Keysight U1251B Guide De Démarrage Rapide page 16

4 Probe the test points and read the display.
5 If the reading is unstable or zero, press
6 The signal is out of range if the reading is still
–
WARNING
–
16
to select division of input signal frequency by
100. This accommodates a higher frequency
range of up to 20 MHz.
unstable after step
Use the frequency counter for low voltage
applications. Never use the frequency counter on
AC power line systems.
For input more than 30 Vpp, you are required to
use frequency measurement mode available under
the current or voltage measurement instead of
frequency counter.
Keysight U1251B and U1252B Quick Start Guide
5.