Daq 6259 and Power Supply Interface Connection

[NguaHoang]

Good afternoon NI Engineers,

I use the Daq 6259 OEM to turn on or off the power supply which it has external on/off. Please see the attached for more details.

Here are my questions:

1. If the return line of power supply (RTN) doesnt connect with the digital return line of Daq 6259 (DGND), then the digital output of Daq 6259 (DIO) is unable to turn on or off the power supply.

2. If the return line of power supply (RTN) connects with the digital return line of Daq 6259 (DGND), then the digital output of Daq 6259 (DIO) can turn on or off the power supply. The total current goes throught the load is 8 Amperes. Does the Daq 6259 get damage ? Does the Daq 6259 get hot?

Thanks for your support.

NguaHoang

[Bueller]

I'm afraid that the current connection will damage your DAQ device.

You need a circuitry that will limit the current going into the DAQ device. A high resistance circuit netween the RTN and DGND might be a possible solution.

Regards,

Faris

[NguaHoang]

Hi Faris,

I like to thank you for your advise. How many Amperes can the return current go through DGND of Daq 6259?

Thanks and Best regards,

NguaHoang

[AnalogKid2DigitalMan]

I looked at the schematic, I do not see any issues. The DAQ card should be fine.

Faris- The digital output of the DAQ is simply providing a TTL compatible signal to the power supply enable input. The return line for the 28V is what is handling the high load current.

[Bueller]

AnalogKid2DigitalMan- it's true that the DAQ is providing a TTL compatible signal to the power supply enable input,  but what worries me is the return current (8 A )to the DGND, especially that I don't know how internally the RTN and  the SENSE lines are connected internally.

However, if the connection when the RTN connected to DGND was tried and it worked,then it should be fine, but connecting a resistor at DGND would still be a good idea to limit the current sinking at that pin.

If the connection haven't been tried yet, I recommend studying carefully thr value of the current returning to the DGND before trying such a connection.

Regards,

Faris A

[NguaHoang]

Hi Faris,

Thanks you for your advises.

I used a 100 ohms resistor between the RTN and DGND. The voltage crosses the 100 ohms resistor is about 0.3 volt so that there are 3 mA going back to the NI device. Is it okay?

Thanks and Best Regards,

NguaHoang

[Bueller]

NguaHoang,

I hope you had a nice weekend. The device cn handle the 3 mA.

Good Luck in your application

Regards,

Faris A