Devices with interfaces like Ethernet (RMII) that also work with 10/100 Mbps speed require a relatively low 25/50MHz clock output. The clock, in most cases, is generated either from an external crystal, or an internal or external clock generator that runs asynchronously to the tester clock. Besides measuring the frequency of those output clocks, it is also necessary to measure the Random Jitter (RMS Rj). The UltraFLEX family offers a fast Walking Strobe measurement capability on the UP1600 and UP2200 to measure the random jitter (Rj) as well as data dependent jitter (DDJ) of output signal edges. Unfortunately, a clock period that is a few picoseconds faster or slower than the expected period, can cause the measurement to fail, especially when many sites need to be tested in parallel, since each crystal has a slightly different frequency. This presentation will demonstrate some limitations when measuring Rj jitter on low frequency clocks using the Walking Strobe method. It will provide possible methods on how to test sites in parallel with an efficient test time using different setups and methods. Finally, it will compare the different methods in terms of accuracy and test time.