Because the frequency meter can go down to sub-audio frequencies, it uses a DC-coupled input. But to make sure that both bipolar and unipolar signals can be detected, the threshold that is used to detect the signal is above ground. It is expecting a signal that goes up to at least 1.25 volts and down to at least 0.7 volts. So a unipolar signal (one that is only above ground) that goes down as low as 0.7 volts will trigger it, and a bipolar signal (one that goes plus and minus around ground) that goes at least up to 1.25 volts will trigger it.phutureboy wrote:Hi Dave, quick question I have here:
For some reason I have tried my O'Tools+ with an Arturia MiniBrute and all waveshapes are displayed perfectly in Scope Mode, but when in Frequency/Tuner mode the O'Tools+ doesn't seem to react with the saw or square waves, only with the sine or triangle wave. As if square and saw were silent...
Any idea what could cause this to happen ?
So if the signal is very small, or if it is biased very far positive or negative then it won't trigger the frequency meter. For a signal like that you might want to first run it through another module that boosts it, like a buffer, mixer, or other type of amplifier. Or maybe something that adds a bit of bias to it.
The reason there are two threshold voltages (the signal has to go above the upper threshold and then fall below the lower threshold) is so it can reject noise on the signal in order to get a more accurate reading. Otherwise noise could throw off the reading and it would be less accurate.