I am not an electrical/electronic engineer, so please bear with me.
I have a monochromatic camera (www.qimaging.com/resources/pdfs/QICAM-12bitManual.pdf) which can be triggered (i.e. capture image) by a 5v TTL signal provided by an external triggering system (a function generator). Also, the camera comes with an electronic triggering board related to this application (www.qimaging.com/resources/pdfs/ExtTrigApNotes.pdf) (www.youtube.com/watch?v=LuC_-cUO97c). So, the function generator output is not directly connected to the camera. The BNC cable from the function generator would be first connected to the triggering board; then the triggering signal will reach the camera through a circular DIN port. One thing this triggering board does is it allows you to monitor the exposure time and readout time of the camera (so I think this is one way to see if the camera is triggered or not, right?).
So, basically I want to feed the camera a 5v TTL square signal (DC) and make the camera capture an image (i.e. trigger) on edge high mode. I also, have an external light source, supplying the required light for the image, which also need to be synced with the triggering TTL signal on edge high mode (www.hsps.com/2006/pages/nanodren.htm).
I have come across a few issues for which I need help from you:
1) I am using a function generator with an in-built TTL output (BNC connection). So, when I monitor the function generator output, the voltage amplitude is not 5v, but around 4.2v. That persists even if I set the function generator's impedance to High Z. I tried two different function generators and I get the same 4.2-4.4v. What's the reason behind this? How can I get an exact 5v TTL signal?
2) You may ask, your camera surely works (will trigger) even with a 4.3v signal. You are right. But it gets problematic when I also connect the external light source (required for higher quality image) to the function generator to be triggered at the same time as the camera. So, when the BNC cables from the function generator output is connected to the oscilloscope, my voltage is around 4.3v, but the moment I connect another BNC cable to the same output in the function generator and plug its other side to the external light source, the voltage amplitude drops to around 3.6v (probably due to internal impedance of the external light source), which may not enough to trigger the camera.
So, although the function generator might be giving out a 5v signal when there is nothing attached to it, but this surely drops to a value of 3.6v with all the BNC cables connected to it. My question is that how I can make sure a 5v signal (DC square) will reach both my camera and my external light source.
Please let me know if you have other suggestions for my case. Hope my post won't get deleted due to not following the forum guidelines. Thanks in advance.
Note: internal impedance of the function generator is 50 ohm.