Products > Test Equipment
HP 66332A Output Off but still loading source
rommac100:
Not sure if this a just a limitation of the PSU but for whatever reason my HP 66332A (well two of them) exhibits this issue where the output can be set off but will still draw current from a source. It is voltage dependent on the source so 20V source will equate to about 20mA current draw and 1V source is somewhere around 1 mA. Not sure what the issue could be immediately but any assistance would be appreciated.
Berni:
Id need to go check on mine. But it sounds normal.
But in general it is typical for most PSUs to have some loading on the output when it is disabled. Some of it is because most of the sensing circuitry is still connected. But commonly they are loaded down on purpose to help discharge the output capacitors, since otherwise the output voltage might remain present for a good while after being turned off.
Some rare PSUs even actively pull down the output. I have a big 4 channel rack mount HP system PSU that pulls down the output using full rated output current.(Tho forgot if it does that in disabling or just programing to 0V output). The one you have does that at the set current for the channel, so it is pretty useful as a electronic load too.(I mostly just use it for that, since it is a pretty annoying PSU to use)
J-R:
I just checked mine and it does not do this. There is an initial current flow spike when the other PSU is set to 20V, but it drops to zero after a few seconds. End result current flow is below 0.001mA. I'm confident the spike is due to charging the 66332A's output capacitance (there are two settings for this value).
Just to double-check, you actually have the output disabled, and are not just setting the voltage/current to zero?
J-R:
Tinkered some more and it looks like my 66332A is a completely open circuit when the output is disabled, and I can hear the relays. The current flow was from the other power supply's output capacitance, not the 66332A's.
Swainster:
I have a couple of 66311Bs and they both do this - when the ouput is disabled they pull down with about the equivalent of a 330R resistor. This is different to programming 0V, when they pull down with pretty much the full capability of the down programmer (doesn't follow the current limit setting).
edit: My units don't have the relay option - perhaps this makes a difference?
Navigation
[0] Message Index
[#] Next page
Go to full version