Vantek CA5015 electronic load, is it crusty? or is it me :) - Page 1
Forum section: electronics / testgear

author: lk
author_rank: Regular Contributor
timestamp: March 27, 2013, 07:47:06 am
content: Greetings,I needed at electronic load, which could handle up to 5 amp and beyond, so building my own would not be worth it. Anyway,so i bought thishttp://www.precisegauge.com/index.php?main_page=product_info&cPath=111&products_id=501.It looked like an ok buy, but what i have noticed is that i quickly get massive voltage drops, at 2 amps drawn my the voltage drops 3-4 volt. even at low current the voltage drop is significant.and in constant power mode its just sillythe voltage drops the same way meaning that the while the voltage drops the current increases, which means that the voltage drops further, more current and so on.What am i trying to say with this? I would suggest not buying this electronic load, as it seems to be rubbishDoes anyone else have this electronic load in a version that works? maybe i was just unlucky, i cant return it, i have had it too long without having the need to use it.-lk

author: Rerouter
author_rank: Super Contributor
timestamp: March 27, 2013, 07:56:31 am
content: umm.. not to sound silly but would the massive voltage drops not be due to your moderate impedence voltage supply and wires? as the load itself is meant to apply a load not generate a voltage :?

author: Balaur
author_rank: Unknown
timestamp: March 27, 2013, 08:01:58 am
content: Quote from: lk on March 27, 2013, 07:47:06 amSorry, but I don't really understand. What you are using as a power source? A lab power supply, a battery? Did you mean that the voltage provided by that source drops by 3-4V when the load is drawing that current? How is this an indication that the electronic load is not functioning correctly?In constant current mode, are you able to check through (a series) multimeter that the current in the circuit is constant for any voltage input?The constant power mode is certainly meant to keep the product of the voltage and current constant.Best regards

author: lk
author_rank: Regular Contributor
timestamp: March 27, 2013, 08:07:58 am
content: Hi Rerouter, that could be, it would be no surprise that the error/misunderstanding is in my end:) would not be the first time.But i would still not expect to see a voltage drop over 2-3 volt over a 2 foot cable of 18AWG, 50 mV would make more sense. The lab powersupply happily stays at the 2 amps, its does not break into sweat.-lk

author: Rerouter
author_rank: Super Contributor
timestamp: March 27, 2013, 08:10:08 am
content: once again hoping to not sound stupid, but could your lab supply possibly have a current limit? or it may have a thermal limit in which case either set it to its maximum voltage or minimum voltage and see what happens,

author: lk
author_rank: Regular Contributor
timestamp: March 27, 2013, 08:42:22 am
content: Hi Balaur,I most likely have no idea what im doing. But perhaps i should make a video of thisBut anyway let me try to explain what i would expect to see.This is in reference to daves test of the Korad PSU in EEVblog episode 315. time code in linkhttps://www.youtube.com/watch?feature=player_detailpage&v=Fya-4mjV4N4#t=938sDavesKorad at 31.00 Volt and 4.9 A and the BK precision electronic load is at 30.9V and 5ALKs setupLabPSU at 12.00 volt and 2A and the vantek CA5015 is at around 7 volt and 2A.I would expect the voltage at the load to stay close to 12 volt, and not sag, but i could be wrong, i purely base this on what i observe from Daves video-lk

author: lk
author_rank: Regular Contributor
timestamp: March 27, 2013, 08:47:46 am
content: Hi Rerouter,The lab powersupply is not in current limiting mode, as far i can see. But i have not measured the voltages at the source, to see if there is a surprise there. I dont think its thermal shutdown, as this is a problem from the starts, and the fans have not turned on in the powersupply or the load for that matter. Myabe there is a tiny black hole in the load that just absorb my voltages-lk

author: mzzj
author_rank: Super Contributor
timestamp: March 27, 2013, 08:48:37 am
content: Quote from: lk on March 27, 2013, 08:07:58 amAre you trying to say that Vantek displays lower voltage than it should?Just use multimeter to check how much voltage you actually have at the Vantek connector terminals. Better that way so that wiring resistance and possible error on lab power supply doesn't affect your results.I have to say that this model looks intresting as it has very wide input range, so I am really interested to hear more of your experiences.

author: Balaur
author_rank: Unknown
timestamp: March 27, 2013, 09:02:40 am
content: Quote from: lk on March 27, 2013, 08:42:22 amWell, it's certainly intriguing to find such a huge difference difference between the supply and the load measurements.Frankly, everything could be a suspect: load, cable, connectors or power source.Based on previous experience, I would suggest that the loss is on the cable itself. Maybe the 18AWG is too optimistic (especially if bought already assembled with connectors and everything). I've bought some pre-made alligator cables that were supposed to be around that size as well, and I've found that the actual wires only had a few strands of copper.Alternatively, the assembled cable may have (or may have developed in time) issues on the cable to connector interface.There is actually a very simple way to find out: use a multimeter to measure the voltage directly (as close as possible) on:- the power supply connectors- on the electronic loads connectorsThis way, you will have a very clear idea on where the loses are. If the load indications are way off, then sure, it's regrettable.In any case, the correct functioning of an electronic load in constant current mode should be verified by adding a multimeter in series with the power source and the power load, setting a current value on the load and varying the source voltage. The current should remain constant in the whole nominal interval.

author: BravoV
author_rank: Super Contributor
timestamp: March 27, 2013, 09:44:51 am
content: If its me, I'd bring my car's battery and those thick low resistance car jumper wires if you have it, definitely will clear things up whether its the psu or the dummy load's fault.

author: saturation
author_rank: Super Contributor
timestamp: March 27, 2013, 12:27:24 pm
content: Those Vantek's don't look very well made; they look like copies or rebadged 'Beich' models. See the Array thread on details on how to test eloads:https://www.eevblog.com/forum/testgear/array-electronic-loads/45/If you can take photos on the internals it would help.

author: Kevin.D
author_rank: Frequent Contributor
timestamp: March 27, 2013, 12:59:56 pm
content: To test the "burden resistance" of your e.load and cables it need's to be not current limiting ,just set your power supply to 10 V or something and set your current limiter on your power supply to 1A then set your e.load current limit to a higher value .( so it's your power supply thats doing the current limiting.)then just test the voltage drops on your cable's and across the output terminals of the e.load .It should be 0.8 ohm for the e.load according to the specs on there web page.

author: lk
author_rank: Regular Contributor
timestamp: March 27, 2013, 04:36:02 pm
content: Yay, turns out im the supplyer of crustyness in this case, i had a cable that had a resistance of atleast 2 ohm, it was bouncing around. so it might be more. The cables i use there have between 0.002 and 0.005 ohms of resistance.Now the constant Power/Resistance works for me aswell, so turned out Rerouter was correct. And im happy he wasthanks to everyone-lk

author: SeanB
author_rank: Super Contributor
timestamp: March 27, 2013, 06:44:57 pm
content: I have had some OHL test leads that were better as heaters than as test leads, some were good as noise sources as well, being very microphonic. Some got "tested" on a car battery till they burst into light, smoke and flame as a finale. Some were so bad they survived this, but did not survive going through the leaf shredder.