Rigol DP 832 Unexpected results using "tracking Feature" (both supplies parallel - Page 1
Forum section: electronics / testgear

author: Julio2784
author_rank: Newbie
timestamp: November 01, 2023, 09:22:33 pm
content: I attempted to wire both 30 Volt supplies in parallel, to obtain a max current of 6 Amp (3 Amp each) I went ahead and turned on "tracking"and wire the supplies in parallel. (See photos)I was very disappointed to find that currents were NOT shared equally, the maximum current possible was 4.7 AMP (see photos)Was my unit defective? can other Rigol DP 832 owners comment on this?

author: thm_w
author_rank: Super Contributor
timestamp: November 01, 2023, 09:30:47 pm
content: Tracking just means the voltage will track, it doesn't mean the current will be shared evenly. The output with the higher voltage will source more current. Though other supplies may operate differently.The maximum current should be 6A though, try shorting the outputs together directly with the banana leads, instead of going to whatever load it is you have hooked up.BTW you can hack the unit to unlock an extra digit if you want:https://www.eevblog.com/forum/testgear/need-help-hacking-dp832-for-multicolour-option/msg4028779/#msg4028779

author: RoGeorge
author_rank: Super Contributor
timestamp: November 01, 2023, 10:03:38 pm
content: I suspect most of the imbalance is from the external wire bridges that connect the two channels. DP832 has compenstion wires internally tied to the output connectors. Also, there are some GND bridging issues with the GND bridged internally, between CH2 and CH3, not sure if those are supposed to affect your setup.What I would try:- make sure the bridges are firmly tight and making good contact, and that the wires are made of solid copper and not just copper plated- tie together all the GND connectors, including the GND from the 3rd channel, and including the earth grounding banana- connect both + and - wires to the bananas of a single channel, try either CH1 or CH2 to see in which channel the current gets a better distribution- If you have 2 pairs of wires for the load, use 2 pairs instead of just one and connect each pair to a channelCould also be a wrong calibration in the DP832, but that would be highly unlikely, verify the bridges first, and use 4 wires to the load instead of only 2, if possible.Another way to raise a little the total current would be to set the max current to 3.2A on each channel, so instead of 3.0+1.7 max current, you'll get 3.2 + 1.9, so instead of only 4.7A you'll get 5.1A in total.

author: macboy
author_rank: Super Contributor
timestamp: November 02, 2023, 02:28:49 pm
content: How do you know that is the max? Did you try going higher? In my experience (NOT with this Rigol but many other supplies), it is normal for one of the two supplies to max out first. One will have a slightly higher output voltage than the other, and it will supply more (or all) current as a result. When that one reaches the current limit, its voltage will drop as a result, and the other side will take up the slack. This can be illustrated in an obvious way if you set one supply to say 5.00 V and the other to 5.10 V, then connect them in parallel, and vary the load.

author: Chalcogenide
author_rank: Regular Contributor
timestamp: November 02, 2023, 03:48:05 pm
content: Tracking is generally meant to produce a symmetric positive/negative rail, and as such the ACTUAL voltage will be forced to be equal on the two channels, so if a channel enters current limit, the other channel will lower its output voltage as well, meaning that you might not get full output current. For parallel operation you would want the voltage to be SET equal, and allow one of the two channels to enter current limit mode, with the other channel still in CV. Sadly it seems that the Rigol power supply does not have a dedicated way of setting both channels equal without them being in tracking mode. You might be able to do it by controlling the instrument remotely and setting both channels independently at the same voltage.If you are looking for a simple fix, I would try moving the bananas until you find the position that maximizes output current, or by connecting them together at the load and not at the source.