Dear Roger,
I don't know the true meaning of gain lock. For example , when the amplitude of signal is 2V, what is the effect when using GL1V?
Thank you
Good afternoon kangle2miao,
The DT800 has 11 gain stages from 10 mV up to 20 V.
By default when the DT800 is acquiring data it takes a sample and checks the reading to make sure it is in range. If it isn't it then changes the gain and samples again. It will do this several times to get the best accuracy for the reading.
When we measure a frequency we don't care what the amplitude is just the point it crosses the threshold point (usually zero). By setting the gain to lower than the maximum signal we will clip the top of the signal which basically gives us a square wave. This should get rid of the noise that can cause false readings in the lower range.
Cheers,
Roger
Dear Roger,
When I measure signal with amplitude greater than 1V, the part greater than 1V becomes 1, while the rest becomes zero .Am I right?
Good morning kangle2miao,
When measuring a frequency you only need to points of reference on the frequency. The easiest points to pick are when the signal crosses the zero point in the same direction. That is the frequency is measured from the inverse of the time between two rising edges when the signal passes through zero.
Cheers,
Roger
Then what is the difference when I use GL1V and other gains ,Gl10mv , for example?, since what you say.
Dear Roger,
You said "By setting the gain to lower than the maximum signal we will clip the top of the signal which basically gives us a square wave. This should get rid of the noise that can cause false readings in the lower range."
Then I want to know when frequency measurement works with sine, saw tooth, etc.
Thank you
Good afternoon kangle2miao,
The rate of rise from negative full scale to positive full scale will be much faster. Also as the resolution is higher the signal to noise level should be better. (Which is why I recommended that you try different gain levels.)
But you can also set the threshold level (Offset from zero) so if you lock the gain to less than the threshold you won't see the crossing.
Cheers,
Roger
