How to read digital signal using NI6025e+NI PCI-1200 Adapter

[kcYEOH]

Hi all, sorry to say that i'm new to DAQ card and i'm encountering a problem and i'm hoping someone can help me out. I'm using NI-6025e with PCI-1200 adapter, and i know these are products are quite old but no choice, i was provided with these equipment only.

I need use them to read digital signal from another peice of measurement tool. The measurement tool will give high bit of 5V and low bit of 0V and i need to use NI6025e with PCI-1200 adapter to read this digital signal.

I have to tap two wires from the output of the measurement tool to PIN 22 and PIN 13 (DGND) of the PCI-1200 adapter and i expect i will get the digital signal through my software. But i did not get any reading at all.

So may i know am i connected to correct PIN of the PCI-1200 adapter in order to read the digital signal?

Helps and advise are appreciated.

Thanks in advance.

[Dennis_Knutson]

The PCI-1200 is a stand alone DAQ device and is not an adapter nor does it have any relationship to the 6025e.

The pin you are using is Port B bit 0 and should work just fine. What are you using to read the data at the pin? Did you specify the correct device?

[kcYEOH]

Hi Dennis, thanks for the reply. There is a adapter conversion for Ni-6025e and here's the infor :http://sine.ni.com/nips/cds/view/p/lang/en/nid/11027 

I tapped one wire_A at Port B bit 0 (PIN 22) and another wire_B at PIN 13 (DGND). The first wire_A is come from digital output of my measurement tools and the wire_B is come from analog ground of my measurement tools. And when i check with multimeter by tapping the same point at my instruments too, it gives reading of 5V.

I'm using NI-6025E and my software is visual basic referenced with DAQ.dll. When i read input value using the DIG_In_Prt of port B, it's returning 255, it's correspond to 11111111, which meant all bit of Port B is high? But i do not connect to other bit except bit 0 of Port B.

So is my hardware connection correct?

Please advise..

[Dennis_Knutson]

I don't see where the problem is. You've verified with the voltmeter that you have a logic high and that is what you are reading. Set the input to 0 volts and do a read.

You are using the function to read all bits of the port and if you have nothing connected, the inputs will float to a logic 1.

[kcYEOH]

Hi Dennis, what i meant here is when i tapping the output signal of my digital output of my measurement tool, it shows 5V which is high bit. So my measurement tool is giving the correct signal.

But i can't read the digital signal using my vb applications from the DAQ when my measurement tool is connect to the PIN22 and PIN 13(DGND). It's always showing 8 bit high (255). So my question is, can you please check is my wiring correct (by tapping the analog ground of measurement tool to my DAQ digital ground)?

Besides, i expect to read a value of integer 1 (00000001) when i connect my measurement tool to the digital pin of the DAQ card. How can i do that? Is it a must to connect all the 8 bits even though i'm just using a single bit?

Additionally, i can actually sending digital signal to control my measurement tool through the same DAQ and same VB applications through Port A.

Please advise and thanks in advance.

[Dennis_Knutson]

I still do no see your problem. You should be reading 255 when pin 22 is connected to a 5V signal and the other pins of the port are not connected to anything. If you insist on using the Dig_In_Prt and want to read 00000001, then you would have to ground the unused pins. Otherwise, use the Dig_In_Line function for just bit 0.

You might also consider upgrading to DAQmx instead of the obsolete traditional DAQ that you are using now.

[kcYEOH]

Hi Dennis, i took your advise and i'm using Dig_In_Line to read single bit digital signal. When i try to ground the PIN 22, it's show 0 and when i'm not connect everything, it's always showing 1. And now i know there is nothing wrong with my software coding and it's just that i need to connect correctly in order to get the signal.

However, here comes my second questions. Let said i have voltage supply which given 5V when it's ON and 0V when it's OFF. I have tried to make a direct wire connection from the positive terminal of my voltage supply to this PIN 22 to and negative terminal to PIN 13 (DGND) of my DAQ.

But when i turn my power supply ON or OFF, it's always showing high bit of 1. Actually i just trying to stimulate the digital signal of high or low by supplying 0V or 5V.

So may i know what i can do in term of wiring in order to read the 0V and 5V as digital input? I just need a simple wiring connection that will works because i'll just using it for data collection.

Please help and thanks in advance.