How do I ground a signal connected to an SCB68 pin board

[tkdnutter@yahoo.com]

Hello everybody

I have a ICP signal conditioner (model 480B21) and a SCB68 connector board.  I really don't have a clue how to ground the signal.

Any help and I would be really grateful

Dave

[devchander]

To which DAQ card is your SCB 68 connected??

[Jesse_O]

Hello Dave,

I am not exactly sure what you are looking for, however you may find your answer in the following documentation.

1.  Field Wiring and Noise Considerations for Analog Signals

2.  How Are E Series DAQ devices Grounded?

Regards,

Jesse O.
Applications Engineering
National Instruments

[tkdnutter@yahoo.com]

The DAQ board that I am using is the PCI-6052E and the output of the signal conditioner is as following:

supply voltage VDC 25~30

supply current mA DC 3.0 (+/-0.25)

[devchander]

you mean you want to connect VDC 25~30 to an AI channel of your DAQ card directly????

I strongly suggest that you do not do it. This would surely damage your card

That card can only measure in range of +/-10V

Here are the maximum overvoltage protection figures for this card

Overvoltage protection

Powered on .................................±25 V

Powered off.................................±15 V

[tkdnutter@yahoo.com]

Oh, sorry the sensor excitation voltage is 27V and the output voltage is less than 3V.

Message Edited by tkdnutter@yahoo.com on 02-01-2007 02:10 AM

[Jesse_O]

Hello Dave,

If you look in the first link I posted previously at Table 1 you will see several diagrams for both floating and grounded signal sources.  It explains the best option for connecting them.  The best option would be to perform a differential input.  To determine how to connect this to your SCB-68 you can find the pinout of your device.  You can also create a task in MAX and see the connection diagram.  I have attached a screenshot of what a connection diagram in MAX might look like below.

I hope this answers your question,

Jesse O.
Applications Engineering
National Instruments

[tkdnutter@yahoo.com]

Dear Jesse

First of all I would like to thank you for all your help. I now know that I am suppose to connect the negative end of the signal conditioners power supply to the pin 34 and the positive end to the 68 pin.

But where is the negitive terminal on my signal conditioner? I can't find it. Well, I don't know what it is. So I have attached a link to a picture and the specifications of the signal conditioner.

http://www.davidson.com.au/products/vibration/pcb/conditioner/480b21.asp

To connect from channel 1 to the pin 68 on the connector board I have used a BNC cable and cut it in half and split it, so I can connect to pin 68. I know that I need to ground the signal by connecting something up to the pin 34. But what do I connect it from? Where is the negative terminal?

Dave

PS Sorry to be such a pain in the ass as I don't have a clue...

[devchander]

If it is a single core BNC cable, usually the inner core cable can be connected to positive terminal of channel and the outer shielding/webbing can be connected to the negative or ground terminal

[Jesse_O]

Hello Dave,

From the link you posted, it looks like the part you are using has BNC outputs.  You can either find a way to connect the BNC cable inner cable and gnd to the daq card(i.e. BNC to alligator), or use a terminal block that has BNC inputs.   The SCB-68 is a screw terminal block and you will need access to the individual wires on the BNC cable. 

You can find the available terminal blocks here.

Regards,

Jesse O.
Applications Engineering
National Instruments