ETS-Lindgren HI-3604 ELF Survey Meter - Manual (Page 38)

Page -- 30 HI-3604 Manual
Frequency Measurements
Connection of a frequency counter to the waveform output jack
allows immediate measurement of the frequency of the applied
magnetic field. To perform this measurement, a portable digital
multimeter (DVM) capable of measuring frequency maybe used
with the HI-3604 to, for example, determine the vertical refresh
rate on a VDT. To perform this measurement, an analog signal
sufficient to drive some frequency counters may require that the
HI-3604 be placed in fairly strong field.