How to control NORDAC (SK 250/1 FCT) through Labview by CB-50LP block connected with Computer through NI PCI-6251?

[Microwinner]

First, thanks for any help. My situation is like this: (I attached the pictures for the block and NORDAC Vector Connector.)  

The Analog inputs (pin 7 -, pin 8 +) from NORDAC Vector mc Frequency Inverter (SK 250/1 FCT) were connected to pin 23 and 21 of CB-50LP block individually. The analog input voltage range is 0-10 V. The NORDAC Vector was used to control the gear pump.

Now I would like to control NORDAC Frequency through adjusting Analog inputs voltage, which is Analog output Voltage for LabView program. The CB-50LP was connected with computer through PCI-6251 board.  Therefore, I developed a AO task in LabView program to control theAO voltage to further control the Frequency Inverter. Unfortunately, I could not manage it.    

What I did is  like the following:  

I tested both of the AO channels (AO0 and AO1) available from device of PCI 6251. I set the signal generation mode as ‘1 demand’. Both of them can run but does not change the Voltage Analog Output. Then I checked the voltage between pin 23 and 21 on CB-50LP block, the voltage was always 3.768 V if I switch on the power for the NORDAC Vector. This value does not vary even when I try to increase the Frequency manually. But When I check the Voltage of the Analog Output Voltage of NORDAC Vector, this value changed according to the Nordac Frequency.    

My questions are as following: 

1)      Am I right to control the NORDAC Vector through the way mentioned above?

2)      If so, why did the Analog  output voltage from Labview signal generation  still the same, even when I change the output control value?

3)      In this case, I suspect maybe the NORDAC Vector was wrongly connected to CB-50LP.   Is there anybody here knowing the details of CB-50LP  I/O connector?

Fianlly, any suggestions would be appreciated. Thank you.

Houxue

[Microwinner]

Two pictures are shown as following

CB-50LP block

NORDAC Vector mc Frequency Inverter (SK 250/1 FCT)

[moderator1983]

On CB-50LP:

pin 23 --> Analog Output Ground

pin 21 --> Analog Output Channel 1

pin 20 --> Analog Output Channel 0

Are you sure that you're using 'AO channel 1' and not 'AO channel 0'..?? Read the voltage across 23 (ground) & 20 (AO-0), while running your code...!!

Ohh it seems you already checked channel 0 as well...!!

can you share the code, just generation part...!!

[moderator1983 · Accepted solution]

Also you can refer to this link.

[Microwinner]

Hi moderator,

Thank you for your suggestion. The link you gave to me was very helpful, which was exaclty what I am looking for. Based on the pins I/O connector of M68-50, the AO1 channel of PCI6251 was the right one. As a result, I could control the AO voltage by Labview. For example, when I generate a voltage of 5v by labView, the same value was detected between pin 21 and 23 of CB-50LP as well as pins 7 and  8 of NORDAC. So I think the voltage generation part is fine. However, I could not control NORDAC frequency through the AO voltage.  Therefore, I suspect the problem exists in NORDAC part.

After inquring with the technician of NORDAC, two suggestios were provided:1) connect pin 21(AO1)  and pin 23 (GND) of CB-50LP to pin 8 (Analog Input +) and p6 (GND) of NORDAC seperately. 2) change the Analog input function to monitor model.(P400-2). Neither of them works.

the connection system was shown as following.

 My code for the AO voltage output was attached. Could you please have a look at it? Thank you very much.

[moderator1983]

Its LabVIEW (at many places you had written LabView or Labview).

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@Microwinner wrote:

when I generate a voltage of 5v by labView, the same value was detected between pin 21 and 23 of CB-50LP as well as pins 7 and  8 of NORDAC. So I think the voltage generation part is fine. However, I could not control NORDAC frequency through the AO voltage.  Therefore, I suspect the problem exists in NORDAC part. 

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So now, you're able to control the voltage and that voltage is appearing across NORDAC as well.. so that part is working fine.. and you're right, problem seems to be exits in NORDAC part.

Now one doubt I have is, are you sure this hardware (NORDAC) is configured to accept Analog Signal and not Digital...??? check following parameters (in this PDF😞

a. Page-14 P400 (Analogue input function )

b. Page-14 P401 (Analogue input mode)

c. Page-12 P104 (Minimum frequency)

d. Page-12 P105 (Maximum frequency)

Also why don't you think to use digital input (to NORDAC) mode, as that has fine control over frequency

[Microwinner]

Thank you.

First, from the data sheet of NORDAC, I find the Analog Input Function. So I thought it should be fine to control NORDAC with LabView. But I am not sure.

Regarding the digital input control, as far as I know, DI can only vary between two values (i.e. 0, 10V). Therefore the setpoints are discretized. Correct me please if I am wrong.

However, what I need is to control the pump frequency through fine increasement, so continous signal input is prefered. What do you think?

By the way, I am contacting with the Technician from NORDAC.

Thank you.

[moderator1983]

I believe, with DIGITAL INPUT (TTL max 5 volts), basically we need to feed a variable frequency pulse train to NORDAC.

But you can confirm it with NORDAC technicians.

[Microwinner]

All right. But TTL signal is not suitable for my pump controlling. Cause I want to control the frequency continously. Suggestions from NORDAC is ongoing. Thank you lot.