sensoring the liquid level at the PCB

[sujeep]

Hi,

The liquid level detectors (silicon diodes) are mounted in a PCB as an array. The PCB in kept inside the cryogenic container in an upright position to measure the liquid level. The active length of the PCB is 400mm. The number of sensors is 80 and the gap between the sensors is 5mm.

I hv done this using for loop in C programming.

int is=5,y6fs=410;
 for(i=0;i<=79;i++) /*Draw Sensors [80 in no.] on the board for region*/
 {
         line(50,y6fs,100,y6fs);
  y6fs=y6fs-is;
 } 

In labview cn I do this using a graph.

[TroyK]

Are you just looking for a visual representation of the fluid level? Why not use the tank indicator?

What are your inputs? What do you want as an output?

Message Edited by Troy K on 07-04-2007 06:34 PM

[sujeep]

Hi

The inputs are constant current, digital inputs, voltage and the out should be the liquid level in the cryogenic fluids. 

[TroyK]

So you have 80 digital inputs? They can just be displayed as an array of booleans...

Or you can convert it to a number and display it in a tank fill indicator as I mentioned earlier like this...

Message Edited by Troy K on 07-06-2007 01:05 AM

[sujeep]

Hello Sir,

I am making using of current (i.e., SCC-C020)  which is connected to the PXI DAQ-6251. And 8 digital outputs from the SCC-68 and this is also connected to PXI DAQ-6221. And 8 digital outputs are from the PCB board. This PCB is inserted into the cryogenic fluids in the upright position and I need to find at which sensor in the PCB is the liquid level.

So if I am using the Boolean array will it be Ok . If so cn u explain me how to do this. I am new to labview and Measurement & Automation. So hope u cn help me.

Thanks in advance.    

[Dennis_Knutson]

You have yet to explain how these 80 sensors are connected to the DAQ board. You just said that you only have 8 digital outputs from the PCB. Do you have 80 or 8 sensors? If you really have 80, you need to explain how things are wired to a DAQ board with only 16 singnle ended analog inputs and 24 digital I/O.

For an introduction to DAQmx, look at http://zone.ni.com/devzone/cda/tut/p/id/5434.

[TroyK]

Alright sujeep I'm going to take a guess at how you are measuring the liquid level (seeing as you haven't really given us a good description).

(Assume schottky diode for the reverse leakage current that increases with temperature) All the diodes are wired in parallel and as they are submerged into the cryogenic liquid their temperature drops significantly and so does thier reverse leakage current. By measuring the current through your circuit you can tell how many diodes are submerged in the liquid.

Does that sound close enough? You detect the fluid level by taking one current measurement?

Then you want to display the fluid level on the screen from 0mm to 400mm in 5mm steps?

You should be able to scale the current you measure to give you 0 to 400. Then display it as I suggested in my first reply.