On the TDS1000 and TDS2000 series scopes+ for the trigger frequency readout+ do we have a frequency counter inside the oscilloscope or just the same measurement method as auto measurement with higher resolution?
Yes, there is an autoranging frequency counter built into the products. This feature provides the Trigger Frequency Readout capability of the TDS2000/1000 Series oscilloscopes.
It is capable of providing 6 digits of useable resolution over the entire frequency range of 10Hz to the bandwidth limit of the trigger source.
The Trigger Frequency Readout provides accuracy of 50PPM time base accuracy + 1PPM quantization error. This specification is a typical specification, therefore is not warranted.
The Trigger Frequency Readout updates four times/second, and works by counting both qualified trigger signals and time base clocks until either the time base or the trigger counter is half full. At the next qualified edge on the slower signal, acquisition stops and the ratio is calculated and displayed. There are always more than one million counts in the count chain having the quantization error, thus providing the additional 1PPM error. Additional error sources relating to signal to noise ratio, trigger hysteresis and signal slew rates exist, but are very complex to calculate, and have been ignored.
Trigger signals can be qualified by the Pulse Width Trigger function, allowing separating a train of pulses into various categories by width.
Trigger Frequency Readout does not operate in video trigger mode.
In general, the Trigger Frequency Readout should provide a stable value to frequencies in excess of 200MHz, channel bandwidth and/or signal amplitude permitting.
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