Is it still possible to buy / find V2 compatible power clamps?
I have a new setup where I would love to measure additional imput on my flukso FLM02A.
The ones listed in the shop are incompatible with the V3 so if someone can help me out would be greatly appreciated.
KR
Dieter
Anyone anything for sale or an extra clamp lying around?
I’ve got 3x spare here in Australia. I purchased these in addition when I thought I had lost the originals in a house move.
I’d be keen to know where I can get a V2 pulse reader in australia. Ideas?
hI B20,
Do you still have the clamps for sale?
Looking for 2x 50A v2 clamps too. Does anybody know the specs ? I would guess that similar clamps are available on some chinese site somewhere... (a direct link to such a site would even be better ;-) )
If you are a bit in Ohm's law, then this hint might help: The V2 current clamps have an impedance of 6k8 Ohms; they provide an equivalent voltage output signal of 0 to 5V with respect to the current measured. This means, a clamp with 50A measurement range maps these 0 to 50A proportionally to 0 to 5V. Internally on the sensor board the clamps are connected to the analog-digital-conversion of the micro controller input that has a detection range of 0 to 1.1V. To bring the 0 to 5 V of the clamp down to the 0 to 1.1V at the ADC input, the Fluksometer uses a voltage divider with a 1k91 Ohms resistor in parallel to the clamp to ground; impedance and divider and measuring voltage with a little calculating show it works.
5V / 6800 Ohms = 0.000735 A (maximum current flowing at the current clamp)
6800*1910/(6800+1911) Ohms = 1491 Ohms (clamp impedance and voltage divider in parallel - 1/R = 1/R1 + 1/R2 towards the ADC input)
1491 Ohms * 0.000735 A = 1.096 V (voltage at ADC in on full measurement)
If you want to use a different clamp, with different voltage output range or different impedance then you must adapt the voltage divider stage of the ADC input. This you may do completely external to "fake" a 6k8 impedance clamp or change the internal resistor. Or change the controller code, of course, to read, for example 0 to 5V (Atmel controller documentation shows details); but code changes should be out of range.
So, China may help, when you know what you are doing ;-)
Take a "burden" (resistor) and learn about current measurement; the OpenEnergyMonitor project has some nice topics on this - https://learn.openenergymonitor.org/electricity-monitoring/ct-sensors/in... - note: these clamps do not work with the Fluksometer out of the box; they must be adapted as shown above. If you toast your FLM, it is not my fault ;-)
Thanks for the detailed explanation; quite useful ! Two power clamps of 25A are actually sufficient for my needs. Based on the specs above, I found two clamps that would fit :
- JC10F25-V (25A, 0-5V and 6k8 ohms) : https://jdmetering.com/wp-content/uploads/techspecs/JCXXX-V_series.pdf
- DCT-0010-025 (25A, 0-5V and 6k8 ohms) : https://www.magnelab.com/wp-content/uploads/2015/11/DCT-0010-XXX-5-VDC-S...
Would be nice if somebody could cross-check before I order them... Thx
Hm, one issue you still have, the FLM's clamp factors know about 50, 100, 250 A only; thus, using a 25 A clamp would need a 25 A factor or you get the double reading. The jdmetering clamps most likely are those originally used, so better take a 50 A clamp (also in case of peak loads). But just a guess; you may, of course, reprogram the web interface.
Ok thanks for the info; sounds logical. As you might have noticed, I’m not in electronics (not at all BTW...); I’d like thus to avoid burning my Flukso. Instead of adding an additional resistance to a 50A clamp with 6k2 ohms in order to avoid toasting my Flukso (see your previous calculations), I’d prefer a 25A clamp and solve the ratio at software level (don’t even know if it’s possible...). Any idea if that’s realistic...?!?
You won't toast you FLM with the 50A clamp; we are talking about 0.000735 A at 6k8 versus 0.000807 A at 6k2, so, about 1.096V versus 1.18V at reading 50 A; I would call that "within the tolerances" as I doubt that the 6k8 or 6k2 are exact neither the actual output voltage of the clamps themselves (overvolt protection internally is at 7.5V). And the 1.1V reference at the microcontroller is that, a reference. The ADC inputs are tolerant to higher voltages, but the accuracy of reading depends on the selected range, of course; but that is software, too.
And with respect to "realistic", well it is just software, you can actually do anything if you have access to it (what is the actual issue with displaying smaller clamp readings on this very site).
Being "not in electronics" is no excuse to gain some common knowledge, especially in the fascinating world of energy saving ;-) (that's the difference to school strikes and taking things in one's hand)
Hi. I am also looking for V2 power clamps. @Sacha, have you been successful with using a jdmetering device? I am also willing to offer a V3 price for somebody who has V2 spare ones.
What about the V3 power clamps, I guess they could be adjusted to work on a V2 with an additional resistor? However the impedance of the V3 models is not mentioned on the shop page.
Aliexpress and some other websites seem to offer equivalents. Part number is SCT010T-D 50A/5V; note: interfacing with with the FLMv2 requires an impedance of around 6k5 Ohms as described above. And note that the coversion principle of FLMv2 and v3 differs. As such the v3-camps cannot be used directly.