Multifunction DAQ

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supply control system

Hi, I would like to develop a multiroom supply control system...

In this system, I want to control sveral load's supply of each room...

The control part I still can handle, but I would like to inspect the supply status(on/off) of each load on the front panel.........

I tried to use encoder to define the load status, but i failed when more then one load's supply failure at the same time....

Could anybody give me some suggestion?





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Message 1 of 8

Hi Kelvin,


Can you elaborate on how the supply status (on/off) is monitored in hardware and in your VI?

I don't understand how you used encoder to define the load status.


It would be helpful if you can post a screenshot of your implementation of this part.


Guo Min

Applications Engineer 


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Message 2 of 8



Let said I have 9 loads of each room, I using relay to switch on the input of encoder when the loads is fail to function...

I have to use decimal to binary encoder(4 output), then I need 4 input of DAQ to detect the signal....

But I may havn't enough input port to do more than that....

could u suggest me other more effective way to done this....thank you very much





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Message 3 of 8

Hi Kelvin,


I'm understanding your scenario this way:

You have 9 supplies of loads (e.g. 9 conveyor belts) to a room. When any of these supplies fails (i.e. 1 of the conveyor belts breaks down), a relay will switch on the corresponding input of the encoder.


Please correct me if I'm wrong.


I'm not sure how a decimal-to-binary encoder works. Can you explain?


Best regards,

Guo Min 

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Message 4 of 8



Yes, u are correct, my application is something like that...

A encoder consists 10 inputs(decimal) and 4 outputs(binary)

when the load fail, it will switch on relay to give a 5 volt input to the encoder...

for example the input no. 7 is activated, the output of encoder will be given as 0111...

(1=0001; 2=0010;3=0011 and etc)

then I conect the binary output to the DAQ and then i can know which load is fail...

but i dun know whether is work or not........



best regard,



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Message 5 of 8

Hi Kelvin,


One problem I can see in your design is when more than one supply fails at the same time.

It seems that your encoder is only designed to work when only one input can be HIGH at one time. Have you considered that?


I would suggest using DI channels of your DAQ to directly monitor the relay. This will need 9 DI channels for each room, but it eliminates the pitfall of using an encoder. 


In terms of increased channel count, you may consider our industrial DIO devices with up to 96 channels. Simply search for USB-6509, PCI-6509 or PXI-6509 in the search box.


Best regards,

Guo Min 

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Message 6 of 8

Hi Guo Min,


Yes, I know that encoder can only detect one input only....

So that I try to find other design....

If I still want to use the DAQ(USB 6009), is it got any other suggestion? 

Is it possible by using the PLC replace the DAQ can done this?



Best regards



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Message 7 of 8
Hi Kelvin,
I can only think of these two designs:
1. Use a decimal-to-binary encoder so that you need 4 DI channels for each room, but you will only be able to detect 1 supply failure at a time.
2. Use 1 DI channel for 1 supply so that you can detect multiple supply failures, but you will need 9 DI channels for each room.
The USB-6009 that you want to use has 12 DIO channels and 8 AI channels. Therefore you can monitor up to 20 supplies using one device.
If you are monitoring more than 2 rooms, you'll need to use multiple USB-6009, or other devices with higher channel counts. 
You can also use PLC to monitor them instead. The benefit is that PLCs are expandable, so you won't have any limitation of channel counts, but the cost per channel is normally higher.
Guo Min 
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Message 8 of 8