RIGOL DM3068 - Manual (Page 158)

RIGOL Chapter 6 Specifications
User’s Guide for DM3068 6-12
[3] Relative to calibration standards.
Measuring Characteristics
Frequency and Period
Measurement Method
Reciprocal-counting technique, AC-coupled input using the AC voltage function.
Input Impedance 1 MΩ ± 2%, in parallel with <150 pF capacitance on any range
Input Protection 750 V rms on all ranges
Measurement Considerations
All frequency counters are susceptible to error when measuring low–voltage, low–frequency signals. Shielding inputs from external noise pickup is critical for
minimizing measurement errors.
Settling Considerations
Errors will occur when attempting to measure the frequency or period of an input following a dc offset voltage change. The input blocking RC time constant
must be allowed to fully settle (about 1 s) before the most accurate measurements are possible.