The comparator circuit shown within this schematic:
**broken link removed**
has the following issues. I realize that the oscillation may be cause by the lack of hysteresis, but don't understand the reason for the issue with the low discriminator window pot adjustment. I need to ask the author of this text what he means by "low component":
The lower pot (on the PC board) is actually the high discriminator window (it’s mislabeled on the PC board). Turn this pot clockwise until you begin to hear clicks. (It’s a 20 turn pot.) As you continue to turn it, the click rate will increase. However after a certain definite point the comparator will begin to oscillate, so back it off of that point. This pot adjusts the window for the maximum pulse height. Clockwise allows higher pulses through, counterclockwise blocks them. This is the more useful of the two pots.
The upper pot (again mislabeled) adjusts the low discriminator window. Turning this pot counterclockwise blocks the smaller pulses. That was the theory! However it seems that there is only a narrow range where this might occur. Turning it too far counterclockwise will block the higher pulses as well because they have a low component. So much for theory. Note that the two windows are ‘ANDed’ so a pulse must pass through both windows before it will register as a click.
**broken link removed**
has the following issues. I realize that the oscillation may be cause by the lack of hysteresis, but don't understand the reason for the issue with the low discriminator window pot adjustment. I need to ask the author of this text what he means by "low component":
The lower pot (on the PC board) is actually the high discriminator window (it’s mislabeled on the PC board). Turn this pot clockwise until you begin to hear clicks. (It’s a 20 turn pot.) As you continue to turn it, the click rate will increase. However after a certain definite point the comparator will begin to oscillate, so back it off of that point. This pot adjusts the window for the maximum pulse height. Clockwise allows higher pulses through, counterclockwise blocks them. This is the more useful of the two pots.
The upper pot (again mislabeled) adjusts the low discriminator window. Turning this pot counterclockwise blocks the smaller pulses. That was the theory! However it seems that there is only a narrow range where this might occur. Turning it too far counterclockwise will block the higher pulses as well because they have a low component. So much for theory. Note that the two windows are ‘ANDed’ so a pulse must pass through both windows before it will register as a click.
