Hi Guys,
I am working on a project for my PhD where I want to measure the power consumption of different electric wheelchairs during different tasks. Now I am looking at the best way to monitor DC current and voltage in a non invasive way. It has to be non invasive because some of the wheelchairs we will use during the experiments are rented so I can't start opening up wires ( apparently they don't like that :D). Now I was looking at some DC clamp meters, but the issue is that I will need analog output to store my data and carry on my analysis afterwards and this seems to raise the price a lot!
I was wondering if you know of any clamp type DC current and voltage sensors I could use.
There are some Honeywell current sensors that I have experience with. http://sensing.honeywell.com/product-page?pr_id=54672
I've used a CSLH3A45 45A hall effect sensor with good effects. It's a pass-through one, but doesn't open. There are some similar choices from Tamura at Mouser in the $15 to $30 range.
Although the Honeywell sensor I have is not designed to come apart, it;s easy to pry the plastic case off and slip the hall-effect current transducer out. I suppose you could hack the clamp part of a cheap clamp meter to place the Honeywell current transducer in the loop and re-calibrate the sensor with the new core. It would be worth sacrificing a $20 current sensor and a $20 cheapie clamp-meter to see how well it worked.
Giulia86:
I can't start opening up wires ( apparently they don't like that :D)
I would think that this type of equipment always has user-replacable batteries and ones that are always VRLA type with bolt-on terminals. I would think that rental or not, you should be able to get into the main negative lead of the battery pack and insert a current shunt.
Another problem is that I will need to move the sensors between different wheelchairs after each experiments, so the changhe should be as quick as possible (unfortunately I have limited time in the lab!). This is one of the reasons I was thinking to use clamp sensors. I have never used a hall sensor before and this is probably a really silly question: after I opened the plastic case will the current trasducer be in a close ring as well? (will I have to open it before placing it into the calmp part)?
Giulia86:
after I opened the plastic case will the current trasducer be in a close ring as well?
The Honeywell sensor I am familiar with consists
-- of a ferrite ring that has notch cut right through it, just wide enough for the current transducer to fit into
-- the current transducer is a three-pin device resembling a flattened transistor
-- a plastic case into which the ferrite core and transducer fit. The case keeps the parts together and in the proper orientation and has the tabs for mounting the device.
The pictures on page 7 show what you're up against, roughly.
It looks like all the CSL series use about the same current transducer and just have different core arrangements.
Well, they look to have a analogue voltage output proportional to the sensed current, as near as I can tell. You'd be measuring that from the Adruino via an ADC input. It looks that they have a supply voltage of +12 to +15. This might have to be precision regulated. The output looks to be centred on 5V, maybe varying between 0V and 10V. To read this in the 5V referenced Arduino ADC is going to require a voltage divider.
when I supply 12v to sensor, I read 4.1v at output, when 2a current pass through hole, there is no change in the output voltage,still 4.1v.Sadly, how can I read the output voltage.Maybe, should supply it with symetric +-15v
