B&K Precision 1823A - Manual - Manual (Page 21)

21
5-3. Line Frequency Measurements
Use of the attenuator, low pass filter, and/or x10 probe is advisable when
measuring line frequency because the high amplitude signal and noise can
cause wrong counting.
WARNING
USE CAUTION IN MEASURING THE LINE FREQUENCY OF AN AC OUTLET.
USING THE PROBE TIP ONLY, MEASURE BOTH SIDES OF THE LINE. THE
GROUND SIDE WILL GIVE A ZERO READING AND THE HOT SIDE WILL
PROVIDE THE DESIRED MEASUREMENT. DO NOT USE THE "GROUND
"LEAD OF THE PROBE. REMEMBER THAT THE CHASSIS OF THE
COUNTER AND THE
“GROUND” LEAD OF THE PROBE ARE ALREADY AT
EARTH GROUND (VIA THE 3-WIRE POWER CORD OF THE INSTRUMENT).
TOUCHING THE
“GROUND "LEAD TO THE 'HOT" SIDE OF THE LINE WOULD PLACE A
DIRECT SHORT ON THE POWER LINE THROUGH THE PROBE CABLE,
RESULTING IN POSSIBLE INJURY AND DAMAGE TO THE PROBE CABLE.