Voltage and Current Panel Meters
I saw these on eBay, and thought it would be handy for observing both the voltage and current draw on my KiwiSDRs, so I ordered two:
They just arrived today, and I wired them in. One of my linear supplies is powering five KiwiSDRs, and they are drawing 3.3 amps total. The voltage drop across the current shunt on the meter is 77 mV, not fantastic, but tolerable. Just tweak the output voltage a little 😀
The second supply reads 1.3 amps with two KiwiSDRs, a netSDR, and a Thunderbolt 10 MHz GPS reference.
Obviously your power supply output needs to be floating relative to AC power for these meters to measure current.
The meters did require some minor surgery. It is tough to tell from the photo, but the current shunt interferes with proper latching of the current sense connector. So I had to heat the solder joints to bend it a little, so the connector clears.
Comments
It should be noted that these measure the current in the low (V-) side, and would be more useful of they did so in the V+ side - but what can you expect for the price!
Tom, WA2TP tried using these to monitor current of individual KiwiSDRs, but got nonsensical values, finally realizing that since they shared a common power supply - and that these devices measured in the negative lead - the V- was shunted via coaxial cable connections and DC earth/ground loops, effectively making them usable only if each and every KiwiSDR were to have its own power supply with completely isolated DC outputs.
Using them as you describe - measuring the entire lot of receivers - should work fine, as long as the V- side of the supply is not earth-referenced.
Does your power supply have sense lines? You might consider a supply that has them for your application. It will compensate for V drop in the cables. It will also prevent an overvoltage condition which could happen if you cranked it up and then had one or more of the loads drop off.
I adjust the PSU voltage to 5.0V while monitoring the power pins on the USB-A port of the BB