how to connect DAQ to control circuit

[atia_amir]

hye.. I'm still new with LabVIEW. for my final year project I need to develope a system which can monitor seal lead acid battery. I already success in developing the system. but the problem is I have no idea how to connect the system to the battery through NI USB-6212 DAQ card. 

the picture above is the control circuit for my system. from the seal lead acid battery I need to monitor voltage and temperature of the cell. then if the voltage detect less then for example 12V, the relay will trigger to activate charger to charge the battery. if the voltage more than 12V, the relay will trigger to discharge the battery with the load. and the system will stop if the temperature is less for example 20 deg celcius. 

so the problem is how do I connect the NI USB-6212 with my circuit? I really do need help. 

[brian.lee.cc]

Hi Atia,

Are you trying to measure the voltage of your battery directly through one of the AI channels of your USB 6212? From this ni.com link: https://www.ni.com/en-us/shop/model/usb-6212.html, your USB 6212 device has a max voltage range of -10V to 10V. You would need to devise some sort of voltage-divider/translator circuit to divide down your 12V signal to around 10V.

You should perform a web search on what kind of voltage-divider/translator circuits are suitable for measuring batteries. I did a quick search and came up with these links:

http://electronics.stackexchange.com/questions/24170/how-to-measure-battery-voltage

http://www.microbuilder.eu/Tutorials/Fundamentals/MeasuringBatteryVoltage.aspx

However, if you're sampling the battery voltage at a high sampling rate with your USB 6212, you should beware of capacitive effects of using impedance divider circuits.

I assume you want your relays to be electronically controlled by the AO channels of the USB 6212? And what sensors do you plan on using to measure temperature?

Of course, using a 400kS/s DAQ board does seem like an overkill for this application, unless you're just performing some tests. Do you plan to swap the DAQ board out later?

Brian Lee

Applications Engineer

National Instruments

[atia_amir]

hye.. Thanks for the reply..

Yes. I'm trying to measure the voltage of the cell through the USB 6212 and the NI USB that I using exactly the same as in the link you given. Is it mean that I cannot measured a battery which has voltage higher than 10 V. So I think I need to use a cell which has lower voltage than 10 V.

For the temperature sensor actually I'm not decide it yet. Because I'm still not sure the suitable temperature sensor which can be use with my battery which can be connected to the NI USB. Do you have any idea what type of sensor that is suitable to measure the temperature of the seal lead acid battery..??