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I recently acquired a used BK Precision 1660 triple output power supply.

Upon powering it up, I did some basic voltage checks. On both the master and slave outputs, voltage between positive and negative terminals were correct.

However, on the slave output, I actually measured 0.25V between the positive terminal and ground, and also -0.25V between the negative terminal and ground. This doesn't happen on the master output.

Is this normal?

I'm somewhat new to these things but something tells me this isn't right

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  • \$\begingroup\$ Sorry, for whom doesn't know the instrument: could you please specify what did you expect the voltages to be? \$\endgroup\$ – clabacchio Dec 3 '12 at 9:58
  • \$\begingroup\$ I would expect there to be zero voltage between positive and ground, and also zero voltage between negative and ground. The way I understand it, the power supply sets up a potential difference between the positive and negative terminals. The ground terminal is simply connected to earth ground. It seems to be common to connect negative and ground, if you want a positive reference above ground. Or you can connect positive and ground, and then get a negative reference to ground. \$\endgroup\$ – up_the_irons Dec 3 '12 at 10:02
  • \$\begingroup\$ If I'm measuring a potential difference between black terminal and green terminal, then that strap will carry current, which doesn't seem normal. \$\endgroup\$ – up_the_irons Dec 3 '12 at 10:52
  • \$\begingroup\$ You can get the manual here: k7jrl.com/pub/manuals/b&k/1660 \$\endgroup\$ – up_the_irons Dec 3 '12 at 10:53
  • \$\begingroup\$ let us continue this discussion in chat \$\endgroup\$ – clabacchio Dec 3 '12 at 11:00
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The outputs are almost floating with respect to ground but a tiny feedback current both +/- will show the voltage with respect to ground as an offset when only loaded with a 10MOhm probe.

My guess is that is normal for your old model and wont have any impact in most applications. I suspect newer models improved that leakage. But this wont stop you from using tracking mode or Independant or CV , CC or same or complementary polarity earthed at any one point.

Typical use in the old days was separate Analog and Digital grounds wires but the complementary 0~24V outputs grounded at the PSU only with the 5V logic ground, so they do not share logic current noise.

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