S to figure out what you are referring to. So the Hz/%/ms (does it have pulsewidth?) function set is only available on the mVAC range, the other AC ranges only have Hz. That seems....odd. Or at least not what I'm used to and I'm not sure why it would be that way. And of course you're right, you can't go slamming 208VAC into the mVAC range and expect good things.
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the Hz/%/ms (does it have pulsewidth?) function set is only available on the mVAC range, the other AC ranges only have Hz. That seems....odd. Or at least not what I'm used to and I'm not sure why it would be that way.
The mV range has higher bandwidth (Hz up to 1MHz), it's probably needed for the pulse width measurement.