How to output the same waveform to two channels but with two different amplitudes?

[Mirlo]

Hello everyone,

I have recently connected, through an analog interface, a multifunction DAQ board from Keithtley (KUSB 3116) to an AC power supply (ET, EAC-S2000) that can operate either at constant voltage or at constant current. I have been using Labview 8.5 (btw, it´s my first time with this software) and I managed to read the input signals (voltage and current) using the power supply in manual mode. Up to this point, no problems. However... 

My next step is to try to control the power supply from the computer, making use of the output channels in the multifunction board.

I have been trying to send a normal square waveform to either channel Aout 0 or channel Aout 1, but nothing happens in the power supply (the external control mode was switched on during the attempts, and the frequency was within the range of the power supply). It seems that the power supply needs one channel with maximum amplitude and the other one with a user defined value but I dont know how to do this.

Any help is welcome.

[AnalogKid2DigitalMan]

Mirlo:

Can you post a link or attach the manual for the supply?

-AK2DM

[Mirlo]

This is the manual of the power supply.

[AnalogKid2DigitalMan]

What options (ATI5, ATI10, EXTOS2) does the supply have? Is it a 1 or 3 phase unit?

What connector and what pin numbers on the unit do you currently have connected to your DAQ card?

At first look, I think the supply needs a constant voltage level, not a pulse, on the analog programmin inputs to set voltage and current.

-AK2DM

[Mirlo]

Only the EXTOSZ option is available. Is a single phase power supply. The Multifunction card is plugged to the interface number 3 with a D-sub connector (analog inputs and outputs). The pins connected to the DAQ card are:

1 input Uac set

2 input I set

20 output monitor Ueff

21 output Ieff monitor 

Mirlo 

[AnalogKid2DigitalMan]

Mirlo:

That manual is not very clear. It looks like pins 20 and 21 are analog outputs for the supply, you should not be connecting your analog outs of your DAQ to these.

Pins 1 and 2 look correct, they should be wired to Aout0 and Aout1 of your DAQ card (I'm not familiar with the Keithly DAQ).

If you have a volt meter, set you analog output channels to a steady voltage an verify they are working propery without the supply connected. This is to ensure no damage was done to the card when wired to the output channels of the supply.

What you then need to do is connect the Analog Output Common or Ground of your DAQ card to the supplies GND pin (either 13 or 25 looks like it should work).

-Hope this helps

AK2DM

[Mirlo]

AK2DM:

It is true that pins 20 and 21 are analog outputs for the supply (inputs for the board). But, according to the seller, there is no problem connecting these to the board, since the power supply divides the signal (i.e. 500 V output equals to 10V output in these cables). The real signal is applied to a specimen not to the board. 

I will try to use a volt meter and check the output channels of the board. Also, I will study how to connect the analgo ground of the board. As you can see I dont have too much experience on this subject.

Thanks 

[Mirlo]

Hello again,

I checked with a multimeter and the analog outputs of the DAQ board seem to work fine.

Applying (with labview) steady voltage values in both channels of the DAQ board and measuring with a multimeter between pins 1(Aout 0) and 13(GND) and 2(Aout 1) and 13(GND), I get constant values in both channels.  By the way, I did check and confirmed that the ground connection in the D-connector is welded.

I also applied a waveform to both channels with a very low frequency and again the output channels of the DAQ board work fine.

Therefore it seems that the powersupply does not read the signal that I am sending with the DAQ board.

Any more suggestions? 

[AnalogKid2DigitalMan]

Mirlo:

Sounds like your DAQ card is working. About the only information I could find in the manual was a bit confusing:

Selecting the wave form

 Standard signals are selectable with the buttons SINE, SQUARE and TRIANGLE.  The external signal is selectable with the button EXTERN. The signal is transmitted via the interface connection on the back of the device. The intensity of the signal must be adjusted with the rotary pulse encoder AC VOLTAGE.  The signal will be used for 50% if set to 50%. The signal will be used for 100% if set to 100%. It is necessary to consider the maximum frequency of 1000 Hz!

Did you select Extern? Sounds like you can't control the intensity via DAQ, just the waveform profile.

All I can suggest is to contact the manufacturer directly for assistance.

-AK2DM

[Mirlo]

Thank you for all the responses. I contacted the commercial guy and he thinks that pin 14(Udc set) has to be used instead of pin 1.

Hopefully everything will be fine next week.