Products > Test Equipment

E36300 Series Programmable DC Power Supplies (E36311A, E36312A, E36313A)

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Ahrenp:

--- Quote from: adamgreig on December 11, 2017, 05:06:11 pm ---I think the hum might be the fan occasionally spinning up?

--- End quote ---

It's don't think it's the fan, I can hear the fan ramp up when I power it on and the hum remains in the background. It's not a huge deal but when I'm on my nearby PC (which is dead silent) with nothing else in the room on, there's just a slight, annoying hum. I was just curious if it was typical of these power supplies. If everything is turned off I might start flipping off the power bar because I don't see any reason for it to be humming and drawing 10W all the time.

HighVoltage:

--- Quote from: nctnico on December 11, 2017, 05:27:34 pm ---Why would you want to use the knob to adjust the voltage? On PSUs with a keypad I just punch the number in. Much quicker and easier.

--- End quote ---
Usually I also just enter the numbers on the keypad and it works really well.
Finally a Keysight PSU with a keypad !

But the other day I needed to ramp up the voltage in mV steps and used the knob, expecting every step to be 1 mV change. But then to my surprise this was not a linear increase. May be it is nitpicking?

Fgrir:

--- Quote from: HighVoltage on December 11, 2017, 05:03:05 pm ---The voltage turning knob can increase the output by 1mV per indent.
But the real output is not increasing by the same amount for each indent.
In other words, there is a big difference between the set point the actual readout and what is measured externally with a different meter.

--- End quote ---
I've been eyeing these supplies for a while so I'm curious, how big a step size are you actually seeing with your 1mV setting changes?

The front panel controls are all spec'd with 1mV steps, but the remote programming resolution for the E36312A is 0.36V for the 6V output and 1.5mV for the 25V outputs.  Perhaps these represent the real hardware resolution (14 bits???), and all you are seeing is the quantization error of mapping the 1mV steps onto this.

Of course if you are seeing larger steps then this wouldn't be an explanation at all...

adamgreig:
A while ago I ran a little test with the E36312A ch1 hooked up to my 34465A, and recorded the difference between measured voltage on the '65, and both the programmed and readback voltage on the 36312A. I did it over a few spans but this first one is the only one with mV steps. Also attached is over the whole 0-6V span. It's not bad all around, error tends to be within a fraction of a mV.

nctnico:

--- Quote from: Fgrir on December 11, 2017, 08:03:12 pm ---
--- Quote from: HighVoltage on December 11, 2017, 05:03:05 pm ---The voltage turning knob can increase the output by 1mV per indent.
But the real output is not increasing by the same amount for each indent.
In other words, there is a big difference between the set point the actual readout and what is measured externally with a different meter.

--- End quote ---
I've been eyeing these supplies for a while so I'm curious, how big a step size are you actually seeing with your 1mV setting changes?

The front panel controls are all spec'd with 1mV steps, but the remote programming resolution for the E36312A is 0.36V for the 6V output and 1.5mV for the 25V outputs.  Perhaps these represent the real hardware resolution (14 bits???), and all you are seeing is the quantization error of mapping the 1mV steps onto this.

--- End quote ---
You have a very valid point here and something very similar is going on with HP's older telecom DC power supplies like the 66311B. The programming and readback accuracy are different. Add the inaccuracies of the circuitry to that and it is clear that changing the setting (=programming) by 1mV isn't going to match the readback reading.

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