- #1
jeffamm
- 26
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I'm evaluating a wall-transformer type power supply used to power guitar effect pedals as a replacement for a 9V battery. It's rated at 9V and 2000 mA. I put resistive loads on it of (nominally) 16, 8 and 4.5 ohms, and made measurements with a Klein Tools MM1000 multi-meter. Here's what I got:
Load DC V DC I AC mV
None 9.14V 0A 280-305 varying
16 ohms 9.01V .56A same
8 ohms 8.87V 1.11A same
4.5 ohms 8.67V 1.88A same
I measured the AC millivolts in hopes of characterizing the ripple voltage but I found the readings varied from 280mV to 305mV after about 5 minutes, and didn't change when the loads where changed. I thought I might just be measuring noise, and unplugged the transformer to see if the AC reading went to zero (it did) but I don't know if that proves anything. I don't have access to an oscilloscope. Is there a better way to measure ripple and can I conclude anything from my measurement?
The DC output voltage varied by about 5% with loads. Is that good, bad or typical for battery replacement power supplies? Any other observations about the data?
thanks in advance for any help
Load DC V DC I AC mV
None 9.14V 0A 280-305 varying
16 ohms 9.01V .56A same
8 ohms 8.87V 1.11A same
4.5 ohms 8.67V 1.88A same
I measured the AC millivolts in hopes of characterizing the ripple voltage but I found the readings varied from 280mV to 305mV after about 5 minutes, and didn't change when the loads where changed. I thought I might just be measuring noise, and unplugged the transformer to see if the AC reading went to zero (it did) but I don't know if that proves anything. I don't have access to an oscilloscope. Is there a better way to measure ripple and can I conclude anything from my measurement?
The DC output voltage varied by about 5% with loads. Is that good, bad or typical for battery replacement power supplies? Any other observations about the data?
thanks in advance for any help