First and foremost, my main job is not programming, but I know a little.
I have a 450 mV single ended signal. I want to average a number of samples and display that number in a text box using VB 6.0.
Parameters are: sample input (AIN0) for one second, average those samples, multiply by 11.11 and display in textbox for 500 milliseconds (format x.xx), clear if necessary, loop until exit button is pressed. I do not need a start button, it can start when the form opens, unless it clears out a buffer or something.
I would like to do this for 5 inputs, not sure if one HV is enough to do that.
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We provide VB6 examples here:
https://labjack.com/support/software/examples/ud/visual-basic
U3_Simple and U3_AllIO are good examples to look at. Our examples are more for demonstrating using the UD driver/API with the U3 and does not get indepth on the GUI side, so you'll want to refer to VB6 Form documentation and tutorials online if you need something more advanced GUI wise.
General UD function documentation can be found here:
https://labjack.com/support/datasheets/u3/high-level-driver
On the U3-HV you can use 5 analog inputs. AIN0-AIN3 are dedicated high-voltage analog inputs, and the rest of the FIO and EIO lines can be configured for low-voltage analog inputs:
https://labjack.com/support/datasheets/u3/hardware-description/ain
https://labjack.com/support/datasheets/u3/hardware-description/fio
I understand how to open the U3, get an AIN reading and display things in boxes. What I can't find is how to take an AIN value, store it somewhere and then average the readings. I see it for a T7, but can't find it for a U3. Do I have to stream to get an average?
Also, I am using the HV because of the +/- 10V inputs, as my voltages can get down to 900 microvolts minimum. I think I read somewhere that it can accurately read down to 500 microvolts?
The U3 does not support any averaging in hardware. Rather your software needs to acquire multiple points and then average them. You can either acquire multiple command-response reads (the simplest way would be to make multiple calls to eAIN in a for loop) or use stream mode to get a bunch of reads:
https://labjack.com/support/datasheets/u3/operation
The U3 is a 12-bit device, so the basic resolution of the +/-10V inputs is about 5 mV.
What is the max voltage of your signal?
The max volt I need to read is 450 mV... but if it's only 5 mV resolution that won't work for me. I don't know why I thought it would. I would have to amplify it at lease 5x in order for the unit to read properly... Which is what I was trying to get away from. I could have up to 700 or 800 mV, so amplifying it by up to 10 should be less than the 10V threshold... I have an extra U3 LV but I suppose I would need another HV for 8 V or so...
Since your max is only 450 mV, you could use a low voltage analog input instead (FIO or EIO). The normal range is about 0-2.4 volts, so resolution is more like 600 uV.
To improve on that with the U3, you want to add an LJTick-InAmp. Or move up to the U6 or T7 (or better yet the -Pro version of either) to get much higher resolution and a built-in amp:
https://labjack.com/support/datasheets/t-series/appendix-a-3-1