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App Notes

Software & Driver

 

4.3.4 - Analog Outputs

The IOType to set the voltage on an analog output is:


LJ_ioPUT_DAC

The following is a special channel, used with the get/put config IOTypes, to configure a parameter that applies to all DACs:

LJ_chDAC_BINARY

Following is example pseudocode to set DAC0 to 2.5 volts:


//Set DAC0 to 2.5 volts.
ePut (lngHandle, LJ_ioPUT_DAC, 0, 2.50, 0);

9 comments

I have a U3_lv

The LJ_ioPUT_DAC seems to program an 8-bit voltage but the device has a 10-bit dac. Is there a different iotype for 10-bit commands?

You mean that you are seeing 20 mV steps?  Make sure you have a current UD driver and U3 firmware.  Go to the "config defaults" section of LJControlPanel and make sure 8-bit DAC mode is not selected.

 

Yes. I see 20mV rather then the 5mV expected. The firmware is 1.32 appears to be up to date. The driver is 3.15, seems to be up to date too. (I was not able to run 3.24 for some reason). The 8-bit mode is not selected. 

What sort of problem do you have with the 3.24 installer?  I would tackle that so you are using a current driver before you do much more troubleshooting.  Perhaps post a comment on that page with the problem.

After we get your driver updated, can you test the DACs using the test panel in LJControlPanel, if that is not what you are doing already?

 

Also, confirm that LJCP reports hardware version 1.30 for your U3.

 

When I send 5.0 to my U6 I get 0v out. I have had to cap at 4.9 to ensure an output voltage.

Do your DAC troubleshooting with no load on the DAC.  Do you see this using the test panel in LJControlPanel?  How are you measuring the voltage output?

What firmware version are you using?

Which interface method, modbus?

You might try upgrading to the latest firmware: http://labjack.com/support/firmware/u6

I am using a U6 device.

Can the value of the Analog Output be read back?

ie there is

ePut(lmHandle, LJ_ioPUT_DAC,0,2.50,0) as above to set the Analog Output

is there an equivalent eGet command to read the output

Regards